Influence of Femtosecond Laser Parameters and

Lasers Manuf. Mater. Process. https://doi.org/10.1007/s40516-018-0059-1

Influence of Femtosecond Laser Parameters and Environment on Surface Texture Characteristics of Metals and Non-Metals – State of the Art A. Bharatish 1 & S. Soundarapandian 1

Accepted: 5 April 2018 # Springer Science+Business Media, LLC, part of Springer Nature 2018

Abstract Enhancing the surface functionality by ultrashort pulsed laser texturing has received the considerable attention from researchers in the past few decades. Femtosecond lasers are widely adopted since it provides high repeatability and reproducibility by minimizing the heat affected zone (HAZ) and other collateral damages to a great extent. The present paper reports some recent studies being made worldwide on femtosecond laser surface texturing of metals, ceramics, polymers, semiconductors, thinfilms and advanced nanocomposites. It presents the state of the art knowledge in femtosecond laser surface texturing and the potential of this technology to improve properties in terms of biological, tribological and wetting performance. Since the texture quality and functionality are enhanced by the proper selection of appropriate laser parameters and ambient conditions for individual application, reporting the influence of laser parameters on surface texture characteristics assume utmost importance. Keywords Femtosecond . Laser surface texturing . Metals . Non-metals

Introduction The high average power (100 mW – 10 W) and repetition rate (1 kHz - 50 MHz) [1] of ultrashort pulsed lasers have brought together the industrial need of high machining throughputs along with quality in terms of scribing holes and producing textures [2, 3]. Conventional pulsed laser processing of materials, typically employing nanosecond and longer pulses results in wider heat affected zone (HAZ) [4–6], formation of cracks due to thermal shock [7, 8], recast layer and dross built at the entrance and exit of the drilled

* S. Soundarapandian [email protected]

1

Department of Mechanical Engineering, IIT Madras, Chennai 600036, India

Lasers Manuf. Mater. Process.

micro holes, holes with high aspect ratio (width to depth), morphological changes [9, 10] and collateral damages [11]. To overcome these limitations, ultrashort pulsed lasers under picosecond (ps) and femtosecond (fs) regimes have become the choice of researchers from past few decades. The advantages include high repeatability, precise control in achieving feature geometry and negligible HAZ [12]. Pulsed fs lasers are mainly adopted for surface modification, drilling and cutting of wide range of materials in automotive, medicine, aerospace, microelectronics, photonics and other industries [13]. The specificity of fs laser machining is fs laser surface texturing (FLST) with the aim of improving tribological, biological, optical and wetting performance of functional surfaces. The process can produce tailored surfaces shaped with high quality and accuracy. Femtosecond laser textured surfaces find wide variety of applications that include thrust bearings [14], journal bearings [15], cylinder liners [16], piston rings [17, 18], concentrated contacts [19, 20], mechanical seals [21], micro fluidic devices [22] and waveguides [23]. Some of the other applications include surface enhanced Raman Scattering (SERS) effect [24], enhanced photodiode performance [25, 26] and magnetic data recording media [27]. However, material removal rate drops in fs regime because of incubation effect i.e. threshold fluence and energy penetration depth reduces with increase in the number of pulses. Also, minimization of surface roughness demands very high marking speeds that are offered only from fast rotating cylinders or polygon scanners [28]. Most often Laser Surface Texturing (LST) and Laser Surface Structuring (LSS) are considered as the same terminologies in the open literature. To state precisely, LST deals with laser induced topographical changes to create specific textures on various materials whereas LSS alters the surface crystallinity and crystal structure. Eventhough some of the reviews on LST [29] and fs laser surface structuring of metals [30] were provided by the researchers, the effect of femtosecond laser parameters and ablation medium on the texture characteristics of both metals and non-metals has not yet been reported so far. Hence this paper reports a state of the art in fs laser induced nano and micro level textures on both metals and non-metals. The effects of femtosecond laser parameters such as fluence, scanning speed and ablation medium on texture performance characteristics of metals (BMetals^ Section) and non-metals (BCeramics^, BPolymers^ and BSemiconductors, Composites and thin Films^ Sections) are presented.

Ultrashort Pulsed Laser Ablation Mechanism Ultrashort pulse lasers have wide potential industrial applications because of their good combination of high processing quality and low cost/maintenance requirements. During laser machining process, the laser beam is absorbed by the target material and the material melts or vaporizes resulting in morphological changes in and around the absorbing region. The physics of laser-matter interaction mainly depends on the laser parameters (fluence, scanning speed, pulse duration, repetition rate), material parameters (absorptivity, heat capacity, thermal conductivity) and process parameters (assist gas pressure, standoff distance). When the laser radiation is absorbed, the material


heating takes place along with melting, vaporisation and sublimation leading to phase transformations. The ablation threshold decreases with pulse duration and proves that the ablation is a thermal process [31, 32]. During the interaction of low intensity short laser pulses with metal targets, the energy transport into the metal can be described by the following one-dimensional, two-temperature diffusion model [33]. Ce

∂T e ∂QðzÞ ¼− −γ ð T e −T i Þ þ S ∂t ∂z

ð1Þ

∂T i ¼ γ ð T e −T i Þ ∂t

ð2Þ

Ci

∂T e ∂z

ð3Þ

S ¼ I ðt ÞAα e−αz

ð4Þ

QðzÞ ¼ −k e

where z is the direction perpendicular to the target surface, Q (z) is the heat flux, S is heat source term, I(t) is laser intensity, A = 1- R is the surface transmissivity, α is material absorption coefficient, Ce and Ci are the heat capacities of the electron (per unit volume) and lattice subsystem respectively, γ is the parameter characterizing the electron-lattice coupling, ke is the electron thermal conductivity. The three characteristic time scales electron cooling time (τ e ¼ Cγe ), lattice heating time (τ i ¼ Cγi ) and pulse duration (τL) are deduced from Eqs. 1–4. Hence, three regimes of ablation are defined as: (i) Ablation with Nano pulses (τL ≫ τi) : There is enough time for the thermal wave to propagate inside the material and eject the greater amount of melt. Ablation is considered as solid – liquid – vapour transition. The ejection of liquid melt results in HAZ which is detrimental to material properties. Collateral effects such as microcracks, burr and recast layer spread the interaction area limiting the machining precision. (ii) Ablation with Pico pulses (τe ≪ τL ≪ τi): Laser ablation is accompanied by electron heat conduction and formation of melt. Electron cooling is mainly due to energy exchange with the lattice. Even though ablation is considered as direct solid – vapour transition at the surface, the presence of liquid melt greatly reduces the precision and accuracy of machining. (iii) Ablation with Femto pulses (τL ≪ τe): Cooling of electrons takes place rapidly due to energy transfer to the lattice and heat conduction to the target. Ablation is considered as direct solid - vapour transition. Lattice gets heated in picoseconds which results in direct vapour and plasma followed by rapid expansion in vacuum [34]. Hence, minimum energy is transferred to the material and results in controlled HAZ, heat rate and interfacial velocity [35]. Interaction of fs pulses with target material is highly non-linear which results in high pulse intensities allowing the fabrication of minute structures [36]. The classification of lasers based on pulse duration regime and peak power is as shown in Fig. 1 [37]


Fig. 1 Classification of lasers based on pulse duration regime and peak power [37]

Texturing Techniques The techniques for creating textured microstructures on the contact surface of the workpiece include direct beam, scanning and interference methods. In direct beam method, the laser beam is directly focused on to the material surface through ablation head, which moves in controlled increments as shown in Fig. 2a [38]. In scanning method, the laser beam is reflected through galvanometer and quickly moved to the desired position for each microcavity to be created as shown in Fig. 2b [39]. In interference method, two beams interfere with each other to create parallel grooves as shown in Fig. 2c. J Chen et al. [40] investigated the influence of laser parameters such as beam diameter, pulse fluence, wavelength and number of pulses on the texture of aluminium surface by forming laser interferometry patterns. X Jia et al. [41] fabricated nano patterns on ZnO crystal by adjusting the laser polarization combinations of multi-beam interference.

