technologies Article
Electronically Re-Configurable, Non-Volatile, Nano-Ionics-Based RF-Switch on Paper Substrate for Chipless RFID Applications Jayakrishnan Methapettyparambu Purushothama 1, * and Etienne Perret 1,3 1 2 3
*
ID
, Arnaud Vena 2 , Brice Sorli 2
Grenoble INP, LCIS, Université Grenoble Alpes, 26902 Valence, France;
[email protected] Institut d’Electronique et Systèmes (IES), Université de Montpellier, 34095 Montpellier, France;
[email protected] (A.V.);
[email protected] (B.S.) Institut Universitaire de France, 75005 Paris, France Correspondence:
[email protected]; Tel.: +33-4-67149537
Received: 11 May 2018; Accepted: 25 June 2018; Published: 27 June 2018
Abstract: This article reports the first results of a Nafion® -based, solid state, non-volatile, electronically reconfigurable Radio Frequency (RF)-switch integrated to a co-planar waveguide transmission line (CPW) in shunt mode, on a flexible paper substrate. The switch is based on a metal–insulator–metal structure formed respectively using Silver–Nafion–aluminum switching layers. The presented device is fully passive and shows good performance till 3 GHz, with an insertion loss less than 3 dB in the RF-on state and isolation greater than 15 dB in the RF-off state. Low-power direct current pulses in the range 10 V/0.5 mA and −20 V/0.15 A are used to operate the switch. The device was fabricated in an ambient laboratory condition, without the use of any clean room facilities. A brief discussion of the results and potential application of this concept in a re-configurable chipless RFID tag is also given in this article. This study is a proof of concept of fabrication of electronically re-configurable and disposable RF-electronic switches on low cost and flexible substrates, using a process feasible for mass production. Keywords: CBRAM; MIM switch; chipless RFID; RF-switch; electronically reconfigurable switch
1. Introduction Low-power, passive, and non-volatile RF-switches are an area of keen interest among scientists and industry in the current decade. Non-volatile switches would benefit every field of RF-engineering by drastically cutting down the power budget. With the current threshold of development in disposable printed RF electronics, the requirement for passive and low-power switches has intensified. One of the available solutions for passive, non-volatile switches are Memristive devices such as the conductive bridging random access memory (CBRAM) switches [1], phase change memory (PCM) switches [2,3], etc. These techniques utilize electrochemical properties and molecular arrangement properties of materials, respectively, to achieve the switching action. The CBRAM switch is also referred to as a metal–insulator–metal (MIM) switch owing to its switching layers construction. Working principles and details of this technology are explained in this article. In the case of PCM switches, the change from an amorphous to crystalline state and back of certain materials like germanium telluride upon application of controlled heating pulses are utilized for switching. A handful of articles have reported fine, non-volatile switches based on the above mentioned principles [1,2,4–6]. However, in the majority of cases, the fabrication technique is very much complicated and often requires a “clean room” facility. Additionally, in most cases the devices are fragile in nature and require
Technologies 2018, 6, 58; doi:10.3390/technologies6030058
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are fragileconformal in nature protection and require dedicated conformal schemes to protect it from dedicated schemes to protect it fromprotection the ambient atmosphere, and thus addsthe to ambient the total atmosphere, cost budget. and thus adds to the total cost budget. In design, development, development, and In this this article article for for the the first first time time we we present present the the design, and application application of of aa simple simple and robust CBRAM CBRAMbased basedMIM MIM RF-switch a flexible paper substrate. Inexperiment, this experiment, the and robust RF-switch on on a flexible paper substrate. In this the entire entire fabrication was out carried out in laboratory ambient laboratory conditions, without the clean use ofroom any device device fabrication was carried in ambient conditions, without the use of any clean room Inwe this study, we aim to prove the feasibility ofa MIM integrating MIM switch in facilities. In facilities. this study, aim to prove the feasibility of integrating switchain electronically electronically RF devices on flexible and low-cost substrates likeseen paper, which are reconfigurablereconfigurable RF devices on flexible and low-cost substrates like paper, which are around in our seen around in our daily life as packaging materials for goods, transport tickets, and visiting cards. daily life as packaging materials for goods, transport tickets, and visiting cards. An An RF-identification RF-identification tag tag using using the the RF-encoding RF-encoding particle particle proposed proposed in in this this paper paper could could be be easily easily fabricated on aa paper paper substrate substrate with with an an adhesive adhesive background, background, and fabricated as as aa sticker, sticker, on and could could be be attached attached to to an object, like a barcode sticker, with far more advanced functionalities in comparison to the optical an object, like a barcode sticker, with far more advanced functionalities in comparison to the optical barcodes, like identification identification out out of of the the optical-line-of-sight, optical-line-of-sight, electronic electronic reconfigurability, reconfigurability,etc. etc. barcodes, like 2. Motivation and Background The basic building block block of of the the presented presentedRF-switch RF-switchisisaanano-ionic nano-ionicMIM MIMswitching switchingcell. cell.Figure Figure1 1shows shows basic layer structure working principle of proposed the proposed switching technique. The thethe basic layer structure andand working principle of the switching technique. The MIM MIM is comparable to a plate parallel plate in capacitor in electrolyte which theiselectrolyte by an cell is cell comparable to a parallel capacitor which the replaced byisanreplaced ion-conductor, ion-conductor, which is an electrically insulating material, such as ‘Poly(methyl methacrylate)’ which is an electrically insulating material, such as ‘Poly(methyl methacrylate)’ (PMMA) [7], doped (PMMA) [7], doped [4], Nafion [8],of etc. of the cell is an ion-donor Chalcogenide glass Chalcogenide [4], Nafion [8],glass etc. One electrode theOne cellelectrode is an ion-donor metal-like silver or metal-like silver or copper, generally calledand the the active electrode, and the other is like a relatively inert copper, generally called the active electrode, other is a relatively inert metal aluminum or metal likethe aluminum or gold. On the field application of antoelectric field from active inert electrodes electrode, gold. On application of an electric from active inert electrode, ions fromtoactive ions active electrodes under thea filament influencetoofinert thiselectrode field grow a filament to inert electrode underfrom the influence of this field grow through the ion-conductor layer. through thethe ion-conductor layer. closeswith the switch, to form the Set state, with a low resistance This closes switch, to form theThis Set state, a low resistance across the cell. Similarly, a field of across thedirection cell. Similarly, field of opposite direction usedthe to dissolve filament andstate, openwith the opposite is usedato dissolve the filament andisopen switch tothe form the reset switch form theacross reset state, with a high resistance across thetocell. The switch once not commuted a a high to resistance the cell. The switch once commuted a stable state does require to any stable state power does not require anyitsmaintaining supply topassive retain device. its state, making it a maintaining supply to retain state, makingpower it a non-volatile Power is applied non-volatile is applied to theequivalent switch only to change state. An electrical to the switchpassive only todevice. changePower its state. An electrical model of the its MIM switch could be equivalent model the MIM switch couldinbe approximated to a parallel plateas capacitor inFigure parallel approximated to aof parallel plate capacitor parallel to the filament resistance, shown in 1, to the Cfilament resistance, as shown in Figure 1, where C MIM is equivalent capacitance due to where is equivalent capacitance due to geometry of electrodes and R is equivalent filament MIM MIM geometry electrodes and RMIM is equivalent filament resistance across the cell. resistance of across the cell.
