polymers Article
A Facile Approach for Fabricating Microstructured Surface Based on Etched Template by Inkjet Printing Technology Jiazhen Sun *, Chenghu Yun, Bo Cui, Pingping Li, Guangping Liu, Xin Wang and Fuqiang Chu Key Laboratory of Pulp, Paper, Printing & Packaging of China National Light Industry, Key Laboratory of Printing & Packaging Materials and Technology of Shandong Province, School of Light Industry and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China;
[email protected] (C.Y.);
[email protected] (B.C.);
[email protected] (P.L.);
[email protected] (G.L.);
[email protected] (X.W.);
[email protected] (F.C.) * Correspondence:
[email protected]; Tel.: +86-531-8963-1787 Received: 18 September 2018; Accepted: 29 October 2018; Published: 31 October 2018
Abstract: Microstructures are playing an important role in manufacturing functional devices, due to their unique properties, such as wettability or flexibility. Recently, various microstructured surfaces have been fabricated to realize functional applications. To achieve the applications, photolithography or printing technology is utilized to produce the microstructures. However, these methods require preparing templates or masks, which are usually complex and expensive. Herein, a facile approach for fabricating microstructured surfaces was studied based on etched template by inkjet printing technology. Precured polydimethylsiloxane substrate was etched by inkjet printing water-soluble polyacrylic acid solution. Then, the polydimethylsiloxane substrate was cured and rinsed, which could be directly used as template for fabricating microstructured surfaces. Surfaces with raised dots, lines, and squares, were facilely obtained using the etched templates by inkjet printing technology. Furthermore, controllable anisotropic wettability was exhibited on the raised line microstructured surface. This work provides a flexible and scalable way to fabricate various microstructured surfaces. It would bring about excellent performance, which could find numerous applications in optoelectronic devices, biological chips, microreactors, wearable products, and related fields. Keywords: inkjet printing; etched template; microstructured surface; anisotropic wettability
1. Introduction Microstructures are playing an important role in manufacturing functional devices, due to their unique properties, such as wettability or flexibility [1,2]. Recently, various microstructured surfaces have been fabricated to realize functional applications in manipulating droplets, wearable devices, and energy conversion [3–5]. The microstructured surfaces are commonly prepared by some methods for constructing various functional materials on the surfaces, which could be used to realize the applications [6,7]. Previously, there has been much effort to fabricate microstructured surfaces for some special functionality, including laser etching, photomask template processing, microcontact printing, and so on [8–11]. Maeng et al. created a 3D microcavity array via a reactive ion etching (RIE) process, which contributed to the increment of the area capacitance [5]. Lee et al. used a double photolithography method to obtain the mogul-patterned substrate, which provided more possibilities for device flexibility [12]. Liu et al. obtained a separate metallic network structure by depositing metal material on a template by using laser-direct writing patterning techniques [13]. However, the abovementioned methods require elaborately fabricating templates or expensive vacuum deposited
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masks that restrict practical applications. Therefore, it is highly desirable to conceive a simple and effective route to fabricate substrates with various microstructures. As a solution processing method, printing technology is widely used to fabricate various functional patterns [14]. Especially, inkjet printing technology has been proved to be a versatile patterning technique because of its direct-writing and mask-free properties. With the high resolution, cost saving, and efficient use of materials [15–19], inkjet printing technology has aroused wide attention as a simple and efficient way for patterning functional materials. Various functional materials are deposited by inkjet printing to fabricate transistor circuits, light-emitting polymer displays, solar cells, sensor arrays, stretchable heater, optical devices, and other devices [20–27]. Meanwhile, viscoelastic substrate and sacrificial polymer etching could produce various micro/nanostructures for special applications. Szilasi et al. conducted an in-depth study of the selective etching of polydimethylsiloxane (PDMS) using potassium hydroxide and sodium hydroxide [28]. Liu et al. used soft lithography to obtain PDMS with a rectangular channel as the top layer of the device [29]. Wang et al. deposited polymethyl methacrylate (PMMA) onto a silica substrate as a sacrificial mask to deposit a metal film [30]. Melzer et al. used polyacrylic acid (PAA) as a sacrificial layer to transfer the magnetic sensor directly to the elastomer [31]. Agarwal et al. performed large-scale nanoimprinting based on the different solubility of the sacrificial PAA layer between monovalent and divalent cations [32]. In this study, a facile approach for fabricating