Protein Adsorption Modes Determine Reversible Cell Attachment on Poly(N‐isopropyl acrylamide) Brushes

Protein adsorption and reversible cell attachment are investigated as a function of the grafting density of poly(N‐isopropyl acrylamide) (PNIPAM) brushes. Prior studies demonstrated that the thermally driven collapse of grafted PNIPAM above the lower critical solution temperature of 32 °C is not required for protein adsorption. Here, the dependence of reversible, protein‐mediated cell adhesion on the polymer chain density, above and below the lower critical solution temperature, is reported. Above 32 °C, protein adsorption on PNIPAM brushes grafted from a non‐adsorbing, oligo(ethylene oxide)‐coated surface exhibits a maximum with respect to the grafting density. Few cells attach to either dilute or densely grafted PNIPAM chains, independent of whether the polymer brush collapses above 32 °C. However, both cells and proteins adsorb reversibly at intermediate chain densities. This supports a model in which the proteins, which support reversible cell attachment, adsorb by penetrating the brushes at intermediate grafting densities, under poor solvent conditions. In this scenario, reversible protein adsorption to PNIPAM brushes is determined by the thermal modulation of relative protein‐segment attraction and osmotic repulsion.     

Color Tunable Poly (N‐Isopropylacrylamide)‐co‐Acrylic Acid Microgel–Au Hybrid Assemblies

A new class of materials that are capable of color tunability over 300 nm with a 15 °C temperature change is introduced. The materials are assembled from thermoresponsive poly (N‐isopropylacrylamide)‐co‐acrylic acid (pNIPAm‐co‐AAc) microgels, which are deposited on Au coated glass substrates. The films are also pH responsive; the temperature‐induced color change was suppressed at high pH and is consistent with the behavior of a solution of suspended microgels. The mechanism proposed to account for the observed optical properties suggests that they result from the two Au layers being separated from each other by the “monolithic” microgel film, much like a Fabry‐Pérot etalon or interferometer. It is the modulation of the distance between these two layers, facilitated by the microgel collapse transition at high temperature, that allows the color to be tuned. The sensitivity of the system presented here will be used for future sensing and biosensing applications, as well as for light filtering applications.     

In Situ Studies of Surface‐Plasmon‐Resonance‐Coupling Sensor Mediated by Stimuli‐Sensitive Polymer Linker

Hybrid plasmonic nanostructures comprising gold nanoparticle (AuNP) arrays separated from Au substrate through a temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) linker layer are constructed, and unique plasmonic‐coupling‐based surface plasmon resonance (SPR) sensing properties are investigated. The optical properties of the model system are investigated by in situ and scan‐mode SPR analysis. The swelling‐shrinking transitions in the polymer linker brush are studied by in situ contact‐mode atomic force microscopy at two different temperatures in water. It is revealed that the thickness of the PNIPAM layer is decreased from 30 to 14 nm by increasing the temperature from 20 to 32 °C. For the first time the dependence of the coupling behavior in AuNPs is investigated with controlled density on the temperature in a quantitative manner in terms of the change in SPR signals. The device containing AuNPs with optimized AuNP density shows 3.2‐times enhanced sensitivity compared with the control Au film‐PNIPAM sample. The refractive index sensing performance of the Au film‐PNIPAM‐AuNPs is greater than that of Au film‐PNIPAM by 19% when the PNIPAM chains have a collapsed conformation above lower critical solution temperature.     

Water‐Soluble Poly(N‐isopropylacrylamide)–Graphene Sheets Synthesized via Click Chemistry for Drug Delivery

Covalently functionalized graphene sheets are prepared by grafting a well‐defined thermo‐responsive poly(N‐isopropylacrylamide) (PNIPAM) via click chemistry. The PNIPAM‐grafted graphene sheets (PNIPAM‐GS) consist of about 50% polymer, which endows the sheets with a good solubility and stability in physiological solutions. The PNIPAM‐GS exhibits a hydrophilic to hydrophobic phase transition at 33 °C, which is relatively lower than that of a PNIPAM homopolymer because of the interaction between graphene sheets and grafted PNIPAM. Moreover, through π–π stacking and hydrophobic interaction between PNIPAM‐GS and an aromatic drug, the PNIPAM‐GS is able to load a water‐insoluble anticancer drug, camptothecin (CPT), with a superior loading capacity of 15.6 wt‐% (0.185 g CPT per g PNIPAM‐GS). The in vitro drug release behavior of the PNIPAM‐GS‐CPT complex is examined both in water and PBS at 37 °C. More importantly, the PNIPAM‐GS does not exhibit a practical toxicity and the PNIPAM‐GS‐CPT complex shows a high potency of killing cancer cells in vitro. The PNIPAM‐GS is demonstrated to be an effective vehicle for anticancer drug delivery.     