Figure Figure 1. 1. Layer Layer architecture architecture of of metal–insulator–metal metal–insulator–metal (MIM) (MIM) cell cell showing showing the the filament filament formation formation and and dissolution, along with the electrical equivalent circuit. dissolution, along with the electrical equivalent circuit.
Figure 2 shows 100 switching cycles for a typical MIM cell with Nafion as an ion-conductor v/s Figure 2 shows 100 switching cycles for a typical MIM cell with Nafion as an ion-conductor v/s filament resistance. We have not yet done a full-fledged study to find out the maximum number of filament resistance. We have not yet done a full-fledged study to find out the maximum number functional cycles or the switching time of the MIM cell, to preserve the devices for detailed of functional cycles or the switching time of the MIM cell, to preserve the devices for detailed RF-characteristics analysis. This will be carried out in near future. RF-characteristics analysis. This will be carried out in near future.
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Figure 2. One-hundred switching cycles of a typical MIM cell with Nafion as the ion-conductor. Figure 2. 2. One-hundred switching cycles cycles of of aa typical typical MIM MIM cell cell with with Nafion Nafion as as the the ion-conductor. ion-conductor. Figure One-hundred switching
3. Design and Construction 3. Design Design and and Construction Construction 3. The presented design is a modified version of the predecessor reported in reference [8]. The The presented presented design a [8] modified version the predecessor reported in reference [8]. The The design is aismodified of theofpredecessor reported intransmission reference [8]. line The switch reported reported version in this article is a version 50 Ω co-planar waveguide (CPW) in reported version in this article [8] is a 50 Ω co-planar waveguide (CPW) transmission line switch in version in this article [8] is a 50 Ω co-planar waveguide (CPW) transmission line switch in shunt mode shunt mode on FR-4 substrate, similar to the one shown in Figure 3. This device is fully fabricated in shunt mode on FR-4 substrate, touse theinone shown in Figure 3. is This device fullyinfabricated in on substrate, similar towithout thesimilar one the shown 3. This device fully fabricated an ambient anFR-4 ambient environment ofFigure any clean room facilities. The is device shows good an ambient environment without the use of any clean room facilities. The device shows good environment of any The device good performance features performancewithout featurestheatuse least up clean to 3 room GHz facilities. in comparison withshows existing switching technologies performance features at least up to 3 GHz in comparison with existing switching technologies at least up The to 3 GHz comparison with existing switching technologies available. The CPW shunt available. CPW in shunt mode design was chosen over the simple microstrip design to avoid the available. The CPW shunt mode design was chosen over the to simple microstrip designdifficulties to avoid the mode design was chosen over the simple microstrip design avoid the fabrication in fabrication difficulties in ambient laboratory conditions. With the microstrip design, there are size fabrication difficulties in ambient laboratory conditions. With the microstrip there size ambient laboratory conditions. With the microstrip design, there size limitations on the dimensions limitations on the dimensions of the switching area in order toare limit very highdesign, capacitance atare higher limitations onThis the dimensions the very switching area in order to limit veryishigh capacitance at having higher of the switching area in orderhaving toof limit high at higher frequencies. This requires frequencies. requires smallcapacitance dimensions than what used in this study. The frequencies. This requires having very small dimensions than what is used in this study. The very small dimensions than what isisused in this study. The photograph this realization is depicted photograph of this realization depicted in Figure 4a and theof inset shows the close-up photograph of the this realization is close-up depicted in Figure 4a and inset shows in Figure 4a and shows the of thethe MIM switch area. the close-up microphotograph ofinset the MIM switch area. microphotograph microphotograph of the MIM switch area.
Figure3.3.Geometry Geometry (a) layer and layer architecture used in thewaveguide co-planar (CPW) waveguide (CPW) Figure (a) and architecture (b) used(b) in the co-planar transmission Figure 3. Geometry (a)mode andRF-Switch. layer architecture (b) used in the co-planar waveguide (CPW) transmission line shunt line shunt mode RF-Switch. transmission line shunt mode RF-Switch.