microstructured surfaces was studied based on etched template by inkjet printing technology. Precured polydimethylsiloxane substrate was etched by inkjet printing water-soluble polyacrylic acid solution. Then, the polydimethylsiloxane (PDMS) substrate was cured and rinsed, which could be directly used as a template for fabricating microstructured surfaces. Surfaces with raised dots, lines, and squares, were facilely obtained using the etched templates by inkjet printing technology. Furthermore, controllable anisotropic wettability was exhibited on the raised line microstructured surface. This work provides a flexible and scalable way to fabricate various microstructured surfaces. It would bring about excellent performance, which could find numerous applications in optoelectronic devices, biological chips, microreactors, wearable products, and related fields. 2. Materials and Methods 2.1. Materials PDMS (precursor and curing agent): (Sylgard 184, Dow Corning, Midland, MI, USA). Polyethylene glycol terephthalate (PET): (Beijing Daxiang Plastic Co., Ltd., Beijing, China). Ethanol: (Beijing Chemical Co., Ltd., Beijing, China). Polyacrylic acid (PAA, Mw = 1800, Sigma-Aldrich, Saint Louis, MO, USA). Polyvinyl alcohol (PVA, 1788, Sigma-Aldrich, Saint Louis, MO, USA). Deionized water (generated by Milli-Q water purification system, Beijing, China). 2.2. Preparation of Water-Soluble Polymer Ink Polyacrylic acid (PAA, MW = 1800, Sigma-Aldrich) dissolved in water/ethanol mixed solvent (with volume ratio 20:80) was used as the sacrificial ink. The concentration of the ink was kept as 16 wt %. 2.3. Preparation of Inkjet Printing Substrate PDMS base was mixed with a curing agent in the proportion of 15:1, by weight, to make PDMS precursor (Sylgard 184). The precursor was put into a centrifuge to remove air bubbles (1000 rpm, 2 min), then it was put onto a PET-supporting layer by spin-coating at 800 rpm for 20 s. The height of the liquid PDMS film was about 150 µm. As the too-thin film would be affected by the PET supporting layer, and the too-thick film would induce an unstable thermoresponsibility, the thickness of PDMS film was chosen as 150 µm in this experiment. Subsequently, the PDMS precursor with reducing agent was precured in a 70 ◦ C oven for a given time, and used as the inkjet printing liquid substrate [33,34].
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2.4. Inkjet Printing Water-Soluble Polymer Ink The inkjet printing process was performed via Dimatix Materials Printer (FUJIFILM DMP-2800 series, Tokyo, Japan) with a 25 µm nozzle and 10 µm inkjet droplet precise distance controlled with Dimatix Drop Manager Software. The diameter of inkjet droplet was about 25 µm, with the 25 µm nozzle. In this work, the factor influencing the diameter of inkjet droplet was just considered with the pushing stage, that the diameter of droplet was confined by the diameter of nozzle. The environmental temperature of inkjet printing was 25 ◦ C. The humidity of the environment was 65%. A single nozzle was used during the inkjet printing process. Inkjet printing frequency was 5.0 kHz. A customized waveform was utilized in inkjet printing with piezoelectric maximum 30 V, and pulse width 8.5 µs. 2.5. Fabrication of Inkjet Printed Template Then, the inkjet-printed substrates were heated at 70 ◦ C for another 1 h to completely solidify the PDMS precursor. After rinsing with water, water-soluble polymer could be removed from the surface of substrates. The inkjet-printed substrates could be used as templates. When replicating materials were spin-coated on the inkjet-printed substrates and, subsequently, uncovered slowly, microstructured patterns of these materials could be immediately constructed. The replicating materials should satisfy the condition that the materials could transfer onto a film with evaporating or curing, such as PDMS or PVA. Therefore, the microstructured surfaces were facilely fabricated. 2.6. Characterization Structures of inkjet-printed patterns were investigated by SEM (JSM-7500, Tokyo, Japan), with a scanning voltage of 5 kV. Optical micrographs were acquired by optical microscope (Olympus MX40, Tokyo, Japan). Contact angles of the patterned substrates were measured using a contact angle system (Dataphysics OCA20, Filderstadt, Germany) at ambient temperature. The height profiles of the patterned surface were determined in a surface profiler (Kosaka ET4000, Tokyo, Japan). 3. Results and Discussions 3.1. Fabricating Microstructured Surfaces Based on Etched Template by Inkjet Printing Technology Figure 1 demonstrates the template fabricating and microstructure patterning processes. Firstly, PDMS substrates are etched into templates by inkjet printing technology. The fabricating process is that PDMS precursor is spin-coated onto a supporting layer, and precured into viscoelastic state. Water polyacrylic acid (PAA) ink is inkjet-printed onto the viscoelastic surface to form semi-wrapped structures. The inkjet droplet could imprint the viscoelastic precured PDMS substrate and generate a semi-wrapped deposit. When the precured PDMS liquid film is connected to the evaporating PAA droplet, the depositing resolution of inkjet droplets would be improved with the viscoelastic pressure of substrate. The existing position of deposited structure is