Microporous Polypyrrole‐Coated Graphene Foam for High‐Performance Multifunctional Sensors and Flexible Supercapacitors

This study reports on the fabrication of pressure/temperature/strain sensors and all‐solid‐state flexible supercapacitors using only polydimethylsiloxane coated microporous polypyrrole/graphene foam composite (PDMS/PPy/GF) as a common material. A dual‐mode sensor is designed with PDMS/PPy/GF, which measures pressure and temperature with the changes of current and voltage, respectively, without interference to each other. The fabricated dual‐mode sensor shows high sensitivity, fast response/recovery, and high durability during 10 000 cycles of pressure loading. The pressure is estimated using the thermoelectric voltage induced by simultaneous increase in temperature caused by a finger touch on the sensor. Additionally, a resistor‐type strain sensor fabricated using the same PDMS/PPy/GF could detect the strain up to 50%. Flexible, high performance supercapacitor used as a power supply is fabricated with electrodes of PPy/GF for its high surface area and pseudocapacitance. Furthermore, an integrated system of such fabricated multifunctional sensors and a supercapacitor on a skin‐attachable flexible substrate using liquid–metal interconnections operates well, whereas sensors are driven by the power of the supercapacitor. This study clearly demonstrates that the appropriate choice of a single functional material enables fabrication of active multifunctional sensors for pressure, temperature, and strain, as well as the supercapacitor, that could be used in wirelessly powered wearable devices.     

Perfectly Aligned,Air‐Suspended Nanowire Array Heater and Its Application in an Always‐On Gas Sensor

In spite of the excellent thermal properties of nanowires, the typical form factor of unrefined nanowires has restricted their potential use in developing ultralow power electrothermal heater and application device. In this paper, a nanowire array with a perfectly aligned geometric structure on an air‐suspended beam is proposed as a novel heating element. By locally confining the generated heat and suppressing beam conduction loss to the substrate, the proposed nanowire array heater overcomes the fundamental power consumption limits of conventional film‐type microheaters. As a result, only 2.51 mW of power is required to reach an average temperature of 300 °C, surpassing the performance of state‐of‐the‐art microheaters. The developed nanowire array heater is monolithically integrated with gas sensing nanowires to demonstrate its full capability as an ultralow power gas sensor. The fabricated device successfully detects low concentration carbon monoxide gas of 1 ppm, using less than 5 mW of power. The presented technique offers a promising pathway toward realizing always‐on gas sensors driven by battery‐powered mobile devices, which will ensure a hazardous gas‐free safe environment. In addition, the proposed strategy of employing geometrically structured nanomaterials in the electrothermal heater design enables to lead out their potential thermal capability in many other applications.     

Self‐Adhesive and Ultra‐Conformable,Sub‐300 nm Dry Thin‐Film Electrodes for Surface Monitoring of Biopotentials

Accurate and unobtrusive monitoring of surface biopotentials is of paramount importance for physiological studies and wearable healthcare applications. Thin, light‐weight, and conformal bioelectrodes are highly desirable for biopotential monitoring. This report demonstrates the fabrication of sub‐300 nm thin, dry electrodes that are self‐adhesive and conformable to complex 3D biological surfaces and thus capable of excellent quality of biopotential (surface electromyogram and surface electrocardiogram) recordings. Measurements reveal single‐day stability of up to 10 h. In addition, the bending stiffness of the sensor is calculated to be ≈0.33 pN m², which is comparable to stratum corneum, the uppermost layer of human skin, and this stiffness is over two orders of magnitude lower than the bending stiffness of a 3.0 µm thin sensor. Laminated on a prestretched elastomer, when relaxed, the sensor forms wrinkles with a period and amplitude equal to 17 and 4 µm, respectively, which these values agree with theoretical calculations. Finally, with skin vibrations of up to ≈15 µm, the sensor exhibits motion artifact‐less monitoring of surface biopotentials, in contrast to a wet adhesive electrode that shows much greater influence.     