In this article we try the same technology on a flexible paper substrate. The topology and In we the same on aaflexible paper substrate. The topology In this this article article we try tryare thegiven sameintechnology technology onprocesses flexibleused paper topologyinand and dimensions of the switch Figure 3. The for substrate. fabricationThe are detailed the dimensions of the switch are given in Figure 3. The processes used for fabrication are detailed in the dimensions of the switch are given in Figure 3. The processes used for fabrication are detailed in the following paragraphs. following paragraphs. following paragraphs. The substrate used for the fabrication of the device was 80 g per sq. meter (GSM) special quality The substrate used for fabrication of device was 80 gg per meter special quality The substrate used for the the of the the per sq. sq.treated meter (GSM) (GSM) special quality RF-paper developed at the IES fabrication lab. This paper is device flexiblewas and80specially to reduce the losses at RF-paper developed at the IES lab. This paper is flexible and specially treated to reduce the losses RF-paper developed at the IES lab. This paper is flexible and specially treated to reduce the losses at radiofrequencies, and also has an improved surface for better adhesion of metal layers. Metal layers at radiofrequencies, and an improved surface for better adhesion of metal layers. Metal radiofrequencies, and alsoalso hashas anthermal improved surface for better adhesion of metal layers. Metal layers were formed on the substrate by vapor deposition of silver (active electrode) and aluminum layers were formed on the substrate by vapor thermal vapor deposition of silver (active electrode) and were formed on the substrate by thermal deposition of silver (active electrode) and aluminum (inert electrode). Thermal vapor deposition was done with the help of dedicated nickel masks which aluminum (inert electrode). Thermal vapor deposition was done with the help of dedicated nickel (inert Thermal vapor wastopology done withinthe help of nickel masks carry electrode). an engraved aperture of deposition the presented Figure 3. dedicated After formation of the which active masks which carry an engraved aperture of thetopology presented topology inAfter Figure 3. After formation of carry an engraved aperture of the presented in Figure 3. formation of electrode, the electrolyte layer was formed by spin coating the Nafion solution (suppliedthe by active Sigma the active electrode, the electrolyte layer was formed by spin coating the Nafion solution (supplied by electrode, the electrolyte layeratwas formed spinfor coating the formed Nafion solution by Sigma Aldrich, St. Louis, MO, USA) a rate of 500byRPM 30 s. The layer was(supplied then air dried on a Sigma Aldrich, St. Louis, MO, USA) at a rate of 500 RPM for 30 s. The formed layer was then air dried Aldrich, a rate 500 RPM for 30was s. The formed layer was then airdeposition. dried on a hot plateSt. atLouis, 100 °CMO, 2USA) min. at Then theofinert electrode formed using thermal vapor ◦for on a plate hot plate at 100 C for 2 min. Then the inert electrode wasformed formedusing usingthermal thermalvapor vapor deposition. deposition. hot at 100 °C for 2 min. Then the inert electrode was Detachable SMA connectors are then attached to the device to feed RF power. Detachable SMA connectors are then attached to device to feed Detachable SMA connectors attached to the the device feedRF RFpower. power. It is now apparent that are thethen proposed switch could be to integrated into most RF-designs using a It is now apparent that the proposed switch could be integrated most RF-designs using a three-step process: (1). Deposition of active electrode. (2). Depositioninto of electrolyte/ion-conductor. three-step process: (1). Deposition of active electrode. (2). Deposition of electrolyte/ion-conductor.
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It is now apparent that the proposed switch could be integrated into most RF-designs using a Technologies 2018, 6, x FOR PEER REVIEW 4 of 10 three-step process: (1) Deposition of active electrode; (2) Deposition of electrolyte/ion-conductor; (3) bebe easily carried outout in in an an industrial environment by (3).Inert Inertelectrode electrodedeposition. deposition.These Thesesteps stepscould could easily carried industrial environment techniques like flexography [9]. The use of silver metal in the tags could be limited to the switch area by techniques like flexography [9]. The use of silver metal in the tags could be limited to the switch only, by adjusting the nickel maskmask design, so as so to reduce further the cost realization. area only, by adjusting the nickel design, as to reduce further theofcost of realization. A photograph of the fabricated CPW shunt mode switch on paper substrate is shown in Figure 4b A photograph of the fabricated CPW shunt mode switch on paper substrate is shown in Figure and the inset shows the microphotograph of MIM switch area revealing the sandwich structure. 4b and the inset shows the microphotograph of MIM switch area revealing the sandwich structure. The was measured to to be be 1.3 1.3 µmµm andand 1 µm, respectively, and The thickness thicknessof ofsilver silverand andaluminum aluminumdeposit deposit was measured 1 µm, respectively, that of the Nafion deposit is 600 nm. The measurement was carried out with the help of a Dektak-150 and that of the Nafion deposit is 600 nm. The measurement was carried out with the help of a mechanical Dektak-150 Profilometer. mechanical Profilometer. Nafion Nafion [8] [8] was was chosen chosen as as the the ion-conductor ion-conductor in in this this realization realization due due to to some some specific specific advantages advantages inherent to this polymer in contemplation to materials used classically [4]. Nafion inherent to this polymer in contemplation to materials used classically [4]. Nafion is is aa sulfonated sulfonated tetrafluoroethylene well well known for its fast properties tetrafluoroethylenebased basedfluoropolymer-copolymer, fluoropolymer-copolymer, known for ion its conducting fast ion conducting ◦ and use in proton-exchange-membrane fuel cells, and stableand up is tostable 190 Cup [10]. Nafion layerNafion could properties and use in proton-exchange-membrane fueliscells, to 190 °C [10]. ◦ C. From our be easily formed by spin coating and could be air dried at temperatures around 100 layer could be easily formed by spin coating and could be air dried at temperatures around 100 °C. experience in realization, this material stable inisambient and does an additional From our experience in realization, thisismaterial stable inairambient airnot andrequire does not require an conformal coating for protection. The maximum temperature observed on the sample during the additional conformal coating for protection. The maximum temperature observed on the sample ◦ C. thermal vapor deposition was around 120 during the thermal vapor deposition was around 120 °C. The The working working of of the the presented presented CPW CPW shunt shunt mode mode switch switch could could be be explained explained with with reference reference to to Figure 3. The MIM switch structure is formed in this device between the 100 µm wide shunt Figure 3. The MIM switch structure is formed in this device between the 100 µm wide shunt line line and and 300 300 µm µm wide wide transmission transmission line, line, sandwiching sandwiching the the 600 600 nm nm layer layer of of Nafion. Nafion. The The shunt shunt line line connectes connectes the two ground planes on the either side of the CPW line. When the MIM switch is set as the two ground planes on the either side of the CPW line. When the MIM switch is set as shown shown in in Figure 1, at the switch area labeled in Figure 3b, RF power from port 1 is short circuited to Figure 1, at the switch area labeled in Figure 3b, RF power from port 1 is short circuited to ground, ground, thus it from from port port 2. 2. This This is is the the RF-off RF-off state state of of the the switch. switch. When When the the MIM MIM switch switch is thus disconnecting disconnecting it is reset reset as shown in Figure 1, the short is removed and port 1 is connected to port 2, forming the RF-on state. as shown in Figure 1, the short is removed and port 1 is connected to port 2, forming the RF-on state.