influenced by the fluidity and viscoelasticity. If the precured PDMS liquid film has a high fluidity, the water-soluble deposits would exist in the PDMS substrate. If the precured PDMS liquid film has a high viscoelasticity, the water-soluble deposits would exist on the PDMS substrate. Accordingly, water-soluble deposits with semi-wrapped structure are generated on the PDMS surface with a proper cure temperature and time. After solidification of the substrate and rinsing the deposited PAA, the etched substrate is produced as the template. When various materials are spin-coated on the template, the etched template would be replicated onto the surface of various materials. Then, the materials are uncovered slowly from the templates, and the surfaces with functional microstructures would be facilely fabricated. Therefore, patterned microstructures of these materials could be immediately constructed based on etched templates by inkjet printing technology.
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Figure 1. Scheme of fabricating microstructured surface based on etched templates by inkjet Figure 1. Scheme of of fabricating fabricating microstructured microstructured surface surface based based on on etched templates by inkjet printing 1.technology. Scheme printing technology. technology.
Figure 2 shows the morphologies of etched template with line pattern and the fabricated Figure the morphologies of with line pattern and fabricated microstructured surface raised line, which weretemplate characterized SEM. The etched resolution is Figure 22 shows shows thewith morphologies of etched etched template with by line pattern and the the fabricated microstructured surface with raised line, which were characterized by SEM. The etched resolution 10 μm, and the resolution of replicated is also 10 μm. this The process, theresolution PDMS was microstructured surface with raised line,microstructure which were characterized byInSEM. etched is is µm, and the resolution ofmicrostructured replicated microstructure is also 10PDMS µm. In process, the PDMS also used asthethe materialofofreplicated surface, because is this commonly as 1010 μm, and resolution microstructure is also 10 μm. In this process, the applied PDMS was was used as the material microstructured surface,because becausePDMS PDMS commonly applied as various surfaces with its transparency, flexibility, and isis good biocompatibility. also also usedfunctional as the material of of microstructured surface, commonly applied as various functional surfaces with its transparency, flexibility, and good biocompatibility. Meanwhile, Meanwhile, the morphologies of microstructured surfaces with raised and squares, various functional surfaces with its transparency, flexibility, and dots, goodlines, biocompatibility. the morphologies of microstructured withsurfaces raised dots, and squares, which were which were the fabricated based on the surfaces etched templates (Figures S1 and S2) by inkjet printing Meanwhile, morphologies of microstructured with lines, raised dots, lines, and squares, fabricated based on the etched templates (Figures S1 and S2) by inkjet printing technology, were technology, characterized (Figure templates 3). The raised microstructures were from which werewere fabricated based by on SEM the etched (Figures S1 and S2) by replicated inkjet printing characterized by SEM (Figure The 3).byThe raised microstructures replicated from multilayer etched multilayer templates. diameters were with the multilayer etched templates. technology,etched were characterized SEM (Figure 3). improved The raisedwere microstructures were replicated from templates. The diameters were improved with the multilayer etched templates. The smooth edge The smooth edge of the template, after etching, could be presented with the high magnification multilayer etched templates. The diameters were improved with the multilayer etched templates. of thesmooth template, after could be presented with the high magnification images ofwith raised dots images of raised dots (Figure S3). The results show that microstructured surfaces raised The edge of etching, the template, after etching, could bethe presented with the high magnification (Figure S3). Thesquares, results show the surfaces with raised dots, lines, and squares, dots, lines, and couldthat be achieved with a large scale and high resolution, using the images of raised dots (Figure S3).facilely Themicrostructured results show that the microstructured surfaces with raised could be facilely achieved with a large scale and high resolution, using the etched templates by inkjet etched templates by inkjet technology. Structuring of complicated designs could be dots, lines, and squares, couldprinting be facilely achieved with a large scale and high resolution, using the printing technology. Structuring of complicated designs could be fabricated by combining thecould different fabricated by combining the different inkjet printing templates. One gradient microstructure with etched templates by inkjet printing technology. Structuring of complicated designs be inkjet printing templates. Onedifferent gradientinkjet microstructure with two types of raised line (Figure were fabricated two types of line were fabricated basedprinting on two types of etched template S4).with The fabricated byraised combining the templates. One line gradient microstructure based onoftwo types of etched (Figure S4).types The method of line producing template inkjet method producing template bytemplate inkjetbased printing technology an template efficient way to by produce two types of raised line were line fabricated on two ofprovides etched (Figure S4). The printing technology provides an efficient way to produce microstructured surfaces. microstructured surfaces. method of producing template by inkjet printing technology provides an efficient way to produce microstructured surfaces.
