Here we summarize recent progress in the development of electrolyte-gated transistors (EGTs) for organic and printed electronics. EGTs employ a high capacitance electrolyte as the gate insulator; the high capacitance increases drive current, lowers operating voltages, and enables new transistor architectures. Although the use of electrolytes in electronics is an old concept going back to the early days of the silicon transistor, new printable, fast-response polymer electrolytes are expanding the potential applications of EGTs in flexible, printed digital circuits, rollable displays, and conformal bioelectronic sensors. This report introduces the structure and operation mechanisms of EGTs and reviews key developments in electrolyte materials for use in printed electronics. The bulk of the article is devoted to electrical characterization of EGTs and emerging applications.

Printed, flexible sub-2 V ZnO electrolyte gated transistors (EGTs) are demonstrated. ZnO EGTs with high-capacitance ion-gel gate insulators are printed on a kapton substrate and the devices exhibit high electron mobility (1.61 cm(-2) V(-1) s(-1) ), low operation voltage (<2 V), and good electrical/mechanical stabilities.

We report performance optimization and stability analysis of aerosol-jet-printed electrolyte-gated transistors (EGTs) based on the polymer semiconductor poly(3-hexylthiophene) (P3HT). EGTs were optimized with respect to printed P3HT thickness and the completed device annealing temperature. EGTs with relatively thin P3HT films (∼50 nm) annealed at 120 °C have the best performance and display an unusual combination of metrics including sub-1-V operation, ON/OFF current ratios of 10(6), OFF currents of <10(-10) A (<10(-6) A cm(-2)), saturation hole mobilities of 1.3 cm(2) V(-1) s(-1), threshold voltages of -0.3 V, and subthreshold swings of 70 mV decade(-1). Furthermore, optimized EGTs printed on polyester substrates are extremely robust to bias stress and repeated mechanical bending strain. Collectively, the results suggest that optimized P3HT-based EGTs are promising devices for printed, flexible electronics.

We investigated the optical properties of a dielectric-metal-dielectric multilayer for the transparent top cathode in top-emitting organic light emitting diodes (TOLEDs). The optical transmittance of the metal layer was enhanced by depositing a dielectric material which had a high refraction index n below and above the metal (Ag) layer. Due to multiple reflections and interferences, the Ag layer sandwiched between dielectric materials with a high value of n can show improved transmittance. Because the WO 3 had a high value of n (>2.0), a thin WO 3 layer could fulfill the optimum zero-reflection condition with an Ag metal layer. Thus, a WO 3 /Ag/WO 3 multilayer should have high transmittance with a low sheet resistance. The optimum thicknesses of both Ag and WO 3 to obtain the best transmittance value were determined by theoretical calculation, and they agreed well with the experimental results. The best results were obtained for the thermally evaporated WO 3 (300 Å)/Ag (120 Å)/WO 3 (300 Å) structure, a high transmittance of ∼93.5% and a low sheet resistance about ∼7.22 ohm/sq were obtained. When the top Al cathode was replaced with the WO 3 /Ag/WO 3 multilayer, the maximum luminance value (J = 220 mA/cm 2 ) increased from 8400 to 11700 cd/m 2 , and the power efficiency increased about 26%. To improve the electron injection efficiency at the cathode region, a 20-Å thick Al layer was introduced as an electron injection interlayer between the organic materials and the WO 3 /Ag/WO 3 cathode. Using the Al interlayer decreased the operation voltage at J = 10 mA/cm 2 by 6.9 V. Thus, a WO 3 /Ag/WO 3 with an Al interlayer could promote the transparency of the top cathode and lower the electron injection barrier, enhancing the electroluminescent properties of TOLED.

This study aimed to investigate the anti-inflammatory, anti-arthritic and immuno-regulatory effects of electro-acupuncture (EA) at ST36 on Collagen-induced arthritis (CIA) in mice. Male DBA/1J mice were divided into five groups: Normal, Control, NR (needle retention), EAI and EAII. All mice except those in the normal group were immunized with Collagen II for arthritis induction. Acupuncture needles were inserted into mice ST36 and electrical currents at a frequency of 2 Hz in a continuous rectangular wave form were conducted through the needles for 15 min, 3 times a week. EA treatments were administered for 5 weeks in the EAI group and for 9 weeks in the EAII group. The mice in the NR group were acupunctured in the same manner as the EA groups and the needles were retained for 15 min without electrical stimulation. CIA incidence analysis, ELISA, histological analysis and FACS analysis were performed to evaluate the effect of EA on CIA. EA at ST36 significantly reduced CIA incidence, IL-6, TNF-a, INF-γ, collagen II antibody, IgG and IgM levels in CIA mice serum and prevented knee joint destruction. EA at ST36 also reduced CD69+/CD3e+ cells and CD11a+/CD19+ cells in CIA mice lymph nodes, and CD11b+/Gr1+ cells in CIA mice knee joints. The ratios of CD3e+ cells to CD19+ cells, and CD8+ cells to CD4+ cells were maintained closer to the normal range in the EA groups as compared with the control group or the NR group. EAII was more effective than EAI throughout all the measurements. The NR was effective as well, though less effective than EA. EA at ST36 may have an anti-inflammatory, anti-arthritic and immuno-regulatory effects on CIA in mice. The effectiveness is stronger when EA starts earlier and is applied longer. Needle retention without electrical stimulation may be effective on CIA as well, however less effective than EA. Electrical stimulation and acupoint ST36 may have synergistic effects on CIA.