(a)
(b)
Figure 4.4.Photographs Photographs of the fabricated RF-switch on FR-4 classic FR-4 substrate and on paper Figure of the fabricated RF-switch on classic substrate (a), and on(a), paper substrate (b). substrate (b). Inset of both photographs shows the microphotograph of the MIM switch area. Inset of both photographs shows the microphotograph of the MIM switch area.
Direct current pulses used for operating the switch are given in Figure 5. In order to ensure Direct current pulses used for operating the switch are given in Figure 5. In order to ensure smooth and stable operation of the switch, a positive growing current limited triangular wave form smooth and stable operation of the switch, a positive growing current limited triangular wave form of peak voltage 10 V/0.5 mA is used for the set and a flat −20 V/0.15 A square wave is used for the of peak voltage 10 V/0.5 mA is used for the set and a flat −20 V/0.15 A square wave is used for the reset, as shown in the plot. These wave forms were optimized by various trial and error experiments. reset, as shown in the plot. These wave forms were optimized by various trial and error experiments. In the case given in Figure 5, the switch is set at 7.5 V and reset at −20 V, power consumed for the set In the case given in Figure 5, the switch is set at 7.5 V and reset at −20 V, power consumed for the set and reset are calculated as 0.76 mW and 9.6 mW, respectively. These power values were calculated and reset are calculated as 0.76 mW and 9.6 mW, respectively. These power values were calculated from the instantaneous value of set/reset voltage and current pulses. An abrupt fall in the measured voltage across the switch and rise in current during the set pulse indicates a set state by the formation of a low resistance filament from active to inert electrode in the MIM Cell (see Figure 5). Similarly, an abrupt rise in voltage and fall in current during the reset pulse indicates dissolution of filament and establishment of a high-resistance reset state across the MIM cell. The set/reset pulses
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from the instantaneous value of set/reset voltage and current pulses. An abrupt fall in the measured voltage across the switch and rise in current during the set pulse indicates a set state by the formation of a low resistance filament from active to inert electrode in the MIM Cell (see Figure 5). Similarly, Technologies 2018, 6, x FOR PEER REVIEW 5 of 10 an abrupt rise in voltage and fall in current during the reset pulse indicates dissolution of filament and establishment of the a high-resistance reset state MIMmetallic cell. The set/reset pulsestowere applied to were applied to switch with the help of across customthe made probes attached metallic parts thethe switch with the help of custom made metallic probes attached to metallic parts of the switch. of switch.
Figure 5. Direct current (DC) pulses used to operate the switch.
4. Results RF response of the switch is given in Figure 6. Measurements of the device were done using Agilent ENA E5061B (3 GHz) Network Analyzer, using the Short-Open-Load-Thru calibration scheme. The power level used for the test was −15 dBm. The RF-switch shows acceptable performance up to 3Figure GHz with an current insertion loss less used than 3 dB in the 5. pulses operate the switch. Figure 5. Direct Direct current (DC) (DC) pulses used to to operate theRF-on switch.condition and isolation greater than 15 dB in the entire band in the RF-off condition. Filament resistance values for the 4.respective Results 4. Results Set and reset are given in brackets of the respective legends for each cycle of operation. We RF were able to of achieve filament resistance values of 4 Ω and 60 kΩ, respectively, fordone the set and response the switch is given in Figure 6. Measurements of the device were using RF response of the switch is given in Figure 6. Measurements of the device were done using reset states. Agilent ENA E5061B (3 GHz) Network Analyzer, using the Short-Open-Load-Thru calibration Agilent E5061B (3 GHz) Network Analyzer, using the Short-Open-Load-Thru calibration scheme. InENA this maximum Ω and the minimum reset scheme. The experiment, power level the used for the set testresistance was −15 value dBm. was The 10 RF-switch shows acceptable The power level used for the test was − 15 dBm. The RF-switch shows acceptable performance up to resistance value 40 kΩ. is a goodloss RReset /RSetthan value. realization of isolation the CPW performance up towas 3 GHz withThis an insertion less 3 dBRFinresponse the RF-onofcondition and 3shunt GHz with an insertion loss less than 3 dB in the RF-on condition and isolation greater than 15 dB switch classical [8] is condition. given in Figure 7 forresistance comparison. Thisfor device greater mode than 15 dB inonthe entire FR-4 bandsubstrate in the RF-off Filament values the inshows the entire band inloss the RF-off condition. Filament resistance values for the respective Setstate. and reset an insertion less than 1 dB in RF-on state and greater than 16 dB in the RF-off From respective Set and reset are given in brackets of the respective legends for each cycle of operation. are in brackets of the respective legends eachsubstrate cycle of operation. We were able to achieve thisgiven response it achieve is clear that the realization onfor paper has acceptable performance. We were able to filament resistance values of 4 Ω and 60 kΩ, respectively, for the setMinor and filament resistance values of 4 Ω and 60 kΩ, respectively, for the set and reset states. degradation reset states. in the on-state insertion loss could be justified by the losses inherent to paper substrate. In this experiment, the maximum set resistance value was 10 Ω and the minimum reset resistance value was 40 kΩ. This is a good RReset/RSet value. RF response of realization of the CPW shunt mode switch on classical FR-4 substrate [8] is given in Figure 7 for comparison. This device shows an insertion loss less than 1 dB in RF-on state and greater than 16 dB in the RF-off state. From this response it is clear that the realization on paper substrate has acceptable performance. Minor degradation in the on-state insertion loss could be justified by the losses inherent to paper substrate.