Morphologies of of the the etched etched template template and microstructured microstructured surface, surface, based on the etched Figure 2. Morphologies morphology template. Cross-section of the etched (b) Cross-section morphology of the Figure 2. (a) Morphologies ofmorphology the etched template and template. microstructured surface, based on the etched based on the etched template. (c) Top morphology replicated replicated microstructure based on the etched template. (c) Top view morphology of the template. (a) Cross-section morphology of the etched template. (b) Cross-section morphology of the microstructure based on the etched template. replicated microstructure based on template. the etched template. (c) Top view morphology of the replicated
microstructure based on the etched template.
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Figure 3. Morphologies of fabricated microstructured surfaces based on the etched template. (a) The 3. Morphologies of fabricated microstructured surfaces based on on the the etched etched template. template. (a) The Figure 3. microstructured surface with raised dot. (b) The microstructured surface with raised line. (c) The raised dot. dot. (b) The microstructured microstructured surface surface with with raised raised line. line. (c) The The microstructured surface with raised microstructured surface with raised square. Scale bar: 200 μm. microstructured surface surface with with raised raised square. square. Scale Scale bar: bar: 200 200 µm. μm. microstructured
3.2. Controllable Fabrication of Microstructured Surfaces Based on Etched Template by Inkjet Printing 3.2. 3.2. Controllable Controllable Fabrication Fabrication of of Microstructured Microstructured Surfaces Surfaces Based Based on on Etched Etched Template Templateby byInkjet Inkjet Printing Printing Technology Technology Technology Themorphologies morphologiesofofthe theetched etchedtemplates templatesare are determined determinedby by the the interactions interactions between betweenthe the The The morphologies of the etched templates are determined by the interactions between the inkjet-printed droplets and the viscoelastic PDMS substrates, which could be adjusted by inkjet inkjet-printed droplets and the viscoelastic PDMS substrates, which could be adjusted by inkjet inkjet-printed droplets and the viscoelastic PDMS substrates, which could be adjusted by inkjet printinglayers. layers.As Asshown shownininFigure Figure4,4,the thetemplates templateswith withdifferent differentprinting printinglayers layerswere werefabricated, fabricated, printing printing layers. As shown in Figure 4, the templates with different printing layers were fabricated, andthe themicrostructures microstructureswith withdifferent differentmorphologies morphologieswere werealso alsofabricated fabricatedbased basedon onthe thechanged changed and and the microstructures with different morphologies were also fabricated based on the changed templates.The The diameter of etched template be adjusted with the printing inkjet printing layers, templates. diameter of etched template couldcould be adjusted with the inkjet layers, which templates. The diameter of etched template could be adjusted with the inkjet printing layers, which whichbe could be to used to obtain differently replicated microstructured surfaces. showthe thegroove groove could used obtain differently replicated microstructured surfaces. To To show could be used to obtain differently replicated microstructured surfaces. To show the groove structureclearly, clearly,thethe cross-morphologies of templates the templates and microstructures were in shown structure cross-morphologies of the and microstructures were shown Figurein structure clearly, the cross-morphologies of the templates and microstructures were shown in Figure 5. Profiles the raised line structures characterized profilometer (FigureS5). S5). 5.Figure Profiles of the of raised line structures havehave beenbeen characterized by by profilometer (Figure 5. Profiles of the raised line structures have been characterized by profilometer (Figure S5). Meanwhile,the themicrostructured microstructuredsurfaces surfaceswith withdifferent differentmaterials materialswere werealso alsorealized. realized.Figure Figure66shows shows Meanwhile, Meanwhile, the microstructured surfaces with different materials were also realized. Figure 6 shows thatthe themicrostructured microstructuredsurfaces surfacesofofpolyvinyl polyvinylalcohol alcohol(PVA) (PVA)could couldalso alsobe befabricated fabricatedbased basedon onthe the that that the microstructured surfaces of polyvinyl alcohol (PVA) could also be fabricated based on the changingtemplates. templates. changing changing templates.