Colorimetric Logic Gates Based on Poly(2‐alkyl‐2‐oxazoline)‐Coated Gold Nanoparticles

A straightforward end‐capping strategy is applied to synthesize xanthate‐functional poly(2‐alkyl‐2‐oxazoline)s (PAOx) that enable gold nanoparticle functionalization by a direct “grafting to” approach with citrate‐stabilized gold nanoparticles (AuNPs). Owing to the presence of remaining citrate groups, the obtained PAOx@AuNPs exhibit dual stabilization by repulsive electrostatic and steric interactions giving access to water soluble molecular AND logic gates, wherein environmental temperature and ionic strength constitute the input signals, and the solution color the output signal. The temperature input value could be tuned by variation of the PAOx polymer composition, from 22 °C for poly(2‐ⁿpropyl‐2‐oxazoline)@AuNPs to 85 °C for poly(2‐ethyl‐2‐oxazoline)@AuNPs. Besides, advancing the fascinating field of molecular logic gates, the present research offers a facile strategy for the synthesis of PAOx@AuNPs of interest in fields spanning nanotechnology and biomedical sciences. In addition, the functionalization of PAOx with xanthate offers straightforward access to thiol‐functional PAOx of high interest in polymer science.     

Stretchable and Heat‐Resistant Protein‐Based Electronic Skin for Human Thermoregulation

Silk protein is one of the a promising materials for on‐skin and implantable electronic devices due to its biodegradability and biocompatibility. However, its intrinsic brittleness as well as poor thermal stability limits its applications. In this work, robust and heat‐resistant silk fibroin composite membranes (SFCMs) are synthesized by mesoscopic doping of regenerated silk fibroin (SF) via the strong interactions between SF and polyurethane. Surprisingly, the obtained SFCMs can endure the tensile test (>200%) and thermal treatment (up to 160 °C). Attributed to these advantages, traditional micromachining techniques, such as inkjet printing, can be carried out to print flexible circuits on such protein substrate. Based on this, Ag nanofibers (NFs) and Pt NFs networks are successfully constructed on both sides of the SFCMs to function as heaters and temperature sensors, respectively. Furthermore, the integrated protein‐based electronic skin (PBES) exhibits high thermal stability and temperature sensitivity (0.205% °C^?1). Heating and temperature distribution detection are realized by array‐type PBES, contributing to potential applications in dredging of the blood vessel for alleviating arthritis. This PBES is also inflammation‐free and air‐permeable so that it can directly be laminated onto human skin for long‐term thermal management.     

Hierarchical Ordered Dual‐Mesoporous Polypyrrole/Graphene Nanosheets as Bi‐Functional Active Materials for High‐Performance Planar Integrated System of Micro‐Supercapacitor and Gas Sensor

Planar integrated systems of micro‐supercapacitors (MSCs) and sensors are of profound importance for 3C electronics, but usually appear poor in compatibility due to the complex connections of device units with multiple mono‐functional materials. Herein, 2D hierarchical ordered dual‐mesoporous polypyrrole/graphene (DM‐PG) nanosheets are developed as bi‐functional active materials for a novel prototype planar integrated system of MSC and NH₃ sensor. Owing to effective coupling of conductive graphene and high‐sensitive pseudocapacitive polypyrrole, well‐defined dual‐mesopores of ≈7 and ≈18 nm, hierarchical mesoporous network, and large surface area of 112 m² g^?1, the resultant DM‐PG nanosheets exhibit extraordinary sensing response to NH₃ as low as 200 ppb, exceptional selectivity toward NH₃ that is much higher than other volatile organic compounds, and outstanding capacitance of 376 F g^?1 at 1 mV s^?1 for supercapacitors, simultaneously surpassing single‐mesoporous and non‐mesoporous counterparts. Importantly, the bi‐functional DM‐PG‐based MSC‐sensor integrated system represents rapid and stable response exposed to 10–40 ppm of NH₃ after only charging for 100 s, remarkable sensitivity of NH₃ detection that is close to DM‐PG‐based MSC‐free sensor, impressive flexibility with ≈82% of initial response value even at 180°, and enhanced overall compatibility, thereby holding great promise for ultrathin, miniaturized, body‐attachable, and portable detection of NH₃.     