Fig. 2 a Direct beam method [38] b Scanning method [39] c Interference method [40]


Effect of Femtosecond Laser Parameters Metals The effect of critical femtosecond laser parameters such as laser fluence and scanning speed, pulse parameters such as pulse duration and the number of pulses, ablation medium/environment on various texture characteristics of metals are reported. Fluence Titanium alloy (Ti – 6Al – 4 V) is one of the most commonly used metal alloys in biomedical applications. The surface treatment of titanium based alloys affecting implant surface topography and chemistry can improve osseointegration of human mesenchymal cells and hence increases the life span of implants. Femtosecond laser surface texturing of Ti - 6Al - 4 V based biomedical implants has received great attention by researchers. Cunha et al. [42] analysed the effect of laser parameters on human mesenchymal stem cell shape, cell density and bimodal roughness distribution of Ti - 6Al - 4 V based dental and orthopaedic implants. Fluence in the range of 0.3– 0.4 J/cm2 caused the formation of Laser induced periodic surface structures (LIPSSs) and nanopillars (NPs). At a higher fluence of 0.8 J/cm2, microcolumns covered with LIPSSs were observed as shown in Fig. 3. Also, reduction in the cell area and focal adhesion area were found on the laser-textured surfaces than on a polished reference surface. The same authors [43] extended their study to analyse the surface topography and wettability characteristics of Ti - 6Al - 4 V. Increase in fluence from 0.4 to 2 J/cm2 lead to the formation of columnar microtexture due to rise in intensity of ablation. The effect of average fluence (0.1–0.3 J/cm2) on the surface was characterized by the presence of ripples perpendicular to the beam polarization direction. Thus, formation of LIPSS and nanopillers during the femtosecond laser texturing of Titanium alloy surfaces reduced the colonization of Staphylococcus aureus and the subsequent formation of biofilm [44].

Fig. 3 Laser induced (a) and (b) periodic surface structures, (d) and (e) nanopillers, (g) and (h) micro column textured surfaces in Ti-6Al-4 V [42], with permission


Mutlu E et al. [45] reported that, unlike the picosecond and nanosecond pulses, femtosecond texturing lead to nanoscale roughening of Ti - 6Al - 4 V surface at low fluence (around 0.04 J/cm2). This was mainly attributed to thermal effects that occurred during long pulse regime which washed away the fine nanometer scale features. The incident power of 1.4 W, repetition rate 43 MHz, pulse duration 300 fs, scan rate 4 mm/ s and spot diameter 10 mm were considered. B J Li et al. [46] investigated the influence of laser fluence (0–18 J/cm2) on wettability contact angle and surface roughness of titanium surface using Ti: sapphire femtosecond pulsed laser. With increasing laser fluence, the period of the microspikes significantly increased due to the higher molten material in laser irradiated zone as a result of higher peak power intensity of fs pulses. Also, nanoripples exhibited a slight irregular change in the range of 550–600 nm. The stable period of the ripples was mainly because of the periodicity of LIPSSs approximately equal to that of plasmon wavelength which in turn depended on laser wavelength and material attributes. Thus, only ripples were formed at average fluence around 0.1 to 0.3 J/cm2 but increasing the fluence till 0.8 J/cm2 caused the formation of microcolumns covered with LIPSSs mainly due to the presence of higher molten material in the laser irradiated zone of Ti-6Al-4 V alloys. Also reduction in the cell area and focal adhesion area that could improve the osseointergation of cells were found on the laser-textured titanium surfaces than on a polished surface. Aiming at behavior of cells on laser modified surfaces at the micron and nano levels of steel and other metals, M M Calderon et al. [47] reported the formation of longitudinal and transversal LIPSSs on stainless steel surface at 2.71 J/cm2 fluence and 1 mm/s scanning speed resulting in 30 pulses per spot. J Y Edwin et al. [48] analysed the effect of fluence (32–1096 J/cm2) and number of scans (1–30) on surface texture of 304 stainless steel. While low fluence regime (< 130 J/cm 2) was characterised by ellipsoidal cones covered by nanoparticles, columnar and chaotic structures were formed at higher fluences (> 130 J/cm2). But, J Stasic et al. [49] found that lower fluence of 0.66 J/cm2 was found to be sufficient for inducing surface modifications on AISI 1045 carbon steel in both single pulse and scanning regime. Thus, for precise control over the cell distribution and migration at the nanoscale, stainless steel required higher fluence (2.71 J/cm2) but AISI 1045 carbon steel required lower fluence (0.66 J/cm2) when compared with Ti-6Al-4 V alloys. Considering aluminium (2024 T3 and 1100 T0) alloy, K Dou et al. [50] found that fluence (0.08–1 J/cm2) at constant pulse duration formed small separated and cotton like fragments ranging from tens to hundreds of nanometers as compared to the unirradiated samples. This was confirmed by K M T Ahmed et al. [51]. They found that high pulse fluence (1552 J/cm2) resulted in micro-structure development for both titanium and stainless steel, while only trenches were observed on aluminium and copper. When the effect of repetition rate on pulse fluence of copper and stainless steel was studied [52], increase in repetition rate from 1 to 10 kHz resulted in the decrease of threshold accumulated pulse fluence of copper whereas on Ti, linear trend was reported. At the constant number of pulses, increase in depth and diameter of texture with increase in pulse fluence was reported [53]. Aiming at wettability analysis of aluminium, copper, titanium and Plexiglas, A I Gavrilov et al. [54] investigated the influence of pulse energy (2–10 μJ) and line spacing (24 μm and 12 μm) on the surface geometry of using 1030 nm, 300 fs


ytterbium doped fibre laser followed by hydrophobization. Eventhough the maximum energy density remained same for all these materials, lowest contact angle with the absence of roll off angle was observed in the aluminium sample whereas highest contact angle and lower roll off occurred for copper samples. Scanning Speed Scanning speed is one of the important laser parameters which significantly influences the surface roughness, ablation depth and microstructure of metals and non-metals. Formation of LIPSSs, nanopillers and microcolumns were reported at medium (5 mm/s), higher (25 mm/s) and lower scanning speed (1 mm/s). Also increase in scanning speed lead to decrease in surface roughness and human mesenchymal cell density of Ti-6Al-4 V based orthopaedic implants [42]. Focusing on wettability characteristics, Cunha et al. [43] reported that laser textured surfaces exhibit a transient behaviour. At t = 0 s, surfaces treated with scanning speed of 0.1 mm/s were not wetted by water but wetted by HBSS (Hank’s balanced salt solution). Best wetting was achieved for surfaces treated with scanning speed in the range of 0.1–0.01 mm/s for both water and HBSS. Thus, laser treated surfaces had high affinity and hydrophilic behaviour towards HBSS. O.Raimbault et al. [55] investigated the influence of scanning speed, polarisation direction and number of laser passes on cell response and wettability characteristics of Ti - 6Al - 4 V. They found that increase in the number of laser passes at lower scanning speed (250 mm/s) and parallel polarisation lead to increase in groove depth, surface roughness and decrease in groove width. Significantly, the influence of LIPSS at the initial stages of the cell response was critical than at the confluent cell layers. Thus, higher scanning speed caused smoothening of the surface. This was supported by N G Semaltianos et al. [56]. They investigated the influence of fluence (0.28–30 J/cm2), scanning speed (1–10 mm/s) and number of overscans (5–90) on surface ablation features of nickel-based superalloy C263. They reported that lower roughness with higher machining depth could be achieved by low average power density determined by higher scanning speed and higher overscans as shown in Fig. 4a, b. With the increase in average power density, microscopic holes (pores) with average dimensions of 300–400 nm appeared mainly due to a state of extreme non-equilibrium followed by ultrafast non-thermal heating by the femtosecond pulses. With the increased number of overscans, the period of the lines along which the holes were aligned became higher and higher scanning speed resulted in higher surface finish thus eliminating the formation of pores. Some of the studies showed that higher surface roughness can increase the number of cells adhering to the substrate and cell activity. According to Y H Jeong et al. [57], fs laser textured Ti-35Nb-xZr alloys showed higher surface roughness (0.139 μm) than that of non-treated Ti-35Nb-3Zr alloy (0.099 μm). Same authors also evaluated hydroxyapatite thin film coatings deposited on nanotube-formed Ti–35Nb–10Zr alloy for surface morphology and wettability characteristics [58]. Hence, in almost all the metals, increasing the scanning speed caused lower surface roughness resulting in higher groove depth and lower groove width. Environment Some of the authors have reported the effect of laser parameters on ablation characteristics and microstructure of metals when immersed in liquid, inert gas and air medium. B K Nayak et al. [59] reported the influence of laser fluence and ambient gas (SF6 and HCl gas) on the microstructure of titanium. The texture formation


Fig. 4 Effect of average power density and peak fluence on (a) surface roughness (b) ablation depth of Nickel based super alloy C263 [56], with permission

was significantly influenced by the presence of gases as shown in Fig. 5a, d. Lower gas pressure favoured the formation of taller, sharper and conical pillars under constant fluence. Structure formation also took place during irradiation in air but the features were not as sharp as that under inert medium. Under distilled water, C A Zhulke et al. [60] investigated the influence of type of structure, peak fluence and number of pulses on surface characteristics of Grade 2 Titanium and 304 Stainless steel. Plastron lifetime when submerged in distilled water or synthetic stomach acid was critically dependent on the specific degree of surface micro and nano roughness, which can be tuned by