(a)
(b)
Figure 6. RF-response of the Co-Planar Waveguide (CPW) shunt mode switch on paper substrate. (a) Figure 6. RF-response of the Co-Planar Waveguide (CPW) shunt mode switch on paper substrate. S21; (b) S11. (a) S21; (b) S11.
In this experiment, the maximum set resistance value was 10 Ω and the minimum reset resistance value was 40 kΩ. This is a good RReset /RSet value. RF response of realization of the CPW shunt (a) (b) mode switch on classical FR-4 substrate [8] is given in Figure 7 for comparison. This device shows an Figure 6. RF-response of the Co-Planar (CPW) paper substrate. (a) insertion loss less than 1 dB in RF-on stateWaveguide and greater than shunt 16 dBmode in theswitch RF-offon state. From this response S21; (b) S11.
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it is clear that the realization on paper substrate has acceptable performance. Minor degradation in the on-state insertion lossPEER could be justified by the losses inherent to paper substrate. Technologies 2018, 6, x FOR REVIEW 6 of 10
(a)
(b)
Figure 7. RF-response of the Co-Planar Waveguide (CPW) shunt mode switch on FR-4 substrate. (a) Figure 7. RF-response of the Co-Planar Waveguide (CPW) shunt mode switch on FR-4 substrate. S21; (b) S11. (a) S21; (b) S11.
Table 1 is a comparison of the features of the proposed RF-switch on paper substrate with the Table 1 is adesign comparison of theonfeatures of thesubstrate. proposed RF-switch on paper substrate with the state-of-the-art and design classic FR-4 state-of-the-art design and design on classic FR-4 substrate. Table 1. Comparison of proposed device to the state-of-the-art. Table 1. Comparison of proposed device to the state-of-the-art. Proposed Design Design on FR4 State of the Art Features on Proposed Paper Substrate [8] (Nano-Ionic Design on State ofSwitch) the Art [4] Features Design on FR4 [8] Paper Substrate (Nano-Ionic Switch) [4] Min. fabrication size requirement 100 µm 100 µm 10 µm Min.Frequency fabrication size requirement 100GHz µm 100GHz µm 10 µm range DC—3 DC—3 DC—6 GHz −16 DC—3 dB to −34 Frequency range DC—3 GHz GHz DC—6 GHz Isolation (avg.) (off state) −23 dB −35 dB Isolation (avg.) (off state) −23 dB −16 dB dB to −34 dB −35 dB Insertion loss (avg.) (on state) 1.2 dB 0.5 dB 0.5 Insertion loss (avg.) (on state) 1.2 dB 0.5 dB 0.5dB dB Actuation voltage ~10 V/−20 V * ~10 V/−20 V * ~1 V Actuation voltage ~10 V/−20 V * ~10 V/−20 V * ~1 V Power consumption µW/Mw * µW/mW * µW Power consumption µW/Mw * µW/mW * µW Energy consumption to maintain 0 0 0 0 00 Energy consumption to maintain state state ‘Set’—resistance (avg.) ‘Set’—resistance (avg.) 7 Ω7 Ω 2–52–5 ΩΩ 1010ΩΩ Switching speed Switching speed Alignment accuracy required for fabrication Alignment accuracy required for
fabrication
# # Low
Low
Number of fabrication steps
Number of fabrication steps Fabrication environment
Fabrication environment Fabrication cost (laboratory perspective)
# # Low
Low
3
6
Ambient room
Ambient room
3
6
1–10µs µs 1–10 Very High
Very High
6 (Clean Room Procedures) 6 (Clean Room Procedures) Clean room Clean room High
AmbientLow room AmbientLow room Fabrication cost (laboratory Fabrication cost (industrial perspective) Low Low Moderate Low Low High perspective) * For set/reset, respectively. # At present, we do not have enough information for calculating the switching time of Fabrication cost (industrial the presented device. Low Low Moderate perspective)
* For set/reset, respectively. # At present, we do not have enough information for calculating the 5. Potential Applications switching time of the presented device.
This idea of fabrication of RF-switches is seen to be functional and feasible in several applications in the fieldApplications of disposable RF-electronics, in devices such as reconfigurable Radio Frequency 5. Potential Identification (RFID)tags [11,12], reconfigurable filters, and reconfigurable antennas. This idea of fabrication of RF-switches is seen to be functional and feasible in several applications in the field of disposable RF-electronics, in devices such as reconfigurable Radio Frequency Identification (RFID)tags [11,12], reconfigurable filters, and reconfigurable antennas. Radio frequency identification or RFID is a multi-dimensional ingenious concept that has evolved in the past couple of decades and is still advancing at a very high speed. RFID finds application in an all-round domain from identification, sensing, energy, harvesting, etc. [12–14].