Figure 4. Morphologies of etchedline linetemplates templates and microstructured surface raised line Figure and thethe microstructured surface withwith raised line based Figure 4. 4. Morphologies Morphologiesofofetched etched line templates and the microstructured surface with raised line based on multilayer inkjet-printed microtemplates. (a) The etched templates with different inkjet on multilayer inkjet-printed microtemplates. (a) The etched templates with different inkjet printing based on multilayer inkjet-printed microtemplates. (a) The etched templates with different inkjet printing (1, 3,from 5 layers from left(b) to right). (b) Themicrostructures replicated microstructures different layers (1,layers 3, 5 layers left to right). replicated with differentwith inkjet printing printing layers (1, 3, 5 layers from left toThe right). (b) The replicated microstructures with different inkjet printing layers (1, 3, 5 layers from left to right). layers (1, 3, 5 layers from left to right). inkjet printing layers (1, 3, 5 layers from left to right).
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Figure Figure 5. 5. Cross-section Cross-section morphologies morphologies of of etched etched line line templates templates and and the the microstructured microstructured surface surface with with raised line based on the etched templates. (a) The etched templates with different inkjet printing raised line linebased basedon onthe the etched templates. (a) The etched templates with different inkjet printing etched templates. (a) The etched templates with different inkjet printing layers layers left to right). (b) replicated layers (1, 3, 3, 5from 5 layers layers from left(b) to The right). (b) The Themicrostructures replicated microstructures microstructures with different inkjet (1, 3, 5 (1, layers left from to right). replicated with differentwith inkjetdifferent printing inkjet layers printing layers (1, 55 layers from printing layers (1, 3, 3, layers from left left to to right). right). (1, 3, 5 layers from left to right).
Figure Figure 6. 6. Morphologies Morphologies of of fabricated line line microstructured surfaces surfaces of of polyvinyl polyvinyl alcohol alcohol (PVA) based Figure 6. Morphologies of fabricated fabricated line microstructured microstructured surfaces of polyvinyl alcohol (PVA) (PVA) based based on 3, layers from left to right). on etched etched line line templates templates with with different different inkjet inkjet printing printing layers layers (1, (1, 3, 3, 555 layers layers from from left left to to right). right). on etched line templates with different inkjet printing layers (1,
3.3. Anisotropic Wetting Wetting Behavior Behavior 3.3. 3.3. Anisotropic Anisotropic Wetting Behavior on on Fabricated Fabricated Microstructured Microstructured Surfaces Surfaces Furthermore, the anisotropic anisotropic wetting wetting behavior behavior of of droplet was exhibited on the microstructured Furthermore, Furthermore, the the anisotropic wetting behavior of droplet droplet was was exhibited exhibited on on the the microstructured microstructured surface with raised raised lines. lines. The Themicrostructured microstructuredsurface surfacewith with raised raised lines lines could could be be facilely facilely obtained surface surface with with raised lines. The microstructured surface with raised lines could be facilely obtained obtained based on the above method, which would present the advantage of the approach fabricating based on the above method, which would present the advantage of the approach for fabricating based on the above method, which would present the advantage of the approach for fabricating microstructured surface based based on etched template Then, wetting microstructured microstructured surface surface based on on etched etched template template by by inkjet inkjet printing printing technology. technology. Then, Then, the the wetting wetting behaviors were characterized on the microstructured surfaces. As shown behaviors of water droplets were characterized on the microstructured surfaces. As behaviors of ofwater waterdroplets