High‐Temperature BiScO3‐PbTiO3 Piezoelectric Vibration Energy Harvester

Conventionally, effective mechanical vibration energy harvesting is based on (Pb,Zr)TiO₃ (PZT) ceramics, poly(vinylidene fluoride) (PVDF) polymers or PVDF/PZT or other piezoelectric composite materials, and their working temperature is normally limited to room temperature (R‐T) or below 150 °C. Here, bismuth scandium lead titanate (BiScO₃‐PbTiO₃, abbreviated as BSPT) ceramic is reported which has a high Curie temperature point around 450 °C and its application for high‐temperature (H‐T) vibration energy harvesting. Experimental results show that it exhibits an excellent H‐T piezoelectricity, converting mechanical vibration energy into electric power effectively in a wide temperature range from R‐T till 250 °C. This research shows the BSPT piezoelectric energy harvester having the potential application for self‐power source of wireless sensor network system in high temperature circumstance.     

Flexible and Waterproof Resistive Random‐Access Memory Based on Nitrocellulose for Skin‐Attachable Wearable Devices

Memory for skin‐attachable wearable devices for healthcare monitoring must meet a number of requirements, including flexibility and stability in external environments. Among various memory technologies, organic‐based resistive random‐access memory (RRAM) devices are an attractive candidate for skin‐attachable wearable devices due to the high flexibility of organic materials. However, organic‐based RRAMs are particularly vulnerable to external moisture, making them difficult to apply as skin‐attachable wearable devices. In this research, RRAMs are fabricated that meet the requirements for skin‐attachable wearable devices using a novel organic material, nitrocellulose (NC), which is biocompatible with high water‐resistance and high flexibility. The fabricated NC‐based RRAMs show a stable bipolar resistive switching characteristic. In addition, the formation of a native Al oxide between Al and NC is verified, which is the source of the bipolar switching characteristic of NC‐based RRAMs. Furthermore, electrical and chemical analysis is conducted after dipping and submersion into various solutions as well as deionized water to confirm the water‐resistance of the NC‐based RRAMs. Finally, it is also confirmed that NC‐based RRAMs are suitable for use in skin‐attachable wearable devices through a flexibility test. In conclusion, this study suggests that NC‐based RRAMs can be applied in skin‐attachable wearable devices, simplifying healthcare in the future.     

Swelling Behavior of Multiresponsive Poly(methacrylic acid)‐block‐‐poly(N‐isopropylacrylamide) Brushes Synthesized Using Surface‐Initiated Photoiniferter‐Mediated Photopolymerization

Surface‐initiated photoiniferter‐mediated photopolymerization (SI‐PMP) in presence of tetraethylthiuram disulfide is used to directly synthesize surface‐grafted poly(methacrylic acid)‐block‐poly(N‐isopropylacrylamide) (PMAA‐b‐PNIPAM) layers. The response of these PMAA‐b‐PNIPAM bi‐level brushes to changes in pH, temperature and ionic strength is investigated by using in‐situ multi‐angle ellipsometry to measure changes in solvated layer thickness. As expected for a block copolymer architecture, PMAA blocks swell as pH is increased, with the maximum change in the thickness occurring near pH = 5, and PNIPAM blocks exhibit lower critical solution temperature (LCST) behavior, marked by a broad transition between swollen and collapsed states. The response of the bi‐level brushes to changes in added salt at constant pH is complex, as the swelling behaviors of both the weak polyelectrolyte, PMAA, and thermoresponsive PNIPAM are affected by changes in ionic strength. This work demonstrates not only the robustness of SI‐PMP for making novel, bi‐level stimuli‐responsive brushes, but also the complex links between synthesis, structure, and response of these materials.     

Thermally Stable,Biocompatible, and Flexible Organic Field‐Effect Transistors and Their Application in Temperature Sensing Arrays for Artificial Skin

Application of degradable organic electronics based on biomaterials, such as polylactic‐co‐glycolic acid and polylactide (PLA), is severely limited by their low thermal stability. Here, a highly thermally stable organic transistor is demonstrated by applying a three‐arm stereocomplex PLA (tascPLA) as dielectric and substrate materials. The resulting flexible transistors are stable up to 200 °C, while devices based on traditional PLA are damaged at 100 °C. Furthermore, charge‐ trapping effect induced by polar groups of the dielectric is also utilized to significantly enhance the temperature sensitivity of the electronic devices. Skin‐like temperature sensor array is successfully demonstrated based on such transistors, which also exhibited good biocompatibility in cytotoxicity measurement. By presenting combined advantages of transparency, flexibility, thermal stability, temperature sensitivity, degradability, and biocompatibility, these organic transistors thus possess a broad applicability such as environment friendly electronics, implantable medical devices, and artificial skin.     

