IN Brief:
- Hanyang University researchers have developed a vertically integrated dual-gated tribotronic transistor for tactile and proximity sensing.
- A PDMS triboelectric layer acts as the upper sensing gate above an ITZO thin-film transistor.
- Electrical control through the lower gate adjusts sensitivity while the vertical structure reduces individual sensor area.
Hanyang University ERICA researchers have developed a vertically integrated dual-gated tribotronic transistor intended to improve the controllability and integration density of tactile and proximity sensors used in electronic-skin systems.
The device combines a polydimethylsiloxane, or PDMS, triboelectric sensing layer with an indium-tin-zinc-oxide thin-film transistor. The PDMS layer functions as a triboelectric upper gate, while a separately biased lower gate controls the ITZO transistor, allowing mechanical sensing and electrical adjustment to influence the same channel through different mechanisms.
Triboelectric sensing relies on charge generated when materials make contact and separate. That principle is attractive for artificial skin because mechanical interaction can generate the sensing signal directly, potentially reducing the need for a separate powered transducer at every sensing point. The difficulty is turning that response into an architecture that can be tuned and repeated across large arrays.
The Hanyang design addresses part of that problem through vertical integration. Placing the triboelectric sensing layer directly above the transistor reduces the lateral area required for each sensing element. That becomes important once a system moves from a single demonstrator to an active matrix containing hundreds or thousands of independently addressed pixels.
The lower gate adds another level of control. Its bias establishes the baseline electrical condition of the ITZO transistor, while charge generated at the PDMS layer modulates the channel through the upper gate. Changing the electrical bias therefore adjusts how strongly the transistor responds to a given mechanical interaction.
That is useful because tactile sensors do not necessarily need the same sensitivity in every application. A robotic gripper handling delicate components may need to respond to relatively small forces, while another surface may need to ignore minor contact and react only when a larger mechanical load is applied. Electrical tunability gives the sensing system a route to modify behaviour without changing the mechanical structure of every pixel.
The device can also distinguish proximity after triboelectric charging has occurred. When a contacting object touches the PDMS layer, charge is generated at the interface. As the object is withdrawn, the resulting potential changes the transistor current through the upper gate. Bringing the object closer again alters that potential and produces a corresponding electrical response before renewed contact occurs.
The same device can therefore provide information about both physical touch and the approach of an object. For robotics, that distinction may be valuable because a manipulator can begin responding before contact rather than relying entirely on force measurements taken after a surface has already been touched.
The researchers also observed a stronger response as contact pressure increased. Greater pressure produces a larger effective contact area between the triboelectric surfaces, increasing the generated charge and changing the transistor response accordingly. That gives the architecture a route to distinguish different levels of mechanical interaction rather than operating as a simple binary touch detector.
Large-area electronic skin presents wider manufacturing problems beyond individual sensor performance. Pixel-to-pixel uniformity, flexible interconnect, environmental protection, mechanical fatigue, and reliable active-matrix addressing all become important once an array is repeatedly bent, touched, or integrated over a curved surface.
Thin-film transistors offer an established route to active-matrix addressing, which is why combining the sensing mechanism directly with an ITZO TFT is significant. The closer the tactile element can be integrated with the switching transistor, the less peripheral circuitry and surface area are needed for each pixel.
The work was first published online in April and appeared in Volume 153 of Nano Energy in June. Its contribution lies in the device architecture rather than a finished robotic skin product: the researchers have demonstrated a way to separate electrical sensitivity control from mechanically generated triboelectric input while retaining a compact vertical structure.
Translating that structure into practical electronic skin will require much larger arrays, durable packaging, calibration, and evidence that device behaviour remains stable through repeated mechanical cycling. If those issues can be controlled, the dual-gate approach offers a useful route towards tactile surfaces whose sensitivity can be adjusted electronically rather than fixed permanently by the sensing material alone.