droplets were characterized on fabricated the fabricated fabricated microstructured surfaces. As ◦ on the unprocessed in Figure 7, the static wetting contact angle of a 5 µL water droplet was about 107.2 shown shown in in Figure Figure 7, 7, the the static static wetting wetting contact contact angle angle of of aa 55 μL μL water water droplet droplet was was about about 107.2° 107.2° on on the the PDMS surface. When the water droplet was residing on the fabricated microstructured surface with unprocessed PDMS surface. When the droplet residing on fabricated unprocessed PDMS surface. When the water water droplet was was residing on the the fabricated microstructured microstructured raised static wetting contact angles with different directions were investigated. The wetting surface with raised line, the wetting contact angles different directions were surfaceline, withthe raised line, the static static wetting contact angles with with different directions were investigated. investigated. behavior on the microstructured surface with raised line was studied with 60, 100, and 140100, µm and line The The wetting wetting behavior behavior on on the the microstructured microstructured surface surface with with raised raised line line was was studied studied with with 60, 60, 100, and spacing, It was found thatIt wetting behavior of wetting droplet the microstructured surface 140 line respectively. was found that behavior of 140 μm μm respectively. line spacing, spacing, respectively. Itthe was found that the the wettingon behavior of droplet droplet on on the the appeared as a large difference in the parallel direction and vertical direction in Figure 8. Meanwhile, microstructured surface appeared as a large difference in the parallel direction and vertical direction microstructured surface appeared as a large difference in the parallel direction and vertical direction the wetting8. of droplet on the microstructured surface also appeared as a large difference in Meanwhile, the behavior on microstructured surface also in Figure Figure 8.behavior Meanwhile, the wetting wetting behavior of of droplet droplet on the the microstructured surface with also different When the micrometer scale PDMS is treated with nanometerscale scale PDMS structure, appeared as with line spacing. When the micrometer appearedline as aspacing. a large large difference difference with different different line spacing. When thethe micrometer scale PDMS is is the hierarchical structure would exhibit some special wetting behavior of superamphiphobic or sliding treated treated with with the the nanometer nanometer scale scale structure, structure, the the hierarchical hierarchical structure structure would would exhibit exhibit some some special special wettability. Therefore, a flexible and speedy way to wettability. fabricate anisotropic surface was realized based on wetting of or Therefore, aa flexible and way wetting behavior behavior of superamphiphobic superamphiphobic or sliding sliding wettability. Therefore, flexible and speedy speedy way the etched template by inkjet printing technology. to fabricate anisotropic surface was realized based on the etched template by inkjet printing to fabricate anisotropic surface was realized based on the etched template by inkjet printing technology. technology.
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Figure 7. Wetting behavior of a 5 μL water droplet on a flat PDMS surface with static wetting contact Figure 7. Wetting Wetting behavior of a 5 μL µL water droplet on a flat PDMS surface with static wetting contact contact angle about 107.2°. angle about 107.2°. 107.2◦ .
Figure Figure 8. 8. Wetting Wetting behavior behaviorof of droplet droplet on on the the microstructured microstructured surface surface with with raised raised line line in in parallel parallel Figure 8. Wetting behavior of droplet on the microstructured surface with raised line in parallel direction and vertical direction with 60, 100, and 140 μm line spacing. direction and vertical direction µm direction and vertical direction with 60, 100, and 140 μm line spacing.