Low‐temperature flexible Ti/TiO2 photoanode for dye‐sensitized solar cells with binder‐free TiO2 paste

An energy‐economical dye‐sensitized solar cell (DSSC) with highly flexible Ti/TiO₂ photoanode was developed through a low‐temperature process, using a binder‐free TiO₂ paste. Ti foils, coated with the binder‐free TiO₂ films were annealed at various temperature. Scanning electron microscopic (SEM) images of the films show uniform, mesoporous and crack‐free surface morphologies as well as interpenetrated TiO₂ network. DSSCs with binder‐free TiO₂ films annealed at 450, 350, 250 and 120°C show solar‐to‐electricity conversion efficiencies (η) of 4.33, 4.34, 3.72 and 3.40%, respectively, which are comparable to the efficiency of 4.56% obtained by using a paste with binder and annealing it at 450°C; this observation demonstrates the benefits of a binder‐free TiO₂ paste for the fabrication of energy‐fugal DSSCs. On the other hand, when organic binder was used in the TiO₂ paste for film preparation, a drastic deterioration in the cell performance with decreasing annealing temperature is noticed. Laser‐induced photo‐voltage transient technique is used to estimate the electron lifetime in various Ti/TiO₂ films. Electrochemical impedance spectroscopic (EIS) analysis shows that the lower the annealing temperature of the TiO₂ coated Ti foil, the larger the charge transfer resistance at the TiO₂/dye/electrolyte interface (R_ct2). Copyright © 2011 John Wiley & Sons, Ltd.     

High‐κ Solid‐Gate Transistor Configured Graphene Biosensor with Fully Integrated Structure and Enhanced Sensitivity

A fully integrated graphene field‐effect transistor (GFET) nanosensor utilizing a novel high‐κ solid‐gating geometry for a practical biosensor with enhanced sensitivity is presented. Herein, an “in plane” gate supplying electrical field through a 30 nm HfO₂ dielectric layer is employed to eliminate the cumbrous external wire electrode in conventional liquid‐gate GFET nanosensors that undesirably limits the device potential in on‐site sensing applications. In addition to the advantage in the device integration degree, the transconductance level is found to be increased by about 50% over liquid‐gate GFET devices in aqueous‐media, thereby improves the sensitivity performance in sensor applications. As the first demonstration of biosensing applications, a small‐molecule antibiotic, kanamycin A, is detected by means of an aptameric competitive affinity principle. It is experimentally shown that the label‐free and specific quantification of kanamycin A with a concentration resolution at 11.5 × 10^?9 m is achievable through a single direct observation of the 200 s fast bioassay without any further noise canceling. These results demonstrate the utility and practicability of the new devices in label‐free biosensing as a novel analytical tool, and potentially hold great promise in other significant biomedical applications.     

Ultra‐Adaptable and Wearable Photonic Skin Based on a Shape‐Memory,Responsive Cellulose Derivative

Photonic skins enable a direct and intuitive visualization of various physical and mechanical stimuli with eye‐readable colorations by intimately laminating to target substrates. Their development is still at infancy compared to that of electronic skins. Here, an ultra‐adaptable, large‐area (10 × 10 cm²), multipixel (14 × 14) photonic skin based on a naturally abundant and sustainable biopolymer of a shape‐memory, responsive multiphase cellulose derivative is presented. The wearable, multipixel photonic skin mainly consists of a photonic sensor made of mesophase cholesteric hydroxypropyl cellulose and an ultra‐adaptable adhesive layer made of amorphous hydroxypropyl cellulose. It is demonstrated that with multilayered flexible architectures, the multiphase cellulose derivative–based integrated photonic skin can not only strongly couple to a wide range of biological and engineered surfaces, with a maximum of ≈180 times higher adhesion strengths compared to those of the polydimethylsiloxane adhesive, but also directly convert spatiotemporal stimuli into visible color alterations in the large‐area, multipixel array. These colorations can be simply converted into 3D strain mapping data with digital camera imaging.     

