A new type of electronic skin could allow robots, prosthetic devices, and wearable technologies to detect not only when they are touched, but also when an object is approaching. Researchers at Hanyang University in South Korea have developed a vertically integrated dual-gated tribotronic transistor that combines mechanical sensing with electrical signal amplification in a compact architecture. The device uses triboelectric charges—electrical charges generated when two materials contact and separate—to create a tunable response to touch, pressure, and proximity.
The technology addresses two persistent challenges in tribotronic sensing. Conventional tribotronic devices can be highly sensitive, but their response is often difficult to adjust after fabrication. They can also require relatively large areas or complicated layouts, making them difficult to integrate into dense, large-area sensor arrays. The Hanyang University design tackles both problems by placing two electrically functional gates into a vertical stack, allowing the sensing response to be controlled while reducing the footprint of each pixel.
At the heart of the device is an indium-tin-zinc-oxide, or ITZO, thin-film transistor. ITZO is an oxide semiconductor that can be fabricated on large-area substrates and is widely considered promising for transparent, flexible, and active-matrix electronics. Above the transistor, the researchers placed a dedicated gate insulator and a polydimethylsiloxane, or PDMS, triboelectric sensing layer. The PDMS layer acts as the upper gate, while a conventional lower gate controls the transistor’s baseline electrical state.
The sensing process begins with a charging step. A stainless-steel plate is brought into contact with the PDMS surface, causing charge to form at the interface through the triboelectric effect. When the plate is withdrawn, the separated charges generate an electrical potential on the PDMS layer. This potential functions as a top-gate voltage and suppresses the current flowing through the ITZO transistor. In this way, a mechanical event is converted directly into a measurable change in transistor current without requiring an external power source at the sensing interface.
The device can also detect an approaching object. As a charged plate or probe moves back toward the PDMS surface, the triboelectric potential gradually changes, and the transistor current begins to recover. The magnitude and evolution of this current change provide information about the object’s proximity. Unlike a simple on-or-off touch sensor, the transistor produces an analog response that can reflect how close an object is to the surface. This could be useful in robotic grippers, artificial fingertips, gesture-recognition systems, and wearable interfaces that need to respond before physical contact occurs.
The lower gate provides an additional layer of control. By changing the bottom-gate voltage, researchers can adjust the transistor’s baseline current and tune the sensitivity of the tribotronic response. Their measurements showed that sensitivity increased as the bottom-gate voltage rose. This electrical programmability could allow different regions of a future electronic skin to be configured for different tasks, such as detecting light contact in one area while measuring stronger pressure in another, without redesigning the sensing material itself.
Mechanical force also influenced the device’s performance. Increasing the contact pressure enlarged the effective contact area between the PDMS and the contacting object. A larger contact area generated more triboelectric charge, which in turn produced a stronger electrical response. This relationship between pressure, charge generation, and transistor current gives the architecture the potential to distinguish different levels of touch rather than merely identify contact. Such capability is essential for systems designed to recognize handling, gripping force, or human contact with greater precision.
In individual devices, the researchers recorded a response time of approximately 127 milliseconds and a recovery time of about 212 milliseconds during repeated contact and separation cycles. The transistor also maintained stable operation after 1,000 cycles, with no noticeable degradation reported. Although these results represent laboratory testing rather than a finished commercial product, the combination of tunable sensitivity, rapid response, and operational stability suggests that the architecture could be adapted for practical active-matrix sensing systems.
To demonstrate scalability, the team fabricated a 10-by-10 array containing 100 tribotronic transistor pixels. After the PDMS sensing layer was initially charged with a stainless-steel plate, the array responded to individual finger touches at the pixel level. The researchers also demonstrated proximity detection with a stainless-steel probe at distances of up to 500 micrometers. Because each pixel is connected to a transistor, the array can potentially be addressed and read electronically in a manner similar to display backplanes and other active-matrix technologies.
The researchers say the vertically integrated structure could provide a route toward electronic skin capable of sensing touch, pressure, and proximity within a dense, mechanically robust platform. Such systems may eventually help robots interact more safely with people, give prosthetic devices a more nuanced sense of their surroundings, and enable wearable electronics that respond to approaching objects or changing contact conditions. The study, published in Nano Energy, presents the device as a scalable foundation for programmable tribotronic sensor arrays and next-generation human–machine interfaces.
Subject of Research: Experimental study of a tribotronic transistor and active-matrix tactile and proximity sensing array.
Article Title: Vertically integrated dual-gated tribotronic transistor for active-matrix tactile and proximity sensing
Web References: https://doi.org/10.1016/j.nanoen.2026.111945
References: 10.1016/j.nanoen.2026.111945
Image Credits: Associate Professor Jaekyun Kim, Hanyang University
Keywords
Tribotronic transistor, electronic skin, tactile sensing, proximity sensing, triboelectric nanogenerator, wearable electronics, flexible electronics, ITZO thin-film transistor, active-matrix sensor, human–machine interfaces