Fig. 5 Effect of various ambient conditions at fluence 2.5 Jcm−2 and laser shots 280 of Titanium (a) Vacuum (b) air (atmospheric condition) (c) 100 mbar SF6 (d) 100 mbar He [59], with permission


controlling various laser parameters. Using ethanol as ambient environment, Bashir et al. [61] reported the formation of irregular grooves embedded with nanoscale droplets of about 200 nm size and craters at a higher fluence of 11.8 J/cm2 as shown in Fig. 6a. Increase in pulse duration from 25 fs to 100 fs at constant laser fluence lead to the distinct growth of nanostructures as shown in the Fig. 6b. Corresponding structural modifications were reflected in Raman shift information as shown in Fig. 6c, d. Laser nanotexturing of W finds application in the fabrication of improved field emission cathodes. In ethanol, E V Barmina et al. [62] investigated the effect of delayed femtosecond pulses on nanotexturing of tungsten. Maximum of ripple period was achieved at the same time delay of 1 ps at which nano structure attained minimum. Catalina Albu et al. [63] investigated the low spatial frequency and high spatial frequency LIPSS formed on Ti, Cr and W metal samples immersed in air, ethanol and water. The period of structures formed in liquids was several times smaller than those formed in air. This was probably due to a transient modification of the dielectric permittivity and lower periodic thermal gradients created in liquids due to the ultrashort excitation of the material. Also, deeper depths were achieved in liquids when compared to air. This was probably due to the formation of mechanical pressure in liquids during femtosecond laser irradiation that can increase the LIPSS depth and the fast cooling effect due to the liquid environment which will freeze the structures. The summary of the research works carried out on femtosecond surface texturing of metals is as shown in Table 1.

Fig. 6 a Irregular grooves with nano scale droplets at 11.8 J/cm2, b Growth of microstructure at 100 fs, Tetragonal rutile structure of SnO2 at c) 25 fs, 1000 pulses d) 11.8 J/cm2,1000 pulses [61], with permission

Lasers Manuf. Mater. Process. Table 1 Summary of prior work on femtosecond laser texturing of metals Ref

Laser

Material

Repetition rate (kHz)

Pulse duration (fs)

Wavelength (nm)

Observation

[42–44] Yb:KYW

Ti - 6Al- 4 V 1

500

1030

Laser induced periodic structures, Nanopillers and microcolumns

[55]

Yb:KYW

Ti - 6Al- 4 V 100

400

1030

Laser induced periodic structures

[45]

Yb:KYW

Ti - 6Al- 4 V 43,000

300

1035

Nanoscale roughening

[50]

Excimer

Aluminium

0.01

500

248

Small separated and cotton like fragments

[51]

Ti:Sapphire Ti, SS304, Al, Cu

10

100

800

Trenches on aluminium and copper at 1552 J/cm2

[61]

Ti:Sapphire Tin

1

25–100

800

Irregular grooves embedded with nanoscale droplets

[48]

Ti:Sapphire SS304

10

100

800

ellipsoidal cones covered by nanoparticles and chaotic structures

[47]

Ti:Sapphire AISI304

1

130

800

Nanopatterned surfaces with LIPSS

[53]

Titanium gem

Beryllium Bronze

1

40

800

Texture diameter was not influenced by higher number of pulses

[49]

Ti:Sapphire AISI 1045

1

160

775

Optimised laser fluence (0.66 J/cm2)

[52]

Ti:Sapphire Cu, Ti

1–10

100

800

Dependency of repetition rate on pulse fluence

[59]

Ti:Sapphire Ti

1

130

800

Taller pillars at lower gas pressure

[60]

Ti:Sapphire Grade 2 Ti and 304 SS

1

80

–

Dependency of plastron lifetime on micro/nano roughness

[54]

Yb doped fibre

0–2000

300

1030

Lowest contact angle for Aluminium, highest contact angle for Copper

[46]

Ti:sapphire Ti

1

130

800

Microspikes and nanoripples

[57, 58] Ti:sapphire Ti-35Nb-xZr

1

184

800

Higher roughness (0.139 μm) for laser textured Ti-35Nb-xZr alloys

Ti:sapphire Nickel-based 1 super alloy C263

180

775

Porosity elimination at low average power density, higher scanning speed and higher overscans

[56]

Al, Cu, Ti, Plexiglas

Ceramics Ultrashort pulse laser produces high peak power intensities and provide energy to the material before thermal diffusion [64]. This advantage makes laser textured ceramic


surface free from spatter or resolidified material. The effect of fluence, scanning speed and lubricants on textured alumina, various carbides and nitrides have been reported. Fluence Considering tungsten carbide tool inserts, Anis Fatima et al. [65] reported that increase in laser fluence from 2 to 102 J/cm2 caused an increase in kerf width and kerf depth. Also, taper angle increased with decrease in fluence as shown in Fig. 7. There was no significant change in hardness for every fluence at higher scanning speed. This was attributed to shorter interaction time associated with high scanning speeds. Maximum material removal rate could be achieved at highest fluence and lowest scanning speed. Also considering the effect of groove spacing Y. Lian et al. [66] found that single pulse energy of 2 μJ, scanning speed of 1000 μm/s and scanning spacing of 5 μm could achieve best nanograting quality. The period of the nano gratings increased with decrease in single pulse energy and rise in scanning speed as shown in Fig. 8a, b. Micro-grooves parallel to the main cutting edge had adhesion area reduced to one third when compared with non-textured tool. The study was also extended to analyse five types of cemented carbides and the authors found that the average values of the texture period were between 660 nm and 670 nm. Scanning Speed Surface roughness of the femtosecond laser textured ceramics play a major in achieving optimal scanning speed. According to Anis Fatima et al. [65], kerf width and kerf depth were found to decrease with the increase in scanning speed. Surface roughness decreased when scanning speed was reduced from 20 mm/s to 0.5 mm/s. Groove distance also played a major role in tool performance. According to P. A Barbosa et al. [67], surface roughness decreased by 29.3% and 39.2% at 200 μm and 300 μm displaced grooves from the cutting edge respectively as shown in Fig. 9a. Machining force was reduced by 27.6% for texture tool at 200 μm from the cutting

Fig. 7 Effect of fluence on taper angle of tungsten carbide (WC) [65], with permission


Fig. 8 Influence of (a) single pulse energy and (b) scanning speed on nanograting period of YS8 cemented carbide [66], with permission

edge (Fig. 9b). Tshabalala et al. [68] investigated the effect of laser power (0.1–0.75 W) and scanning speed on surface roughness of silicon nitride based SiAlON ceramic using femtosecond Ti: Sapphire laser. Unlike metals, highly periodic surface was observed at lower scanning speeds (2–8 mm/s), whereas higher scanning speed caused sharp valleys. Aiming at optimal reflectance of solar absorbers, D. Sciti et al. [69] investigated influence of scanning speed (0.56–5.63 mm/s) at constant repetition rate of 1 kHz on the surface roughness and hemispherical reflectance of TaC. The authors observed that increase in laser speed decreased the laser fluence resulting in the regular appearance of grooves as shown in Fig. 10a. The roughness increased almost five times for specimen having surface finish of 0.2 μm while it was doubled for those having a surface finish of 1 μm as shown in Fig. 10b. The longest interaction with laser also produced the largest increase in absorbance. Thus precise control over the surface roughness and machining force could be achieved by controlling the texture spacing and scanning speed. In nitrides, highly periodic surface was obtained at lower scanning speeds (2–8 mm/s), whereas higher scanning speed resulted in sharp valleys. But in case of carbides, higher laser scanning speed caused regular appearance of textures. Lubricated Environment Recently researchers have proved that surface textures combined with solid lubricants are effective in reducing the friction and wear in dry cutting process [70]. T Sugihara et al. [71] assessed the wear and tribological performance of WC-Co cemented carbide cutting tool by texturing the dimples. Open shape

Fig. 9 Effect of groove distance from the cutting edge on (a) Roughness (b) Machining force in cemented carbide [67], with permission


Fig. 10 a Regular apperance of Grooves b Variation of surface roughness with accumuated fluence of TaC [69], with permission

structures (microgrooves) had superior lubricity compared to close shaped structures (micro dimples). Fabrication of surface textures on rake faces of WC/Co tools during Ti-6Al-4 V turning using femtosecond laser was also reported by N Li et al. [72]. The effect of tungsten disulphide lubricant coating on 120 fs, 1 kHz laser textured WC/TiC/ Co cemented carbide tools were investigated by D Jianxin et al. [73]. The friction and adhesion between chip-tool interface decreased because of the thin WS2 lubricating film on the textured rake face of the tool. The cutting temperature of the textured WS2 coated tool was reduced by 16% compared with that of the conventional one. K Zhang [74] reported the effect of laser parameters on cutting performance of Ti55Al45N coated WC-Co cemented carbide tool. In the case of high speed cutting, the forces were reduced to the extent of 26% in case of nano textured tools when compared to conventional tools. The effect of cutting speed on cutting force and coefficient of friction is as shown in Fig. 11a, b. The antiadhesive effect of textured cemented carbide tool was reported by T Enomoto et al. [75]. D Bhaduri et al. [76] reported the influence of laser parameters on the surface morphology and tribological characteristics of tungsten carbide tool against stainless steel counter body. The extent of material transfer from the SS ball to the patterned WC specimens increased in unidirectional tests

Fig. 11 Effect of cutting speed on (a) cutting force (b) Friction coefficient of Ti55Al45N coated WC-Co cemented carbide [75], with permission


involving higher sliding velocity, while that from the carbide surface to the steel body was not apparent. Thus, the femtosecond laser texturing of tools reduced the friction and adhesion between chip-tool interfaces by maintaining the thin lubricating film on the textured rake face of the tool. Also open shape structures (microgrooves) had superior lubricity compared to close shaped structures (micro dimples). Cutting temperature and cutting forces were reduced with the usage of nano textured tools. The quality of dimples and channels produced using both ns and fs lasers are as shown in Fig. 12a, d. The summary of the research works carried out on femtosecond surface texturing of ceramics is as shown in Table 2.