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Radio frequency identification or RFID is a multi-dimensional ingenious concept that has evolved Technologies 6, x FOR PEER REVIEW 10 in the past2018, couple of decades and is still advancing at a very high speed. RFID finds application 7inofan Technologies 2018, 6, xfrom FOR PEER REVIEW 7 of 10 all-round domain identification, sensing, energy, harvesting, etc. [12–14]. Amongst this, this, the the chipless-RFID chipless-RFID technology technology is is an an innovative innovative identification identification technique technique often often Amongst referred to as the “barcode of the future” due to its various versatile functionalities like large read Amongst this, the chipless-RFID technology anvarious innovative identification technique often referred to as the “barcode of the future” due toisits versatile functionalities like large range without optical contact, sensor integration [11,14,15], etc.,etc., which cannot referred towithout as the “barcode of the future” due to its functionality various versatile functionalities likewhich large read be read range optical contact, sensor integration functionality [11,14,15], cannot range without optical contact, sensor integration functionality [11,14,15], etc., which cannot be to implemented in the current scenario, with the optical barcode technology. Still, a limiting factor be implemented in the current scenario, with the optical barcode technology. Still, a limiting factor to implemented inof thethis current scenario,iswith the optical barcode technology. Still, atolimiting factor to widespread use technology the cost per unit tag in comparison optical barcodes. widespread use of this technology is the cost per unit tag in comparison to optical barcodes. However, widespread use developments of this technology is the per unit tagprinted in comparison to optical barcodes. However, recent fieldcost ofprinted disposable RF-electronics would lift this recent developments in the field in of the disposable RF-electronics would lift this technique to However,to recent developments in the field of disposable printedtoRF-electronics wouldfor lift adding this technique the technology mainstream in near future. Thanks CBRAM switches the technology mainstream in near future. Thanks to CBRAM switches for adding revolutionary technique toreconfigurability the technology mainstream in tonear future. Thanks to CBRAM switches for adding revolutionary thetags, chipless RFID tags, which helps reconfigurability functionality tofunctionality the chipless RFID which helps in reducing cost in perreducing unit tag cost and revolutionary reconfigurability functionality to the chipless RFID tags, which helps in reducing cost per unit tag and increases the versatility of this technique. increases the versatility of this technique. perAn unitexample tag and increases the versatility of this of technique. of the potential potential advantage using the the proposed proposed switch switch technology technology could could be be AnAnexample exampleofofthe the potential advantage advantage of of using using the proposed switch technology could be explained as as follows. follows. Figure Figure 8 shows the the method of of frequency frequency shift shift coding coding of of RF-encoding RF-encoding particles particles explained explained as follows. Figure88shows shows the method method of frequency shift coding of RF-encoding particles (REP) in a chipless RFID tag [10,14]. In this example, a shorted dipole resonator is used as the REP. (REP) in in a chipless example,aashorted shorteddipole dipoleresonator resonator is used REP. (REP) a chiplessRFID RFIDtag tag[10,14]. [10,14]. In In this this example, is used as as thethe REP. Classically, this is achieved by modifying the dimensions of each REP on the tag as shown in Figure Classically, this is is achieved bybymodifying as shown shown in inFigure Figure 8. Classically, this achieved modifyingthe thedimensions dimensionsof ofeach each REP REP on on the tag as 8. For this,unique a unique geometry be designed for each REP. But instead, if we introduce the For geometry has tohas be to designed for each instead, if we introduce the proposed 8.this, For athis, a unique geometry has to be designed forREP. eachBut REP. But instead, if we introduce the proposed MIM switch technique to this REP as shown in Figure 8, the same performance could be MIM switch MIM technique totechnique this REP as in as Figure 8, the same performance could be achieved with proposed switch to shown this REP shown in Figure 8, the same performance could be with a ageneral REP dimension, byswitching electronically switching the MIM cell. achieved with general REPof offixed fixed dimension, by electronically switching MIM cell. aachieved general REP of fixed dimension, by electronically the MIM cell. the
Figure 8. Concept of application of MIM switches in RF-encoding an RF-encoding particles (REP) chipless Figure of of MIM switches in an particles (REP) for for chipless radio Figure 8.8. Concept Conceptofofapplication application MIM switches in an RF-encoding particles (REP) for chipless radio frequency identification (RFID) tag. frequency identification (RFID) tag. radio frequency identification (RFID) tag.
If we integrate such REPs depending on how much bit density is required, on a credit card size we integrate integratesuch suchREPs REPsdepending dependingononhow how much density is required, a credit If we much bitbit density is required, on aoncredit cardcard size size tag, tag, with contact pad and set/reset lines, it forms a general reconfigurable chipless RFID card. This tag, with contact padset/reset and set/reset it forms a general reconfigurable chipless RFID This card.could This with contact pad and lines,lines, it forms a general reconfigurable chipless RFID card. could be programmed by a dedicated logic device similar to a credit card reader to encode could be programmed by a be dedicated deviceto similar to amode credit card to encode be programmed by then a dedicated logic similar a credit card reader to encode information. information. And could useddevice for logic identification in wireless similar toreader a conventional information. And then could be used for identification in wireless mode similar to a conventional And then could be used for identification in wireless mode similar to a conventional chipless RFID tag. chipless RFID tag. An illustration of this idea is depicted in Figure 9. chipless RFID tag. Anidea illustration of this idea is 9. depicted in Figure 9. An illustration of this is depicted in Figure
Figure 9. Conceptual illustration of an electronically reconfigurable chipless RFID tag.
Figure 9. Conceptual illustration of an electronically reconfigurable chipless RFID tag.
