Advanced Multiparallel-Connected Piezoresistive Physical Sensors: Elevating Performance Reliability of Flexible Strain and Pressure Sensors.

A physical sensor with a sensing medium comprising multiparallel-connected (MPC) piezoresistive pathways in both the vertical and horizontal directions was developed to achieve improved sensing performance. The MPC sensing medium reduces the total resistance and offsets noise, offering enhanced signal stability and device reliability and providing a high-performance sensing platform. The signal change and gauge factor (GF) of the 3PW-5L strain sensor (comprising three lines and five layers of piezoresistive pathways horizontally and vertically, respectively) were, respectively, 5.9 and 4.7 times higher than those of the 1PW-1L sensor composed of a monosensing pathway; the hysteresis of the detected signal was also significantly reduced. The linearity of the detected signal increased from 0.912 for 1PW-1L to 0.995 for 3PW-5L, indicating a greater sensing reliability. The direction of the applied tensile strain was successfully detected using the MPC sensing medium with an orthogonal configuration. The MPC piezoresistive sensor composing vertically stacked piezoresistive pathways demonstrated excellent performance as a pressure sensor; the 3PW-5L pressure sensor afforded a GF of 0.121 ± 0.002 kPa-1 with a linearity of 0.998 under an applied pressure ≥16.4 kPa. The MPC piezoresistive physical sensor offers a superior sensing performance and should contribute to the future development of wearable sensors and electronic devices.

Low-Temperature, Universal Synthetic Route for Mesoporous Metal Oxides by Exploiting Synergistic Effect of Thermal Activation and Plasma.

Mesoporous metal oxides exhibit excellent physicochemical properties and are widely used in various fields, including energy storage/conversion, catalysis, and sensors. Although several soft-template approaches are reported, high-temperature calcination for both metal oxide formation and template removal is necessary, which limits direct synthesis on a plastic substrate for flexible devices. Here, a universal synthetic approach that combines thermal activation and oxygen plasma to synthesize diverse mesoporous metal oxides (V2O5, V6O13, TiO2, Nb2O5, WO3, and MoO3) at low temperatures (150-200 °C), which can be applicable to a flexible polymeric substrate is introduced. As a demonstration, a flexible micro-supercapacitor is fabricated by directly synthesizing mesoporous V2O5 on an indium-tin oxide-coated colorless polyimide film. The energy storage performance is well maintained under severe bending conditions.

Dissecting the Interplay between Organic Charge-Modulated Field-Effect Transistors and Field-Effect Transistors through Interface Control Engineering.

Organic charge-modulated field-effect transistors (OCMFETs) have garnered significant interest as sensing platforms for diverse applications that include biomaterials and chemical sensors owing to their distinct operational principles. This study aims to improve the understanding of driving mechanisms in OCMFETs and optimize their device performance by investigating the correlation between organic field-effect transistors (OFETs) and OCMFETs. By introducing self-assembled monolayers (SAMs) with different functional groups on the AlOx gate dielectric surface, we explored the impact of the surface characteristics on the electrical behavior of both devices. Our results indicate that the dipole moment of the dielectric surface is a critical control variable in the performance correlation between OFET and OCMFET devices, as it directly impacts the generation of the induced floating gate voltage through the control gate voltage. The insights obtained from this study contribute to the understanding of the factors affecting OCMFET performance and emphasize their potential as platforms for diverse sensing systems.

Photopatternable poly(4-styrene sulfonic acid)-wrapped MWNT thin-film source/drain electrodes for use in organic field-effect transistors.

We describe the cross-linking of poly(4-styrene-sulfonic acid) (PSS) by exposure to ultraviolet (UV) light (λ = 255 nm) under a vacuum. Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) showed that the photo-crosslinking of PSS resulted from coupling between radicals that were generated in the polymer chains by UV excitation. The photo-cross-linkable characteristics of PSS were employed to fabricate solution-processable, photopatternable, and conductive PSS-wrapped multiwalled carbon nanotube (MWNT) composite thin films by wrapping MWNTs with PSS in water. During photo-cross-linking, the work function of the PSS-wrapped MWNTs decreased from 4.83 to 4.53 eV following cleavage of a significant number of sulfonic acid groups. Despite the decreased work function of the PSS-wrapped MWNTs, the photopatterned PSS-wrapped MWNTs produced good source/drain electrodes for OFETs, yielding a mobility (0.134 ± 0.056 cm²/(V s)) for the TIPS-PEN field-effect transistors fabricated using PSS-wrapped MWNTs as source/drain electrodes that was higher than the mobility of gold-based transistors (0.011 ± 0.004 cm²/(V s)).

Dependence of pentacene crystal growth on dielectric roughness for fabrication of flexible field-effect transistors.