Polymers Acrylonitrile butadiene styrene (ABS), Polypropylene (PP), Polyethylene (PE), Polymethyl methacrylate (PMMA), Poly dimethyl siloxane (PDMS) are some of the polymers which received greater attention from researchers. Fluence The effect of fluence on pulse width, hydrophilicity, and hydrophobicity of various polymer surfaces was reported. T L See et al. [77] investigated the effect of fluence and number of pulses on the surface morphology and chemical composition of ABS polymer using Ti: Sapphire and excimer laser. The authors found that ablation threshold value was lower for ABS when interacted with the excimer laser (Fth = 0.87 J/ cm2) as compared to the interaction with the femtosecond laser (Fth = 1.642 J/cm2). Thus, ablation threshold value depended on pulse duration of the laser. According to B Wang et al. [78], increase in fluence lead to increase in hydrophilicity of the polystyrene

Fig. 12 Wear tracks generated on (a) dimples and (b) channels produced using ns laser, and on (c) dimples and (d) channels produced using fs laser, on Tungsten Carbide [77], with permission

Lasers Manuf. Mater. Process. Table 2 Summary of prior work on femtosecond laser texturing of ceramics Ref Laser

Material

Repetition rate (kHz)

Pulse duration (fs)

Wavelength (nm)

Observation

[70] Nd:YLF

TaC

1

120

800

Regular appearance of grooves

4

30

775

Machining force was reduced by 27.6%

[71] Ti: Sapphire Tungsten Carbide 1

100

800

Lower taper at 30 μm spot size

[77] Lasea L5

Tungsten carbide 500

310

1030, 1064

Higher sliding velocity lead to increase in material transfer

[72] Yb: KGW

WC-Co cemented carbide

400

190

515

Superior lubricity of microgrooves

[74] Titanium Gem

WC/TiC/Co carbide

1

120

800

The cutting temperature of the textured WS2 coated tool was reduced by 16%

1 [75] Ti: sapphire Ti55Al45N coated WC-Co cemented carbide

50

800

The cutting forces were reduced to extent of 26%

[66] Ti: Sapphire YS8 cemented carbide

1

120

800

Uniform nano gratings at pulse energy of 2 μJ, scanning speed of 1000 μm/s, and scanning spacing of 5 μm

[69] Ti: Sapphire SiAlON

1

100

795

Sharp valleys due to higher scanning speed (> 8 mm/s)

[68] Ti: Sapphire Cemented carbide

surface as shown in Fig. 13a. Hydrophilicity of Polymethyl Methacrylate (PMMA) surface also showed the same trend as that of polystyrene but was observed at the lower fluence of 5.1 J/cm2 with a contact angle of 6.5° [79]. As one of the interesting research work, S Sarbada et al. [80] fabricated the LIPPS on copper surface and transferred onto Poly dimethyl siloxane (PDMS) to achieve super hydrophobic surfaces. It was observed that the contact angle of copper was reduced, immediately after laser texturing and ultrasonic cleaning. This was attributed to the fact that copper is inherently hydrophilic and the surface roughness caused an increase in this hydrophilicity. But after curing of PDMS on the surface for the texture transfer, the copper behaved hydrophobically due to salinization of the textured surface. Thus, increase in fluence on polymer surface lead to increase in hydrophilicity. Hydrophobic metallic surfaces could be achieved by transferring the texture from metallic surface to the polymer surface. Scanning Speed Scanning speed significantly influenced the surface roughness. As observed by B Wang et al. [79], surface roughness of polystyrene was as high as 9.54 μm (Ra) after laser treatment and variation was insignificant at higher scanning speeds as shown in Fig. 13b. PTFE is an artificial hydrophobic but oleophilic polymer and has thermal stability, chemical inertness, and low surface energy of 20 mN/m [81].


Fig. 13 a Variation of contact angle with fluence b Variation of surface roughness with scanning speed of polystyrene [79], with permission

Thus far, some researchers have paid great attention to the influence of scanning speed on superhydrophobicity of PTFE surfaces. W. Fan et al. [81] adopted the femtosecond laser to fabricate micro-grooves and lamellar submicron structures on the PTFE surfaces at low laser power of 25 mW, scanning speed of 3 mm/s and groove spacing of 5 to 25 μm. Thus, lower scanning speed lead to increase in roughness and volume of trapped air of the PTFE surface by inducing the micro-nano composite structure and improving the water and oil repellency. A new combination of PEEK (Poly Ether Ether Ketone) based self-mating articulation was developed for some of the orthopaedic applications such as intervertebral spacer, spinal cage, and cervical disc prosthes [82]. S Hammouti et al. [83] investigated the effect of number of laser pulses on tribological performance of PEEK surfaces at constant laser power (20 mW) and repetition rate (5 kHz). Specific wear rates obtained for dimpled surfaces were ten times lower than those obtained for limited and untextured surfaces. Environment Pulsed laser ablation of polymers in the liquid environment (PLAL) is mainly applied for coating and functionalization of surfaces [84], adhesives [85], drug delivery systems [86], organic photovoltaic systems [87] and smart materials [88]. Daniel E M et al. [89] investigated the various properties of laser ablated Poly bisphenol A carbonate (PBAC) under various liquid media. The effect of laser fluence was first reported in water in the range 0.1–1 J/cm2. The size of round nanoparticles decreased with decrease in the irradiation fluence. Formation of strands in the nanometer scale was reported. T C Chang et al. [90] performed the laser ablation of PMMA, polypropylene and polyethylene under air, methanol and ethyl alcohol conditions. The etch rates and size of hole obtained in methanol and in ethyl alcohol were higher for PMMA but substantially lower for PP and PE when compared with air. The summary of the research works carried out on femtosecond surface texturing of polymers is as shown in Table 3.

Semiconductors, Composites and Thin Films Fluence H Wang et al. [91] investigated the influence of fluence (1 J/cm2 to 1.8 J/cm2), number of pulses (2–100) on surface roughness and distribution of surface spikes. The

Lasers Manuf. Mater. Process. Table 3 Summary of prior work on femtosecond laser texturing of polymers Ref Laser

Material

Repetition Pulse rate (kHz) duration (fs)

Wavelength Observation (nm)