Figureof 9. concept Conceptual illustration of aniselectronically RFID 10a,b tag. shows, The proof of this technique reported in reconfigurable Reference [10],chipless and Figure respectively, the photograph and response of a similar design on a flexible paper substrate. The proof of concept of this technique is reported in Reference [10], and Figure 10a,b shows, Fabrication of this tag is carried out in similar way like the RF-switch on paper substrate, by thermal respectively, the photograph and response of a similar design on a flexible paper substrate. vapor deposition of silver (active) and aluminum (inert) electrodes, and spin coating of Nafion. The
Fabrication of this tag is carried out in similar way like the RF-switch on paper substrate, by thermal vapor deposition of silver (active) and aluminum (inert) electrodes, and spin coating of Nafion. The
proposed design is inspired from the “C” resonator reported in Reference [16]. Here we use a MIM proposed design is inspired from the “C” resonator reported in Reference [16]. Here we use a MIM switch, as shown in Figure 10a with silver-Nafion-aluminum layers, to reconfigure the resonator by switch, as shown in Figure 10a with silver-Nafion-aluminum layers, to reconfigure the resonator by tuning its electrical equivalent circuit depending on the filament resistance (of the nano-ionic tuning its electrical equivalent circuit depending on the filament resistance (of the nano-ionic filament in the MIM cell). Equivalent circuit analysis and simulation studies of this concept are filament in the MIM cell). Equivalent circuit analysis and simulation studies of this concept are reported 2018, in Reference [10]. Figure 11 shows the experimental bistatic radar setup using Agilent Technologies 6, 58 8 of 10 reported in Reference [10]. Figure 11 shows the experimental bistatic radar setup using Agilent N5222A PNA and two wide-band horn antennas in co-polarization in an anechoic chamber [16]. N5222A PNA and two wide-band horn antennas in co-polarization in an anechoic chamber [16]. This setup is used to record the RCS response of the tag shown in Figure 10. It is apparent from these This The setupproof is used to recordof the RCS responseisofreported the tag shown in Figure 10. and It is apparent fromshows, these concept this technique in Reference Figure 10a,b results that weofare able to switch the tag at two different resonant [10], frequencies separated by 400 results that we able to switch the tagofat two different resonant frequencies separated by 400 respectively, the are photograph response a similar design on a flexible paper substrate. Fabrication MHz, with set/reset positionand of the MIM switch. MHz, with set/reset position of the MIM switch. of this tag is carried out in similarofway the RF-switch on paper byand thermal vapor Discussion on the application thislike concept for commercial masssubstrate, production use, and the Discussion on (active) the application of this concept for commercial mass production andThe use,proposed and the deposition of silver and aluminum (inert) electrodes, and spin coating of Nafion. expected convenience is explained in the following paragraphs. expected isthe explained in the following paragraphs. design is convenience inspired from “C” resonator reported Reference [16]. Here we use MIM switch, as Vena et al. [17] reports a 20-bit chipless RFID in tag. Let us suppose to use thisaparticular tag for Vena et al. [17] reports a 20-bit chipless RFID tag. Let us suppose to use this particular tag for shown in applications Figure 10a with silver-Nafion-aluminum layers, to reconfigure the resonator by tuning its labeling in which the tag is encoded by using two different dimensions for each labeling applications in which the tag is encoded by using(of two different dimensions for each electrical equivalent circuit depending on the filament resistance the nano-ionic filament in the MIM resonator. Thus, by using the well-known frequency shift coding technique [14], Expression (1) resonator. Thus, by using the well-known frequency of shift technique [14], Expression (1) cell). analysis and simulation thiscoding concept [10]. couldEquivalent be used tocircuit compute the possible numberstudies of combinations (referare to reported Figure 8 in forReference illustration of could be used to compute the possible number of combinations (refer to Figure 8 for illustration of Figure 11 shows the experimental bistatic radar setup using Agilent N5222A PNA and two wide-band the concept of bandwidth allocation for each resonator). the concept of bandwidth allocation foranechoic each resonator). horn antennas in co-polarization in an chamber [16]. This setup is used to record the RCS k
response of the tag shown in Figure 10. It is apparent these results that we are able to switch k Δf from (1) Nseparated =Δf by 400 MHz, with set/reset position of the the tag at two different resonant frequenciesN (1) = df MIM switch. df
(a) (a)
(b) (b)
Figure 10. Photograph (a) and measured |RCS| response (b) of of thereconfigurable reconfigurable RF-tag on paper substrate. Figure 10. Photograph measured |RCS|response response(b) (b) RF-tag on on paper substrate. Figure 10. Photograph (a) (a) andand measured |RCS| of the the reconfigurable RF-tag paper substrate.
Figure 11. Bistatic radar setup used for RCS measurements of the Tag. Figure 11. Bistatic radar setup used for RCS measurements of the Tag. Figure 11. Bistatic radar setup used for RCS measurements of the Tag.
In Expression (1), ∆f is the allocated bandwidth per resonator, df is the bandwidth of resonance In Expression (1), ∆f is the allocated bandwidth per resonator, df is the bandwidth of resonance of the resonator, kthe is the number of of this resonators on the tag, and mass N is the total number of and possible Discussion application concepton forthe commercial production and use, the of the resonator,on k is the number of resonators tag, and N is the total number of possible combinations. In this example let us say the allocated bandwidth per resonator is 200 MHz and each expected convenience is explained in the following paragraphs. combinations. In this example let us say the allocated bandwidth per resonator is 200 MHz and each resonator resonates with a bandwidth of 100 MHz. So each resonator use could be reconfigured by Vena resonates et al. [17] reports 20-bit chipless RFID tag.So Let us suppose this tag for resonator with a abandwidth of 100 MHz. each resonatortocould be particular reconfigured by labeling applications in which the tag is encoded by using two different dimensions for each resonator. Thus, by using the well-known frequency shift coding technique [14], Expression (1) could be used to compute the possible number of combinations (refer to Figure 8 for illustration of the concept of bandwidth allocation for each resonator).
