Switchable analog, digital organic transistor Researchers from Pusan National University developed a stretchable organic electrochemical transistor (OECT) that can be reprogrammed to serve different purposes. The device operates by moving ions through the conducting polymer PEDOT:PSS, which was modified with additives to improve electrical conductivity and improve its ability to stretch without degrading. Changing the concentration of sodium chloride in the electrolyte alters how ions move through the transistor. High salt concentrations enabled rapid ON/OFF gating for digital logic computations, while lower salt concentrations produced an analog memory-like behavior that can act as an artificial synapse. The switching is reversible and is accompanied by the device changing color. “The proposed platform is suitable for smart electronic skin, wearable health monitors, and soft bioelectronic implants, where a single stretchable device can both process and store physiological signals without added circuitry,” said Hyunseok Shim, an assistant professor in the School of Electronics and Electrical Engineering at Pusan National University, in a statement. “In the longer term, this work could lead to autonomous personalized therapeutics, such as dynamic compression bandages and electronic skins that respond to injury in real time, all monitored at a glance through a visible color change.” As a proof of concept, the team built a wearable patch that senses inflammatory edema and skin temperature, then automatically tightens or loosens a compression band, reducing the risk of tissue damage. [1] Thread-based ICs Researchers at Tufts University designed thread-based integrated circuits that can bend, coil, and stretch for wearable electronics or textiles. The device uses thin threads coated with gold, to which flexible organic eutectogel-gated electrochemical transistors are attached. The deep eutectic solvents, or eutectogels, act as nonvolatile dielectrics that provide stable transistor performance without the need for encapsulation and avoid some of the challenges of hydrogels like drying out. “By moving electronics from planar patches to free-form threads, we have opened a path toward wearable bioelectronics that are more like fibers than hardware,” said Sameer Sonkusale, a professor in the School of Engineering at Tufts, in a press release. “They will be soft, stretchable and able to follow the body’s shape rather than forcing the body to accommodate the device. They could even potentially be used like sutures to monitor processes inside the body.” The researchers created several circuits to demonstrate the approach: a sensor signal amplifier, a wearable monitor that can be placed on the temple to detect blinking, and a device placed near the diaphragm to detect changes in breathing patterns and rates. “The technology platform is still in early stages,” added Wenxin Zeng, Ph.D. candidate in electrical engineering at Tufts, in a press release. “But we expect to improve the speed and precision of fabrication, and the ability of the thread-based integrated circuits to carry out more complex functions.” [2] Temporary e-tattoo electrodes Researchers from Penn State University developed a conductive ink that can be painted on the skin in various colors and patterns, creating temporary e-tattoos that act as electrodes to record electrical signals that indicate heart, muscle, and brain activity. The ink is made from several different types of polymers mixed with acidic additives into a water-based solution, with a glue-like consistency when wet. It can be pigmented with food dyes to paint electrodes with personalized designs and can dry onto skin in less than 10 minutes. A porous, silver textile is attached to the skin’s surface with a portion of the paint and then connected to a larger module that transmits signals using Bluetooth. The textile’s porous structure allows the electrodes to stretch to over 150% their original size without breaking. It also adheres better to skin, resulting in better conductivity particularly in the presence of hair or sweat, which can create challenges for typical electrodes. In tests, the device tracked ECG readings over the course of 12 hours, during exercise, and enabled a user to control a robot prosthetic using muscle signals. “Although we tested the daily use application over a 12-hour period, this is not the limit for these electrodes,” said Larry Cheng, professor of engineering science and mechanics at Penn State, in a press release. “The electrodes themselves can be washed away and easily reapplied. The big idea behind this is that in the future, you could potentially have a more expensive sensing module that remains separate from the system, but the electrodes themselves can be disposable. A single bottle of ink could provide enough material to paint multiple electrodes over the course of several days or a week.” The team plans to continue developing the electrodes to potentially enable more advanced health sensing of biomarkers like cortisol or glucose. [3] References [1] H. Kim, T. Kim, Y. Kim, et al. Fully Stretchable Ionically Tunable Organic Electrochemical Transistors for Wearable Adaptive Logic Bioelectronics. ACS Nano (2026) 20 (26): 18883–18899. https://doi.org/10.1021/acsnano.6c05309 [2] W. Zeng, R. E. Owyeung, N. I. Hossain, et al. Free-Form Three-Dimensional Integrated Circuits on a Thread Using Organic Eutectogel-Gated Electrochemical Transistors. ACS Appl. Mater. Interfaces (2026) 18 (21): 30211–30226. https://doi.org/10.1021/acsami.5c25103 [3] W. Zhang, X. Xin, Y. Wang, et al. Paintable on-skin dry electrodes with robust skin and device connection for wireless sensing and human–machine interfaces, Proc. Natl. Acad. Sci. U.S.A. 123 (29) e2615835123, (2026). https://doi.org/10.1073/pnas.2615835123 The post Research Bits: Aug. 4 appeared first on Semiconductor Engineering.
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