1

100

800

Higher ablation threshold (1.642 J/cm2) in femtosecond regime

[79] Ti: Polystyrene 1 Sapphire

130

795

Increase in surface roughness with scanning speed

[80] Ti:Sapphire PMMA

1

158

778

Hydrophilicity exhibited at fluence of 5.1 J/cm2 and contact angle of 6.5°

[81] Ti:Sapphire PDMS

1

100

800

LIPPS

[82] Ti:Sapphire PTFE

1

300

800

micro-grooves and lamellar submicron structures

[84] Ti:Sapphire PEEK

5

130

800

Decreased wear rate for textured surfaces

[78] Ti:Sapphire ABS

small nano-size spikes were irregularly distributed on the a-Si:H surface due to the low laser fluence and pulse overlap. But, rastering the laser beam across the silicon surface drastically enhanced the formation of crystalline silicon polymorphs compared to stationary-beam irradiation under constant fluence as per Mathew J et al. [92]. In CFRP composites, V Olievera et al. [93] investigated the influence of pulse energy (0.1–0.5 mJ) and scanning speed (0.1–5 mm/s) on the morphological characteristics. Laser tracks produced deep gorges in carbon fibres at the lower fluence of 0.35 mJ and higher scanning speed of 5 mm/s as shown in Fig. 14a. LIPSS were generated when the laser beam was perpendicular to the fibre direction and at the border of the laser tracks when the laser beam is parallel to the fibre direction as shown in Fig. 14b. J Koch et al. [94] reported the influence of pulse energy (0.94 to 2.04 J/cm2) at 0.9 mJ, 30 fs laser pulses at 800 nm on nano textures of gold thin film. Laser fluence between melting and ablation thresholds allowed ablation-free texturing of such metals. N Tagawa et al. [95] investigated the influence of pulse energy (3.3–60 μJ/pulse) and scan velocity (10– 200 μm /s) on tribological performance of DLC thin films using 800 nm and 120 fs, pulse laser. The friction coefficients tend to increase with the RMS height values of the nanotextures as shown in the Fig. 15a. Higher fluence leads to the formation of asperities with greater height as shown in Fig. 15b. J Zha et al. [96] reported the surface nano texturing of F-CNF/PVDF nanocomposites. The fluence was set to 0.5 J cm−2 at a repetition rate of 2 MHz and the displacement speed was fixed at 0.8 mm/s. The measured contact angles did not change with time. Thus, increasing the fluence by rastering the laser beam across the semiconductors may be advantageous in obtaining the crystalline polymorphs. In case of composites, lower fluence (0.35 mJ) and higher scanning speed (5 mm/s) produced deep gorges in carbon fibres. In case of thin films, higher fluence and higher scanning speed tend to increase the height of asperities thus increasing the friction coefficients. Scanning Speed In CFRP composites, the scanning speeds of 1, 2 and 5 mm/s resulted in the removal of epoxy resin leaving the carbon fibres unmodified. On the contrary, for


Fig. 14 Laser tracks produced (a) Deep gorges at carbon fibres (b) LIPSS, at 0.35 mJ and 5 mm/s [94], with permission

0.1 and 0.5 mm/s, the carbon fibres were partially ablated [94]. G Nova et al. [97] investigated the influence of repetition rate (1 kHz to 1 MHz) and scanning speed (0.1 mm/s - 150 mm/s) on absorptance of silicon surface. The textured samples showed an increase in absorptance from 60% to 95%. Low translation speeds (0.1 mm/s) lead to high material removal resulting in highly irregular structures. Higher values of scanning speed (350 μm/s and 1400 μm/s) lead to the development of microstructures. Further rise in scanning speeds lead to minimal interaction between laser pulses and irradiated region of the silicon substrate. In DLC thin films [96], higher scanning velocity lead to the formation of asperities with greater height. Hence, scanning speed plays a major role in controlling the material removal rate and also absorptance of semiconductors. Environment H Yang et al. [98] reported the morphology of silicon surface with nano textures produced under vacuum and distilled water using Ti:Sapphire laser operated at a scanning speed of 2 mm/s and laser power of 800 mW. Single-line scanning of silicon surfaces in the vacuum produced spikes that were wider, taller and more sparsely spaced at the centre of the irradiated area but narrow, short and closely packed at the edges. Catalina Albu et al. [99] investigated the effect of air, water, ethanol and chloroform environments on Cr, Ti and W thin films deposited on Silicon substrates at fundamental (775 nm) and frequency doubled (387 nm) wavelengths. The depth of structures produced in liquids environments was deeper than those produced in air environments. C Radu et al. [100] investigated the effect of wavelengths on

Fig. 15 a Effect of RMS height on Friction coefficient b Formation of asperities at greater heights [96], with permission


femtosecond surface structuring of silicon using fluorine and chlorine precursors as environments. At 775 nm wavelength, the average height of the formed Si spikes for the case of fluorine precursors is 4.2 μm and that with the chlorine precursors was 4 μm. Q Wang et al. [101] investigated the effect of laser focusing depth (0 - 40 μm) and wavelength on the relative reflectance and average spike height of silicon surface adopting Ti: sapphire femtosecond laser typically operated at a central wavelength of 800 nm, a repetition rate of 1 kHz and a pulse width of 35 fs. Average spike height initially increased and then decreased with increase in focal depth (Fig. 16a). The lowest relative reflectance was obtained when the laser focusing depth was 20 mm, where a quasi-uniform cone array like microstructure appeared as shown in Fig. 16b. The summary of the research works carried out on femtosecond surface texturing of metals is as shown in Table 4.

Summary and Scope for Future Work Femtosecond laser surface texturing (FLST) can effectively enhance tribological, optical, biological and wetting performance of both metals and non-metals. As FLST can produce micron and sub-micron scale textures on material’s surface, it is considered as superior technique in automotive, aerospace, biomedical and semiconductor device manufacturing industries. However, the effectiveness of this process mainly depends on laser parameters such as fluence, scanning speed and repetition rate, material parameters (absorptivity, heat capacity, thermal conductivity and density) and also on the most essential environment of ablation. The following conclusions can be drawn from the review of FLST of metals and non-metals. 1. In case of Ti-6Al-4 V alloys, only ripples were formed at average fluence around 0.1 to 0.3 J/cm2 but increasing the fluence till 0.8 J/cm2 caused the formation of microcolumns covered with LIPSSs mainly due to the presence of higher molten material in the laser irradiated zone of Ti-6Al-4 V alloys. Also reduction in the human mesenchymal cell area and focal adhesion area that could improve the osseointegration of cells were found on the laser-textured titanium surfaces than on a polished surface.

Fig. 16 a Effect of laser focusing depth on average spike height b quasi-uniform cone structure at focusing depth of 20 mm [102], with permission

Lasers Manuf. Mater. Process. Table 4 Summary of prior work on femtosecond laser texturing of Semiconductors, composites and thin films Ref

Laser

[99]

Material

Repetition Pulse rate (kHz) duration (fs)

Wavelength Observation (nm)

Ti: Si Sapphire

1

130

800

Wider and taller spikes on silicon surface

[102] Ti: sapphire Si

1

35

800

Quasi uniform cone array like micro structure at laser focusing depth was 20 mm

[94]

Yb:KYW

CFRP

1

550

1024

LIPSS perpendicular to the fibre direction

[98]

Pharos Laser

Si

1000

250

1030

Increase in absorptance from 60% to 95%.

[95]

Customised Gold thin film 1

30

800

Optimised fluence for ablation free textures

[96]

Ti:Sapphire DLC thin film 1

120

800

Height of asperities increased at higher fluence and scanning speed.

[97]

EKSPLA FF3000

250

1030

Dynamic changes in contact angles were not observed

F-CNF/PVDF 2000

2. In order to achieve precise control over the cell distribution and migration at the nanoscale, stainless steel required higher fluence (2.71 J/cm2) whereas AISI 1045 carbon steel required lower fluence (0.66 J/cm2) when compared with Ti-6Al-4 V alloys. At the constant number of pulses, an increase in depth and diameter of texture with the increase in pulse fluence was also reported. 3. In almost all the metals, increasing the scanning speed can cause lower surface roughness resulting in higher groove depth and lower groove width. Formation of LIPSSs, nanopillers (NPs), microcolumns and ellipsoidal cones in Ti, Stainless steel, Al, Cu and W are reported by effectively altering the fluence and scanning speed. 4. The texture formation in metals was significantly influenced by the presence of gases. Irradiation of metallic surfaces under lower gas pressure favours the formation of taller, sharper and conical pillars under constant fluence whereas in air the features were not as sharp. 5. In case of both metals and metallic thin films, deeper texture depths were achieved in liquids when compared to air. This was probably due to the formation of mechanical pressure in liquids during femtosecond laser irradiation that can increase the LIPSS depth and the fast cooling effect due to the liquid environment which will freeze the structures. 6. In ceramics, maximum material removal rate could be achieved at highest fluence and lowest scanning speed. In nitrides, highly periodic surface was obtained at lower scanning speeds (2–8 mm/s), whereas higher scanning speed resulted in sharp valleys. But in case of carbides, higher laser scanning speed caused regular appearance of textures. FLST of cemented carbide tools reduced the friction and


adhesion between chip-tool interfaces by maintaining the thin lubricating film on the textured rake face of the tool. 7. In case of polymers, increase in fluence lead to increase in hydrophilicity. Hydrophobic metallic surfaces could be achieved by transferring the texture from metallic surface to polymer surface. Lower scanning speed lead to increase in roughness and volume of trapped air of the polymer surface (PTFE) by inducing the micronano composite structure and improving the water and oil repellency. 8. The etch rates and size of hole obtained in methanol and in ethyl alcohol were higher for PMMA but substantially lower for polypropylene and polyethylene when compared with air. 9. Increasing the fluence on silicon surface may be advantageous in obtaining the silicon crystalline polymorphs. In case of composites, lower fluence (0.35 mJ) and higher scanning speed (5 mm/s) produced deep gorges in carbon fibres. In case of thin films, higher fluence and higher scanning speed tend to increase the height of asperities thus increasing the friction coefficients. Eventhough experimental studies on femtosecond surface texturing of metals and non-metals provide the realistic performance evaluation, the entire process is time consuming and costly. Moreover, the process optimisation is done through trial error basis approach, which again imposes constraints on texture performance. Hence, it is essential to further develop a good correlation between experimental responses and theoretical models. Also influence of optical parameters such as absorptivity, reflectivity and focal distance also plays a crucial role in determining the optimised qualitative texture characteristics such as texture density, texture depth and aspect ratio, in situ investigation have to be reported. As pointed by Q Shang et al. [102], research on laser texturing of lightweight alloys of copper, aluminium must be further enhanced to tune them for contact applications thereby leading to lower energy consumption and improved material service life.