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∆f N= df
k (1)
In Expression (1), ∆f is the allocated bandwidth per resonator, df is the bandwidth of resonance of the resonator, k is the number of resonators on the tag, and N is the total number of possible combinations. In this example let us say the allocated bandwidth per resonator is 200 MHz and each resonator resonates with a bandwidth of 100 MHz. So each resonator could be reconfigured by modifying physical size to operate in two different frequencies in the allocated bandwidth. Thus, using Expression (1) we could see that the total number of possible combinations is 1,048,576. Now if we try to fabricate the required combination of tags using classical techniques like screen printing or photolithography, one requires 1,048,576 numbers of masks for the realization of the entire stretch of tags. The beauty of the proposed concept could be revealed in the following sentences, taking into consideration the amount of labor and number of masks required for the fabrication. If a MIM switch is introduced to each resonator as in Reference [10] to switch resonators between two different frequencies, then it is apparent from the presented work that the switch/tag could be fabricated using just two masks and spin coating of Nafion. Similarly, for this particular RFID tag, the entire stretch of tags could be fabricated as a general tag using just two masks. Then, a dedicated electronic pulse programming circuit with an electrode array could be used to set/reset the respective switches and to encode each tag. In essence, the complexity of requirement of the 1,048,576 unique masks for fabrication is solved by just using two masks and a dedicated programmer circuit. This example clearly indicates the leverage of application of this technology in reconfigurable chipless RFID tags. 6. Conclusions In this article, we have presented the design, construction and response of CPW shunt mode switch on flexible paper substrate. The speciality of this application is the simplicity in fabrication of the device on a substrate available at a very low cost, without using any clean room facilities. The operation of the switch is tested for at least 50 cycles for several batches, and the results are repeatable and reproducible, respectively. We have also explained and proved the concept of integration of CBRAM or MIM switch technology in chipless RFID tags which are fabricated using simple steps on low-cost paper substrates. The outcomes of this experiment show a promising future for this technique. Reconfigurable chipless RFID could be the potential labels of tomorrow, backing the idea of Internet-of-Things [11,15]. This switch technique could also be applied in devices like reconfigurable filters and reconfigurable antennas in a similar way, which are in development with the authors. With these results and the imparted confidence, the authors of this article are very near to the realization of fully printed electronically reconfigurable RF-switches and chipless RFID tags on paper, using electrolyte solvents and conductive inks, using an inkjet printer. Author Contributions: Conceptualization, J.M.P., A.V. and E.P.; Methodology, J.M.P.; Software, J.M.P., A.V. and E.P.; Validation, J.M.P., A.V., B.S. and E.P.; Writing—Original Draft Preparation, J.M.P.; Writing—Review & Editing, J.M.P., A.V. and E.P.; Supervision, A.V., B.S. and E.P.; Project Administration, A.V., B.S. and E.P.; Funding Acquisition, B.S. and E.P. Funding: This research is funded and supported by the Grenoble Institute of Technology, Université Grenoble Alpes, France and Institut Universitaire de France. Acknowledgments: The authors are grateful to the Institut d’Electronique et Systèmes (IES) University of Montpellier, France, for supporting this project. Conflicts of Interest: The authors declare no conflict of interest.
References 1.
Kozicki, M.N.; West, W.C. Programmable Metallization Cell Structure and Method of Making Same. U.S. Patent 5761115A, 2 June 1998.
Technologies 2018, 6, 58
2. 3.
4. 5. 6.
7. 8. 9. 10.
11. 12.
13. 14. 15. 16. 17.
10 of 10
Wang, M.; Shim, Y.; Rais-Zadeh, M. A Low-Loss Directly Heated Two-Port RF Phase Change Switch. IEEE Electron Device Lett. 2014, 35, 491–493. [CrossRef] Mahanta, P.; Munna, M.; Coutu, R.A. Performance Comparison of Phase Change Materials and Metal-Insulator Transition Materials for Direct Current and Radio Frequency Switching Applications. Technologies 2018, 6, 48. [CrossRef] Nessel, J.; Lee, R. Chalcogenide Nanoionic-Based Radio Frequency Switch. U.S. Patent 7923715B2, 12 April 2011. Pi, S.; Ghadiri-Sadrabadi, M.; Bardin, J.C.; Xia, Q. Nanoscale memristive radiofrequency switches. Nat. Commun. 2015, 6, 7519. [CrossRef] [PubMed] El-Hinnawy, N.; Borodulin, P.; Wagner, B.P.; King, M.R.; Jones, E.B.; Howell, R.S.; Lee, M.J.; Young, R.M. Low-loss latching microwave switch using thermally pulsed non-volatile chalcogenide phase change materials. Appl. Phys. Lett. 2014, 105, 013501. [CrossRef] Perret, E.; Vidal, T.L.; Vena, A.; Gonon, P. Realization of a Conductive Bridging RF Switch Integrated onto Printed Circuit Board. Prog. Electromagn. Res. 2015, 151, 9–16. [CrossRef] Jayakrishnan, M.P.; Vena, A.; Meghit, A.; Sorli, B.; Perret, E. Nafion-Based Fully Passive Solid-State Conductive Bridging RF Switch. IEEE Microwave Wirel. Compon. Lett. 2017, 27, 1104–1106. [CrossRef] Heitner-Wirguin, C. Recent advances in perfluorinated ionomer membranes: Structure, properties and applications. J. Membr. Sci. 1996, 120, 1–33. [CrossRef] Jayakrishnan, M.P.; Vena, A.; Sorli, B.; Perret, E. Solid-State Conductive-Bridging Reconfigurable RF-Encoding Particle for Chipless RFID Applications. IEEE Microw. Wirel. Compon. Lett. 2018, 28, 506–508. [CrossRef] Perret, E. Radio Frequency Identification and Sensors: From RFID to Chipless RFID; Wiley: Hoboken, NJ, USA, 2014; ISBN 978-1-84821-766-9. Lemey, S.; Agneessens, S.; Van Torre, P.; Baes, K.; Vanfleteren, J.; Rogier, H. Wearable Flexible Lightweight Modular RFID Tag With Integrated Energy Harvester. IEEE Trans. Microw. Theory Tech. 2016, 64, 2304–2314. [CrossRef] Goncalves, R.; Rima, S.; Magueta, R.; Pinho, P.; Collado, A.; Georgiadis, A.; Hester, J.; Carvalho, N.B. RFID-Based Wireless Passive Sensors Utilizing Cork Materials. IEEE Sens. J. 2015, 15, 7242–7251. [CrossRef] Vena, A.; Perret, E.; Tedjini, S. Chipless RFID Based on RF Encoding Particle: Realization, Coding and Reading System; ISTE-Elsevier: New York, NY, USA, 2016; ISBN 978-1-78548-107-9. Tedjini, S.; Karmakar, N.; Perret, E.; Vena, A.; Koswatta, R.; E-Azim, R. Hold the Chips: Chipless Technology, an Alternative Technique for RFID. IEEE Microw. Mag. 2013, 14, 56–65. [CrossRef] Vena, A.; Perret, E.; Tedjini, S. Chipless RFID Tag Using Hybrid Coding Technique. IEEE Trans. Microw. Theory Tech. 2011, 59, 3356–3364. [CrossRef] Vena, A.; Perret, E.; Tedjini, S. A Fully Printable Chipless RFID Tag with Detuning Correction Technique. IEEE Microw. Wirel. Compon. Lett. 2012, 22, 209–211. [CrossRef] © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
