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 When the plate is withdrawn, the separated charges generate an electrical potential on the PDMS layer.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

Pressure injuries, commonly known as bedsores, emerge when sustained mechanical stress compresses soft tissues for extended periods, leading to tissue damage and often debilitating consequences. Despite advances in healthcare, current monitoring solutions frequently lack the sensitivity, spatial coverage, and biomechanical insight necessary to preemptively identify injury risks. The interdisciplinary team behind this study designed and validated a soft magnetoelastic sensor array, uniquely capable of mapping complex force distributions over large, deformable surfaces, thereby addressing critical gaps in existing technologies.

At the heart of this magnetoelastic system lies a novel composite material that exhibits tunable magneto-mechanical coupling properties. The soft sensor array integrates magnetically responsive elastomers with embedded microstructured architectures, enabling it to detect subtle variations in both compressive (normal) forces and tangential (shear) forces that are typically challenging to quantify simultaneously. This dual sensitivity is crucial because shear stress is recognized as a major contributor to skin and tissue breakdown but remains elusive in routine clinical assessments.

The fabrication process involves precision layering of magnetoelastic polymers onto elastomeric substrates, yielding a conformable sensor platform that can drape across irregular skin contours without impeding natural movement or causing discomfort. The device operates by responding to mechanical deformation through alterations in local magnetic field patterns—which are then decoded via external magnetic field sensing to reconstruct distributed stress maps. This non-invasive and wireless reading capability adds significant value in clinical environments where sensor hygiene and patient mobility are paramount.

Extensive bench-top testing demonstrated the sensor’s high responsivity and fidelity in detecting pressure and shear forces over large areas analogous to human skin surfaces. The team highlighted their successful calibration protocol, which isolates normal from shear stress components by analyzing anisotropic magnetic responses under controlled loading conditions. This quantitative precision heralds a new era of biomechanical monitoring that transcends the limitations of piezoelectric or resistive sensors, which often compromise sensitivity for flexibility.

Further, the researchers carried out in vivo pilot studies, placing the sensor on at-risk anatomical locations prone to pressure injury, such as the sacrum and heels, in subjects simulating prolonged bed rest and varying postural adjustments. The sensor array adeptly captured dynamic force redistributions caused by shifting posture and movement, providing real-time feedback on stress hotspots well before visible skin damage manifested. Such proactive risk detection empowers caregivers with actionable data to intervene early, adjusting positioning or cushioning to mitigate injury.

This technology’s potential extends beyond healthcare settings. Its scalable, soft form factor and high-resolution sensing capabilities suggest applications in wearable human-machine interfaces, prosthetic limb feedback, and soft robotics, where nuanced force mapping is critical. The magnetoelastic approach also enables energy-efficient sensing without complex wiring, fostering designs for embeddable smart materials that can monitor mechanical integrity in a range of contexts.

One of the particularly notable technical triumphs of this work is the seamless integration of magnetic sensing principles with elastomeric material science. By leveraging magnetoelasticity—where mechanical deformation alters magnetic properties—the team bypassed traditional electronic sensor drawbacks such as electrical noise, fragility, and limited conformability. This hybridization elevates the sensor’s robustness and longevity, delivering reliable performance in demanding, real-world conditions.

Manufacturing scalability was another consideration addressed by the researchers. The fabrication methods are compatible with established roll-to-roll processing techniques, underpinning the potential for producing these sensors at low cost and high volumes. Such scalability is critical for widespread adoption in clinical and commercial markets, where cost barriers have historically constrained access to continuous biomechanical monitoring tools.

The underlying data processing algorithms developed in parallel with the hardware were equally sophisticated. Advanced signal processing and machine learning techniques enabled the system to translate complex magnetic field perturbations into intuitive stress maps. These computational models also incorporate calibration against individual patient characteristics or anatomical variability, highlighting a personalized medicine dimension to the sensor’s deployment.

Moreover, the research underscores the importance of monitoring shear forces alongside normal pressure, a factor often neglected in prevention strategies. This insight is significant because shear stress can exacerbate tissue deformation and ischemia, accelerating injury progression. The magnetoelastic sensor’s comprehensive stress profiling thus provides clinicians a more complete biomechanical picture, fostering targeted and effective interventions.

Ethical considerations concerning patient comfort, data privacy, and long-term wearability were also thoughtfully explored. The device’s soft, skin-compatible materials minimize irritation and allow for prolonged monitoring sessions. Wireless data transmission possibilities further reduce infection risks associated with wired sensors, aligning with hospital safety protocols and enhancing patient compliance.

Looking forward, the research team anticipates integrating their sensor technology into multifunctional platforms that combine temperature, humidity, and biochemical sensing for holistic wound management. Such integrated systems could transform care models, shifting from reactive treatment to proactive injury prevention through continuous multimodal monitoring.

In conclusion, this large-area soft magnetoelastic sensor represents a paradigm shift in the biomechanical monitoring of skin and tissue health. By delivering real-time, high-resolution maps of normal and shear stress distributions over anatomically relevant surfaces, it offers unprecedented capabilities for preventing pressure injuries, enhancing patient outcomes, and expanding functional sensing applications across medical and technological domains. The successful marriage of material innovation, sensor engineering, and computational analytics showcased in this study portends a future where smart, adaptable sensing interfaces seamlessly merge with the human body.

Subject of Research: Pressure injury prevention through advanced soft magnetoelastic sensing technology analyzing normal and shear stress distributions.

Article Title: Large-area and soft magnetoelastic sensing for normal and shear stress distribution toward pressure injury prevention.

Article References:
Liu, Z., Chen, Y., Guo, C. et al. Large-area and soft magnetoelastic sensing for normal and shear stress distribution toward pressure injury prevention. Nat Commun (2025). https://doi.org/10.1038/s41467-025-67146-0

Image Credits: AI Generated