References 1. Erdo Lan, M., yktem, B., Kalaycıo Llu, H., Yavaf, S., Mukhopadhyay, P.K., Eken, K.y., Aykac, Y., Tazebay, U.H., Ilday, F.y.: Texturing of titanium (Ti6Al4V) medical implant surfaces with MHzrepetition-rate femtosecond and picosecond Yb-doped fiber lasers. Opt Express. 19, 10986–10996 (2011) 2. Ancona, A., Roser, F., Rademaker, K., Limpert, J., Nolte, S., Tünnermann, A.: High speed laser drilling of metals using a high repetition rate, high average power ultrafast fiber CPA system. Opt Express. 6(12), 8958–8968 (2008) 3. Yoshino, F., Shah, L., Fermann, M., Arai, A., Uehara, Y.: Micromachining with a high repetition rate femtosecond fiber laser. J. Laser Micro / Nanoeng. 3, 157–162 (2008) 4. Abdul, F., Tahira, M., Nur Aqidab, S.: An investigation of laser cutting quality of 22MnB5 ultra high strength steel using response surface methodology. Opt Laser Technol. 92, 142–149 (2017) 5. Zaied, M., Miraoui, I., Boujelbene, M., Bayraktar, E.: Analysis of heat affected zone obtained by CO2 laser cutting of low carbon steel (S235). AIP Conf Proc. 1569, (2013) 6. Bharatish, A., Narasimha Murthy, H.N., Anand, B., Madhusoodana, C.D., Praveena, G.S., Krishna, M.: Characterization of hole circularity and heat affected zone in pulsed CO2 laser drilling of alumina ceramics. Opt Laser Technol. 53, 22–32 (2012) 7. Wang, Y.: Crack separation mechanism applied in CO2 laser machining of thick Polycrystalline Cubic Nitride (PCBN) tool blanks. Graduate Theses and Dissertations. http://lib.dr.iastate.edu/etd/14696 (2015)

Lasers Manuf. Mater. Process. 8. Akhmetov, I.D., Zakirova, A.R., Sadykov, I.O.P.: Z.B.: the analysis and selection of methods and facilities for cutting of naturally-deficit materials, Conf. Series. Mater Sci Eng. 134, 012002 (2016) 9. Webster, P.J.L., Yu, J., Z, X., Leung, B.Y.C., Anderson, M.D., Yang, V.X.D., Fraser, J.M.: In situ 24kHz coherent imaging of morphology change in laser percussion drilling. Opt Lett. 35(5), 646–648 (2010) 10. Yilbas, B.S., Akhtar, S.S., Keles, O.: Laser cutting of small diameter hole in aluminium foam. Int J Adv Manuf Technol. 79(1-4), 101–111 (2015) 11. Anoop, S.: Laser Machining of Advanced Materials. CRC Press, London (2011) 12. Tanvir, A., M, K., Grambow, C., Anne-Marie, K.: Fabrication of micro/Nano structures on metals by femtosecond laser micromachining. Micromachines. 5, 1219–1253 (2014) 13. Sibbett, W., Lagatsky, A.A., Brown, C.T.A.: The development and application of femtosecond laser systems. Opt Express. 20, 6989–7001 (2012) 14. Brizmer, V., Kligerman, Y., Etsion, I.: A laser surface textured parallel thrust bearing. Tribol Trans. 46(3), 397–403 (2003) 15. Brizmer, V., Kligerman, Y.: A laser surface textured journal bearing. J Tribol. 134(3), 031702 (2012) 16. Yin, B., Li, X., Fu, Y., Yun, W.: Effect of laser textured dimples on the lubrication performance of cylinder liner in diesel engine. Lubr Sci. 24(7), 293–312 (2012) 17. Ryk, G., Etsion, I.: Testing piston rings with partial laser surface texturing for friction reduction. Wear. 261(7-8), 792–796 (2006) 18. Etsion, I., Sher, E.: Improving fuel efficiency with laser surface textured piston rings. Tribol Int. 42(4), 542–547 (2009) 19. Sudeep, U., Tandon, N., Pandey, R.K.: Effects of surface texturing on friction and vibration behaviors of sliding lubricated concentrated point contacts under linear reciprocating motion. Tribol Int. 62, 198–207 (2013) 20. Sudeep, U., Tandon, N., Pandey, R.K.: Tribological studies of lubricated laser-textured point contacts in rolling/sliding reciprocating motion with investigations of wettability and Nanohardness. Tribol T. 58(4), 625–634 (2015) 21. Chien-Yu, C., Chung-Jen, C., Bo-Hsiung, W., Wang-Long, L., Chih-Wei, C., Ping-Han, W., ChungWei, C.: Microstructure and lubricating property of ultra-fast laser pulse textured silicon carbide seals. Appl Phys A Mater Sci Process. 107(2), 345–350 (2012) 22. Zhou, M., Yu, J., Li, J., B, W., Zhang, W.: Wetting induced fluid spread on structured surfaces at microscale. Appl Surf Sci. 258(19), 7596–7600 (2012) 23. Correa, D.S., Almeida, J.M., Almeida, G.F., Cardoso, M.R., De Boni, L., Mendonca, C.R.: Ultrafast laser pulses for structuring materials at micro/Nano scale: from waveguides to Superhydrophobic surfaces. Photo-Dermatology. 4, 1–26 (2017) 24. Truong, S.L., Levi, G., Bozon-Verduraz, F., Petrovskaya, A.V., Simakin, A.V., Shafeev, G.A.: Generation of nanospikes via laser ablation of metals in liquid environment and their activity in surface-enhanced raman scattering of organic molecules. Appl Surf Sci. 254(4), 1236–1239 (2007) 25. Yang, J., Yang, Y., Zhao, B., Wang, Y., Zhu, X.: Femtosecond laser-induced surface structures to significantly improve the thermal emission of light from metals. Appl Phys B Lasers Opt. 106(2), 349– 355 (2012) 26. Carey, J.E., Crouch, C.H., Shen, M.Y., Mazur, E.: Visible and near-infrared responsivity of femtosecond-laser microstructured silicon photodiodes. Opt Lett. 30(14), 1773–1775 (2005) 27. Barmina, E.V., Barberoglou, M., Zorba, V., Simakin, A.V., Stratakis, E., Fotakis, C., Shafeev, G.A.: Laser control of the properties of nanostructures on ta and Ni under their ablation in liquids. J Optoelectron Adv Mater. 12, 495–499 (2010) 28. Neuenschwander, B., Jaeggi, B., Schmid, M., Hennig, G.: Surface structuring with ultra-short laser pulses: basics, limitations and needs for high throughput. Phys Procedia. 56, 1047–1058 (2014) 29. Izhak, E.: State of the art in laser surface texturing. J Tribol. 127(1), 248–253 (2005) 30. Zhuo, W., Quanzhong, Z., Chengwei, W.: Reduction of friction of metals using laser-induced periodic surface nanostructures. Micromachines. 6, 1606–1616 (2015) 31. Ibatan, T., Uddina, M.S., Chowdhury, M.A.K.: Recent development on surface texturing in enhancing tribological performance of bearing sliders. Surf Coat Technol. 272, 102–120 (2015) 32. Lawrence, R., Dowding, C., Waugh, D., Griffiths, J.B.: Laser surface engineering. In: Toyserkani, E., Rasti, N. (eds.) Ultrashort Pulsed Laser Surface Texturing. Woodhead Publishing Series, pp. 442–453 (2015) 33. Anisimov, S.I., Kapeliovich, B.L., Perel’man, T.L.: Electron emission from metal surfaces exposed to ultrashort laser pulses. Sov Phys JETP. 39, 375–377 (1974) 34. Chicbkov, B.N., Momma, C., Nolte, S., Alvensleben, F.Y., Tunnermann, A.: Femtosecond, picosecond and nanosecond laser ablation of solids. Appl Phys A Mater Sci Process. 63(2), 109–115 (1996)