Ultrathin,Organic, Semiconductor/Polymer Blends by Scanning Corona‐Discharge Coating for High‐Performance Organic Thin‐Film Transistors

A new thin‐film coating process, scanning corona‐discharge coating (SCDC), to fabricate ultrathin tri‐isopropylsilylethynyl pentacene (TIPS‐PEN)/amorphous‐polymer blend layers suitable for high‐performance, bottom‐gate, organic thin‐film transistors (OTFTs) is described. The method is based on utilizing the electrodynamic flow of gas molecules that are corona‐discharged at a sharp metallic tip under a high voltage and subsequently directed towards a bottom electrode. With the static movement of the bottom electrode, on which a blend solution of TIPS‐PEN and an amorphous polymer is deposited, SCDC provides an efficient route to produce uniform blend films with thicknesses of less than one hundred nanometers, in which the TIPS‐PEN and the amorphous polymer are vertically phase‐separated into a bilayered structure with a single‐crystalline nature of the TIPS‐PEN. A bottom‐gate field‐effect transistor with a blend layer of TIPS‐PEN/polystyrene (PS) (90/10 wt%) operated at ambient conditions, for example, indeed exhibits a highly reliable device performance with a field‐effect mobility of approximately 0.23 cm² V^?1 s^?1: two orders of magnitude greater than that of a spin‐coated blend film. SCDC also turns out to be applicable to other amorphous polymers, such as poly(α‐methyl styrene) and poly(methyl methacrylate) and, readily combined with the conventional transfer‐printing technique, gives rise to micropatterned arrays of TIPS‐PEN/polymer films.     

Flexible Near‐Infrared Plastic Phototransistors with Conjugated Polymer Gate‐Sensing Layers

Flexible near‐infrared (NIR) light‐sensing detectors are strongly required in the fast‐growing flexible electronics era, because they can serve as a vision system like eyes in various innovative applications including humanoid robots. Recently, keen interest has been paid to organic phototransistors due to their unique signal amplification and active matrix driving features over organic photodiodes. However, conventional NIR‐sensing organic phototransistors suffer from the limited use of organic materials because the channel layers play a dual role in both charge transport and sensing so that organic semiconducting materials with reasonably high charge mobility can be applied only. Here, it is demonstrated that a conjugated polymer, poly[{2,5‐bis‐(2‐ethylhexyl)‐3,6‐bis‐(thien‐2‐yl)‐pyrrolo[3,4‐c]pyrrole‐1,4‐diyl}‐co‐{2,2′‐(2,1,3‐benzothiadiazole)]‐5,5′‐diyl}] (PEHTPPD‐BT), which exhibits no transistor performance as a channel layer, can stably detect a NIR light (up to 1000 nm) as a gate‐sensing layer (GSL) when it is placed between gate‐insulating layers and gate electrodes. The flexible array (10 × 10) detectors with the PEHTPPD‐BT GSLs could effectively sense NIR light without visible light interference by applying visible light cut films.     

Low‐Temperature,Nontoxic Water‐Induced Metal‐Oxide Thin Films and Their Application in Thin‐Film Transistors

Here, a simple, nontoxic, and inexpensive “water‐inducement” technique for the fabrication of oxide thin films at low annealing temperatures is reported. For water‐induced (WI) precursor solution, the solvent is composed of water without additional organic additives and catalysts. The thermogravimetric analysis indicates that the annealing temperature can be lowered by prolonging the annealing time. A systematic study is carried out to reveal the annealing condition dependence on the performance of the thin‐film transistors (TFTs). The WI indium‐zinc oxide (IZO) TFT integrated on SiO₂ dielectric, annealed at 300 °C for 2 h, exhibits a saturation mobility of 3.35 cm² V^?1 s^?1 and an on‐to‐off current ratio of ≈10⁸. Interestingly, through prolonging the annealing time to 4 h, the electrical parameters of IZO TFTs annealed at 230 °C are comparable with the TFTs annealed at 300 °C. Finally, fully WI IZO TFT based on YO_x dielectric is integrated and investigated. This TFT device can be regarded as “green electronics” in a true sense, because no organic‐related additives are used during the whole device fabrication process. The as‐fabricated IZO/YO_x TFT exhibits excellent electron transport characteristics with low operating voltage (≈1.5 V), small subthreshold swing voltage of 65 mV dec^?1 and the mobility in excess of 25 cm² V^?1 s^?1.