4. Conclusions Conclusions 4. 4. Conclusions In this this study, study, microstructured microstructured surfaces surfaces were were fabricated fabricated based based on on etched etched template template by by inkjet inkjet In In this study, microstructured surfaces were fabricated based oninkjet etched template by inkjet printing technology. Water-soluble polyacrylic acid solution was used as printing ink, and printing technology. Water-soluble polyacrylic acid solution was used as inkjet printing ink, then and printing technology. Water-soluble polyacrylic acid solution was used as inkjet printing After ink, and precured polydimethylsiloxane substrate was was etched by the printing technology. the then precured polydimethylsiloxane substrate etched by inkjet the inkjet printing technology. After then precured polydimethylsiloxane substrate was etched by the inkjet printing technology. After polydimethylsiloxane (PDMS) substrate was was cured and rinsed, the etched surface couldcould directly serve the polydimethylsiloxane (PDMS) substrate cured and rinsed, the etched surface directly the polydimethylsiloxane (PDMS)process substrate was curedmicrostructured and rinsed, the etched surface couldbased directly as template. Then, the fabricating of functional surface was studied on serve as template. Then, the fabricating process of functional microstructured surface was studied serve as template. Then, the fabricating process of functional microstructured surface was studied the etched template by inkjet printing technology. Surfaces with raised dots, lines, and squares based on the etched template by inkjet printing technology. Surfaces with raised dots, lines, and based on the etched template the by inkjet technology. with raised dots, lines, and were facilely etchedprinting templates inkjetSurfaces printing technology. squares were obtained facilely using obtained using the etched by templates by inkjet printing Furthermore, technology. squares were facilely obtained using the etched templates by inkjet printing technology. the microstructured surface with raised lines could be lines facilely obtained basedobtained on the above Furthermore, the microstructured surface with raised could be facilely basedmethod, on the Furthermore, the microstructured surface with raised lines could be facilely obtained based on the which method, would present the advantage of the approach microstructured surface based above which would present the advantage offor thefabricating approach for fabricating microstructured above method, which would present the advantage of the approach for fabricating microstructured on etched template by inkjet printingby technology. The controllable wetting behavior of surface based on etched template inkjet printing technology.anisotropic The controllable anisotropic surface based on etched template by inkjet printing technology. The controllable anisotropic droplets was exhibited on the processing surface with the microstructure of the raised line. A simple wetting behavior of droplets was exhibited on the processing surface with the microstructure of the wetting behavior of droplets was fabrication exhibited on processing surface with the microstructure of the methodline. wasAdeveloped for rapid of the functional surfaces. It is flexible and speedy way raised simple method was developed for rapid fabrication ofafunctional surfaces. It is to a raised line. A simple method was developed for rapid fabrication of functional surfaces. It is a fabricate functional microstructured surface based on the etched template by inkjet printing technology. flexible and speedy way to fabricate functional microstructured surface based on the etched flexible and speedy way to fabricate functional microstructured surface based on etched These microstructured surfaces would present performances, which could findthe numerous template by inkjet printing technology. Theseexcellent microstructured surfaces would present excellent template by in inkjet printing technology. These microstructured surfacesand would present excellent applications optoelectronic devices, lab-on-chip devices, microreactors, related fields. performances, which could find numerous applications in optoelectronic devices, lab-on-chip performances, which could find numerous applications in optoelectronic devices, lab-on-chip devices, microreactors, and related fields. Supplementary Materials: The following are available online at http://www.mdpi.com/2073-4360/10/11/ devices, microreactors, and related fields. 1209/s1, Figure S1: SEM image of etched dot template for fabricating microstructured surfaces with raised dots, Supplementary Materials: The following are available online at www.mdpi.com/xxx/s1, Figure S1: SEM image Supplementary Materials: The following are available online at www.mdpi.com/xxx/s1, Figure S1: SEM image of etched dot template for fabricating microstructured surfaces with raised dots, Figure S2: SEM image of of etched dot template for fabricating microstructured surfaces with raised dots, Figure S2: SEM image of
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Figure S2: SEM image of etched square template for fabricating microstructured surfaces with raised squares, Figure S3: Optical image of the high magnification images of raised dot microstructured surface, fabricated based on the etched template, Figure S4: Structuring of complicated designs with one gradient microstructure fabricated based on two types of the etched line template, Figure S5: Profiles of the raised line microstructured surface fabricated based on the etched template. Author Contributions: X.W. and F.C. conceived and designed the experiment; C.Y. and B.C. reviewed the manuscript technically and grammatically; P.L. and G.L. conducted the experiment and analyzed the data; J.S. performed the experiments and wrote the manuscript. Funding: We gratefully acknowledge financial support from the National Natural Science Foundation of China (No. 21703110). Conflicts of Interest: The authors declare no conflict of interest.
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