UNIVERSITY PARK, Pa. — A research team, including Huanyu "Larry" Cheng , James L. Henderson Jr. Memorial Associate Professor of Engineering Science and Mechanics at Penn State, is using pressure sensors — tiny devices, roughly the size of a paperclip, that can measure the force applied over an area — to design a highly sensitive electronic "skin" to use alongside robots and prosthetic limbs.
Cheng is a corresponding author on a paper, recently published in Nano-Micro Letters , that introduces the improved pressure sensor design. The team's sensors can be assembled into an interconnected array, offering researchers and clinicians a wireless approach to recognizing spatial pressure distribution, hand gestures and even different types of food based off their weight and texture.
In the following Q&A, Cheng discussed pressure sensing technology and how his team's work could help robots accurately "feel" the sensation of touch.
Q: Why do current pressure-sensing technologies struggle to balance sensitivity and accuracy? How did you address these issues with your new design?
Cheng: It is still difficult for flexible pressure sensors to simultaneously achieve high precision and responsiveness to subtle pressures, despite extensive research and development. Conventional designs often provide abundant conductive networks, but their irregular arrangement weakens compressive strength, which limits detection range and long-term stability.
In this work, we designed a flexible pressure-sensing platform based on a material known as reduced graphene oxide aerogel (rGOA) — an incredibly lightweight, oxygen-rich material. Using freeze casting, a manufacturing technique that solidifies mixtures of liquids and solids into one material, we can form our sensors to have an anisotropic microstructure, meaning they have different mechanical strengths depending on the direction we apply stress.
With these adjustments, our sensors can simultaneously achieve ultrahigh sensitivity, a broad pressure detection range and long-term stability. Although a single sensor is only about eight millimeters in size, they can each support about three ounces of force and reliably load and unload weight over 20,000 times. By assembling individual sensors into an interconnected array, we can effectively create an artificial "skin" capable of precisely measuring extremely subtle changes in pressure.
Q: How are the sensors built? How did you test their effectiveness?
Cheng: The pressure sensor was fabricated by sandwiching rGOA between a synthetic, plastic-like film stamped with interdigital electrodes — small measurement devices printed onto the material in silver ink — and a layer of thin, silicon-based polymer material. Sandwiching the materials together ensures stable electrical contact, mechanical robustness and flexibility for practical applications.
We tested our sensors by measuring the current response under a wide range of applied pressures, while also assessing frequency response and stability under a range of temperatures and humidities. Our sensors proved extremely sensitive, offering almost twice as much sensitivity as sensors manufactured with traditional structures. Additionally, the sensors exhibited incredibly fast response and recovery times, responding to pressure changes in just over 100 milliseconds, and recovering from responses in only 40 milliseconds — a process that other sensor options can take over 250 milliseconds to fully cycle through.
Q: What does the process of assembling the sensors into an "artificial skin" look like? What sorts of devices and applications could use such a skin?
Cheng: The sensors can be assembled into an array, collecting many individual measurements. Using a microcontroller, a tiny computer designed to execute a specific task, these pressure signals are collected, converted into digital values and visualized in real time. This allows the sensors to identify the position and magnitude of pressure caused by different objects, which can be helpful for prosthetics, robotic manipulation and battery health monitoring.
The sensors' flexibility, ultrahigh sensitivity and environmental stability let the arrays conform to complex surfaces for precise pressure mapping, a way to visualize how much pressure is between two surfaces. These capabilities open new possibilities in smart robotics, wearables and human-machine interfaces, enabling the detection of dynamic pressure changes from irregular objects or small volume shifts. One key application is early identification of battery swelling in electric vehicles — a common issue where rising internal pressure can cause irreparable damage to a battery.
Additionally, the sensors can identify object shapes or help robotic systems grasp fragile objects. When used alongside a robotic manipulator like a hand or a vice, the sensors can monitor pressure in real time and compare it with preset safety thresholds to prevent object damage. This force-feedback system allows the robot to accurately track hand movements and grasp delicate objects such as tofu, cotton and steamed buns, which could be a big step forward in effective human-machine interaction and interfacing.
Q: What's next for this work? Are there plans for commercialization in the future?
Cheng: We plan to reduce the sensor size and weight to enhance biocompatibility and stability in complex environments. Additional research could enable spatially programmable sensitivity — allowing a single sensor or array to simultaneously detect subtle pressures in one region and withstand large loads in another — while also integrating pressure, temperature or strain sensing within a single, comprehensive structure.
We believe these sensors have a strong potential for future real-world deployment and commercialization through integration with wearable devices and commercial robots. Arrays of these sensors could offer a low-cost and high-performance sensing solution, while remaining highly flexible and customizable.
Collaborator and funding details can be found in the paper . The team has filed a provisional patent for this technology.
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