Lasers Manuf. Mater. Process. 35. Nolte, S., Momma, C., Jacobs, H., Tunnermann, A., Chichkov, B.N., Wellegehausen, B., Welling, H.: Ablation of metals by ultrashort laser pulses. J Opt Soc Am B. 14(10), 2716–2722 (1997) 36. Malinauskas, M., Zukauskas, A., Hasegawa, S., Hayasaki, Y., Mizeikis, Y., Ričardas, B., Saulius, J.: Ultrafast laser processing of materials: from science to industry. Light Sci Appl. 5(8), e16133 (2016) 37. Smith, M.J., Yu-Ting, L., Meng-Ju, S., Mark, T.W., Eric, M., Silvija, G.: Pressure-induced phase transformations during femtosecond-laser doping of silicon. J Appl Phys. 5, 053524 (2011) 38. Sanjay, M., Vinod, Y.: Laser beam micro machining (LBMM) – a review. Opt Lasers Eng. 73, 89–122 (2015) 39. Van, D., Dunna, A., Thomas, J.W., Robert, W.K., Patrick, J.S., Emre, E., Colm, C., Jonathan, D.S.: Laser textured surface gradients. Appl Surf Sci. 371, 583–589 (2016) 40. Chen, J., Sabau, A.S., Jones, J.F., Hackett, A.C., Daniel, C., Warren, D.: Aluminum surface texturing by means of laser interference metallurgy. In: Hyland, M. (ed.) Light Metals 2015. Springer, Cham (2015) 41. Xin, J., Lingling, D.: Fabrication of complex micro/nanopatterns on semiconductors by the multi-beam interference of femtosecond laser. Phys Procedia. 56, 1059–1065 (2014) 42. Cunha, A., Omar, F.Z., Laurent, P., Ana, M.B.R., Almeida, A., Rui, V., Durrieu, M.C.: Human mesenchymal stem cell behaviour on femtosecond laser-textured Ti-6Al-4V surfaces. Nanomedicine. 10(5), 725–739 (2015) 43. Cunha, A., Oliveira, V., Serro, A.P., Omar, F.Z., Almeida, A., Durrieu, M.C., Vilar, R.: Ultrafast laser texturing of Ti - 6Al - 4V surfaces for biomedical applications, ICALEO, LIA Pub. 616, 910–918 (2013) 44. Cunha, A., Elie, A., Plawinski, M., Serrod, A.P., Botelho do Rego, A.M., Almeida, A., Urdaci, M.C., Durrieu, M.C., Vilar, R.: Femtosecond laser surface texturing of titanium as a method to reduce the adhesion of Staphylococcus aureus and biofilm formation. Appl Surf Sci. 360, 485–493 (2016) 45. Erdo Ŀan, M., ÿktem, B., Kalaycıo Ŀlu, H., Yavaf S., Mukhopadhyay, P.K., Eken K., ÿzgören, K., Aykaç, Y., Tazebay, U.H., Ilday F.Y. : Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers. Opt Express 19, 10986–10996 (2011) 46. Li, B.J., Li, H., Huang, L.J., Ren, N.F., Kong, X.: Femtosecond pulsed laser textured titanium surfaces with stable superhydrophilicity and superhydrophobicity. Appl Surf Sci. 389, 585–593 (2016) 47. Martinez-Calderon, M., Manso-Silvan, M., Rodriguez, A., Gomez-Aranzadi, M., Garcia-Ruiz, J.P., Olaizola, S.M., Martin-Palma, R.J.: Surface micro- and nano-texturing of stainless steel by femtosecond laser for the control of cell migration. Sci Rep. 6(1), 36296 (2016) 48. Ling, E.J.Y., Said, J., Brodusch, N., Gauvin, R., Servio, P., Kietzig, A.M.: Investigating and understanding the effects of multiple femtosecond laser scans on the surface topography of stainless steel 304 and titanium. Appl Surf Sci. 353, 512–521 (2015) 49. Stasic, J., Gakovic, B., Perrie, W., Watkins, K., Petrovic, S., Trtica, M.: Surface texturing of the carbon steel AISI 1045 using femtosecond laser in single pulse and scanning regime. Appl Surf Sci. 258(1), 290–296 (2011) 50. Dou, K., Knobbe, E.T., Parkhill, R.L., Wang, Y.: Surface texturing of aluminum alloy 2024-T73 via femto- and nanosecond pulse excimer laser irradiation. IEEE J Sel Top Quantum Electron. 6, 689–695 (2000) 51. Ahmmed, K.M.T., Ling, E.J.Y., Servio, P., Kietzig, A.M.: Introducing a new optimization tool for femtosecond laser-induced surface texturing on titanium, stainless steel, aluminum and copper. Opt Laser Eng. 66, 258–268 (2015) 52. Biswas, S., Karthikeyan, A., Anne-Marie, K.: Effect of repetition rate on femtosecond laser-induced homogenous microstructures. Materials 9, 10232016 53. He, X., Zhong, L., Wang, G., Liao, Y., Liu, Q.: Tribological behavior of femtosecond laser textured surfaces of 20CrNiMo/beryllium bronze tribo-pairs. Ind Lubr Tribol. 67(6), 630–638 (2015) 54. Gavrilov, A.I., Golovin, D.V., Emelyanenko, A.M., Zayarny, D.A., Ionin, A.A., Kudryashov, S.I., Makarov, S.V., Saltuganov, P.N., Boinovich, L.B.: Nano and microstructuring of materials surfaces using femtosecond laser pulses, bulletin of the Russian Academy of Sciences. Physics. 80, 358–361 (2016) 55. Raimbault, O., Benayoun, S., Anselme, K., Mauclair, C., Bourgade, T., Kietzig, A.M., Girard-Lauriault, P.L., Valette, S., Donnet, C.: The effects of femtosecond laser-textured Ti-6Al-4Von wettability and cell response. Mater Sci Eng C. 69, 311–320 (2016) 56. Semaltianos, N.G., Perrie, W., French, P., Sharp, M., Dearden, G., Watkins, K.G.: Femtosecond laser surface texturing of a nickel-based superalloy. Appl Surf Sci. 255(5), 2796–2802 (2008) 57. Jeong, Y.H., Sonc, I.B., Choe, H.C.: Formation of surface roughness on the Ti–35Nb–xZr alloy using femtosecond laser for biocompatibility. Procedia Eng. 10, 2393–2394 (2011)