The dependence of pentacene nanostructures on gate dielectric surfaces were investigated for flexible organic field-effect transistor (OFET) applications. Two bilayer types of polymer/aluminum oxide (Al(2)O(3)) gate dielectrics were fabricated on commercial Al foils laminated onto a polymer back plate. Some Al foils were directly used as gate electrodes, and others were smoothly polished by an electrolytic etching. These Al surfaces were then anodized and coated with poly(alpha-methyl styrene) (PAMS). For PAMS/Al(2)O(3) dielectrics onto etched Al foils, surface roughness up to approximately 1 nm could be reached, although isolated dimples with a lateral diameter of several micrometers were still present. On PAMS/Al(2)O(3) dielectrics (surface roughness >40 nm) containing mechanical grooves of Al foil, average hole mobility (mu(FET)) of 50 nm thick pentacene-FETs under the low operating voltages (|V| < 6 V) was approximately 0.15 cm(2) V(-1) s(-1). In contrast, pentacene-FETs employing the etched Al gates exhibited mu(FET) of approximately 0.39 cm(2) V(-1) s(-1), which was comparable to that of reference samples with PAMS/Al(2)O(3) dielectrics onto flat sputtered Al gates. Conducting-probe atomic force microscopy and two-dimensional X-ray diffraction of pentacene films with various thicknesses revealed different out-of-plane and in-plane crystal orderings of pentacene, depending on the surface roughness of the gate dielectrics.

Solution-processed flexible ZnO transparent thin-film transistors with a polymer gate dielectric fabricated by microwave heating.

We report the development of solution-processed zinc oxide (ZnO) transparent thin-film transistors (TFTs) with a poly(2-hydroxyethyl methacrylate) (PHEMA) gate dielectric on a plastic substrate. The ZnO nanorod film active layer, prepared by microwave heating, showed a highly uniform and densely packed array of large crystal size (58 nm) in the [002] direction of ZnO nanorods on the plasma-treated PHEMA. The flexible ZnO TFTs with the plasma-treated PHEMA gate dielectric exhibited an electron mobility of 1.1 cm(2) V(-1) s(-1), which was higher by a factor of approximately 8.5 than that of ZnO TFTs based on the bare PHEMA gate dielectric.

Photopatternable source/drain electrodes using multiwalled carbon nanotube/polymer nanocomposites for organic field-effect transistors.

We fabricated photopatternable and conductive polymer/multiwalled carbon nanotube (MWNT) composites by dispersing MWNTs with poly(4-styrenesulfonic acid) (PSS) and poly(acrylic acid) (PAA) in water. PAA enables photo-cross-linking in the composite by adding ammonium dichromate, and PSS assists the dispersion of MWNTs in the composites, leading to higher conductivity. Composite films of PAA/PSS-MWNTs were characterized by conductivities of 1.4-210 S/cm and a work function of 4.46 eV, which could be increased to 4.76 eV during UV photo-cross-linking. By using PAA/PSS-MWNT composites as source/drain electrodes, 6,13-bis(triisopropylsilylethynyl)pentacene field-effect transistors (FET) exhibited a field-effect mobility of 0.101 +/- 0.034 cm(2)/(V s), which is 9 times higher than that of FETs fabricated with gold as source/drain electrodes (0.012 +/- 0.003 cm(2)/(V s)).

Preparation and in vivo evaluation of piroxicam-loaded gelatin microcapsule by spray drying technique.

To develop a piroxicam-loaded gelatin microcapsule with enhanced bioavailability, a gelatin microcapsule encapsulated ethanol and piroxicam has been formulated by using gelatin as a water-soluble polymer shell. The aqueous solubility and bioavailability of piroxicam in piroxicam-loaded microcapsule in rats were then evaluated compared to piroxicam powder. The piroxicam-loaded gelatin microcapsule spherical in shape with smooth surface showed the geometric mean diameter of about 19 microm. It had the piroxicam solubility of about 1.87 mg/ml and the amount of ethanol of about 4.37 microg/mg. Furthermore, it gave significantly higher total plasma concentrations, Cmax and area under the blood concentration-time curve (AUC) of piroxicam in rats than did piroxicam powder, indicating that the drug from gelatin microcapsule could be more orally absorbed in rats. In particular, the AUC of piroxicam in gelatin microcapsule was significantly about 2 fold increased compared to piroxicam powder. This enhanced oral relative bioavailability of piroxicam in gelatin microcapsule was contributed by the marked increase in the absorption rate of piroxicam due to the improved solubility of piroxicam. Thus, the piroxicam-loaded gelatin microcapsule developed using spray-drying technique with gelatin, sodium lauryl sulfate and ethanol would be useful to deliver piroxicam in a pattern that allows fast absorption in the initial phase, leading to better absorption.