Lasers Manuf. Mater. Process. 58. Jeong, Y.H., Choe, H.C., Brantley, W.A., Sohn, I.B.: Hydroxyapatite thin film coatings on nanotubeformed Ti–35Nb–10Zr alloys after femtosecond laser texturing. Surf Coat Technol. 217, 13–22 (2013) 59. Nayak, B.K., Gupta, M., Kolasinski, K.: Formation of nano-textured conical microstructures in titanium metal surface by femtosecond laser irradiation. Appl Phys A Mater Sci Process. 90, 399–402 (2008) 60. Craig, A. Z., Troy, P. A., Pengbo, Li, Michael, JL, Nick, R, Jeffery, ES, Benjamin, T, Dennis, R A: Superhydrophobic metallic surfaces functionalized via femtosecond laser surface processing for long term air film retention when submerged in liquid Proc of SPIE. 93510J-935101 (2015) 61. Bashir, S., Shahid Rafique, M., Nathala, C.S., Husinsky, W.: The formation of Nano dimensional structures on the surface of tin exposed to femtosecond laser pulses in the ambient environment of ethanol. Appl Surf Sci. 290, 53–58 (2014) 62. Barmina, E.V., Stratakis, E., Barberoglou, M., Stolyarov, V.N., Stolyarov, I.N., Fotakis, C., Shafeeva, G.A.: Laser-assisted nanostructuring of tungsten in liquid environment. Appl Surf Sci. 258(15), 5898– 5902 (2012) 63. Catalina, A., Adrian, D., Mihaela, F., Magdalena, U., Marian, Z.: Periodical structures induced by femtosecond laser on metals in air and liquid environments. Appl Surf Sci. 278, 347–351 (2013) 64. Wahab, J.A., Ghazali, M.J., Yusoff, W.M., Sajuri, Z.: Enhancing material performance through laser surface texturing: a review. Trans IMF. 94(4), 193–198 (2016) 65. Fatima, A., Whitehead, D.J., Mativenga, P.T.: Femtosecond laser surface structuring of carbide tooling for modifying contact phenomena. Proc IME B J Eng Manufact. 228(11), 1325–1337 (2014) 66. Lian, Y., Deng, J., Xing, Y., Lei, S., Yu, X.: Periodic and uniform nanogratings formed on cemented carbide by femtosecond laser scanning. Appl Surf Sci. 282, 518–524 (2013) 67. Barbosa, P.A., Bertolete, M., Samad, R.E., Junior, N.D.V., Machado, I.F.: Investigation of Femtosecond Laser Texturing in Cemented Carbide Cutting Tools. Proceedings of Lasers in Manufacturing Conference 2015. Munich doi: http://repositorio.ipen.br:8080/xmlui/handle/123456789/25483 68. Tshabalala, L.C., Ntuli, C.P., Fwamba, J.C., Popoola, P., Pityan, S.L.: Surface texturing of SiAlON ceramic by femtosecond pulsed laser. Proc Manufac. 7, 660–667 (2017) 69. Sciti, D., Trucchi, D.M., Bellucci, A., Orlando, S., Zoli, L., Sani, E.: Effect of surface texturing by femtosecond laser on tantalum carbide ceramics for solar receiver applications. Sol Energ Mat Sol C. 161, 1–6 (2017) 70. Xing, Y., Deng, J., Wang, X., Meng, R.: Effect of laser surface textures combined with multi-solid lubricant coatings on the tribological properties of Al2O3/TiC ceramic. Wear. 342, 1–343, 12 (2015) 71. Sugihara, T., Enomoto, T.: Performance of cutting tools with dimple textured surfaces: a comparative study of different texture patterns. Precis Eng. 49, 52–60 (2017) 72. Li, N., Chen, Y., Kong, D., Tan, S.: Experimental investigation with respect to the performance of deep submillimeter scaled textured tools in dry turning titanium alloy Ti-6Al-4V. Appl Surf Sci. 403, 187– 199 (2017) 73. Deng, J., Lian, Y., Wu, Z., Xing, Y.: Performance of femtosecond laser-textured cutting tools deposited with WS2 solid lubricant coatings. Surf Coat Technol. 222, 135–143 (2013) 74. Zhang, K., Deng, J., Meng, R., Gao, P., Yue, H.: Effect of nano-scale textures on cutting performance of WC/co-based Ti55Al45N coated tools in dry cutting. Int J Refract Met H. 51, 35–49 (2015) 75. Enomoto, T., Sugihara, T.: Improving anti-adhesive properties of cutting tool surfaces by nano−/microtextures. CIRP Ann Manuf Technol. 59(1), 597–600 (2010) 76. Bhaduri, D., Batal, A., Dimov, S.S., Zhang, Z., Dong, H., Fallqvist, M., Saoubid, R. M, Machadod, AR, Vilare, R, Rossib, W : On design and tribological behaviour of laser textured surfaces, Proc CIRP 60, 20–25 (2017) 77. See, T.L.: Laser surface texturing – fundamental study and applications. PhD thesis. In: University of Manchester (2015) 78. Wang, B., Wang, X., Zheng, H., Lam, Y.: Femtosecond laser-induced surface wettability modification of polystyrene surface. Sci China-Phys Mech Astron D. 59(12), 124211 (2016) 79. Kenji, G., Yuji, Y., Yusuke, F., Masato, T., Ooie, T., Abe, K., Kataoka, M.: Femtosecond laser direct fabrication of micro-grooved textures on a capillary flow immunoassay microchip for spatially-selected antibody immobilization. Sensor Actuator B. 239, 1275–1281 (2017) 80. Shashank, S., Shin, Y.C.: Superhydrophobic contoured surfaces created on metal and polymer using a femtosecond laser. Appl Surf Sci. 405, 465–475 (2017) 81. Fan, W., Qian, J., Baia, F., Li, Y., Wang, C., Zhao, Q.: A facile method to fabricate super amphiphobic polytetra fluoroethylene surface by femtosecond laser pulses. Chem Phys Lett. 644, 261–266 (2016) 82. Riveiro, A., Soto, R., Comesana, R., Boutinguiza, M., del Val, J., Quintero, F.: Laser surface modification of PEEK. Appl Surf Sci. 258(23), 9437–9442 (2012)

Lasers Manuf. Mater. Process. 83. Hammouti, S., Pascale-Hamri, N., Faure, B., Beaugiraud, M., Guibert, C., Mauclair, S., Benayoun, S., Valette, S.: Wear rate control of peek surfaces modified by femtosecond laser. Appl Surf Sci. 357, 1541– 1551 (2015) 84. Marcelo, G., Martinho, J.M.G., Farinha, J.P.S.: Polymer-coated nanoparticles by adsorption of hydrophobically modified poly (N,N-dimethylacrylamide). J Phys Chem B. 117(12), 3416–3427 (2013) 85. Rose, S., Prevoteau, A., Elziere, P., Hourdet, D., Marcellan, A., Leibler, L.: Nanoparticle solutions as adhesives for gels and biological tissues. Nature. 505(7483), 382–385 (2014) 86. Tran, N.T.D., Truong, N.P., Gu, W., Jia, Z., Cooper, M.A., Monteiro, M.J.: Timed-release polymer nanoparticles. Biomacromolecules. 14(2), 495–502 (2013) 87. MacNeill, C.M., Graham, E.G., Levi-Polyachenko, N.H.: Soft template synthesis of donor–acceptor conjugated polymer nanoparticles: structural effects, stability, and photothermal studies. J Polym Sci A Polym Chem. 52(11), 1622–1632 (2014) 88. Jackson, A.W., Fulton, D.A.: Making polymeric nanoparticles stimuli-responsive with dynamic covalent bonds. Polym Chem. 4(1), 31–45 (2013) 89. Martinez-Tong, D.E., Sanz, M., Ezquerra, T.A., Nogales, A., Marco, J.F., Castillejo, M., Rebollar, E.: Formation of polymer nanoparticles by UV pulsed laser ablation of poly (bisphenol a carbonate) in liquid environment. Appl Surf Sci. 418, 522–529 (2017) 90. Chang, T.C., Malian, P.A.: Excimer pulsed laser ablation of polymers in air and liquids for micromachining applications. J Manuf Process. 18, 1–18,17 (1999) 91. Wang, H., Kongsuwan, P., Satoh, G., Lawrence Yao, Y.: E femtosecond laser induced surface texturing crystallization of a-Si:H thin film. ASME 2010 international manufacturing science and Eng Conf. 2, 255–264 (2010). https://doi.org/10.1115/MSEC2010-34271 92. Smith, M.J., Yu-Ting Lin, M.-J.S., Winkler, M.T., Mazur, E., Gradeccak, S.: Pressure-induced phase transformations during femtosecond-laser doping of silicon. J Appl Phys. 110(5), 053524 (2011) 93. Oliveira, V., Sharma, S.P., de Moura, M.F.S.F., Moreira, R.D.F., Vilar, R.: Surface treatment of CFRP composites using femtosecond laser radiation. Opt laser Eng. 94, 37–43 (2017) 94. Koch, J., korte, F., bauer, T., fallnich, C., Ostendorf, A., Chichkov, B.N.: Nanotexturing of gold films by femtosecond laser-induced melt dynamics. Appl Phys A Mater Sci Process. 81(2), 325–328 (2005) 95. Tagawa, N., Takada, M., Mori, A., Sawada, H., Kawahara, K.: Development of contact sliders with nanotextures by femtosecond laser processing. Tribo Lett. 24(2), 143–149 (2006) 96. Zha, J., Ali, S.S., Peyroux, J., Batisse, N., Claves, D., Dubois, M., Alexander, P.K., Monier, G., Darmanin, T., Guittard, F., Alekseiko, L.N.: Superhydrophobicity of polymer films via fluorine atoms covalent attachment and surface nano-texturing. J Fluor Chem. 200, 123–132 (2017) 97. Nava, G., Osellame, R., Ramponi, R., Vishunubhatla, K.: Femtosecond laser micro-texturing of silicon using high repetition rate pulses for photovoltaic applications. International Conference on Fibre Optics and Photonics. (2012). https://doi.org/10.1364/PHOTONICS.2012.T3B.4 98. Yang, H., Zhou, L., He, H., Qian, J., Hao, J., Zhu, H.: Textures induced by a femtosecond laser on silicon surfaces under various environments. J Russ Laser Res. 33(4), 349–355 (2012) 99. Albu, C., Dinescu, A., Filipescu, M., Ulmeanu, M., Zamfirescu, M.: Periodical structures induced by femtosecond laser on metals in air and liquid environments. Appl Surf Sci. 278, 347–351 (2013) 100. Radu, C., Simion, S., Zamfirescu, M., Ulmeanu, M., Enculescu, M., Radoiu, M.: Silicon structuring by etching with liquid chlorine and fluorine precursors using femtosecond laser pulses. J Appl Phys. 110(3), 034901 (2011) 101. Wang, Q., Zhou, W.: Direct fabrication of cone array microstructure on monocrystalline silicon surface by femtosecond laser texturing. Opt Mater. 72, 508–512 (2017) 102. Shang, Q., Yu, A., Wu, J., Shi, C., Niu, W.: Influence of heat affected zone on tribological properties of CuSn6 bronze laser dimple textured surface. Tribol Int. 105, 158–165 (2017)