Researchers at Washington State University have developed a 3D-printed electronic skin that senses pressure and temperature at ten times the resolution of commercial glove sensors. The customizable modular e-skin conforms to prosthetic limbs to give amputees tactile feedback without high production costs.
Across the United States, approximately 1.9 million people live without a limb, a population projected to double by 2050 largely due to the increasing frequency of diabetes, according to the National Library of Medicine. While advanced prosthetic limbs have steadily improved in strength and dexterity over the years, restoring the sense of touch has proven exceptionally difficult. Without tactile feedback, users must rely almost entirely on sight to gauge grip strength or prevent objects from slipping.
Engineers at Washington State University aim to close that gap. The team developed a customizable electronic skin that combines high-resolution pressure and temperature sensing, detailed in research published in the journal Cell Reports Physical Science.
Overcoming the Limits of Commercial E-Skins
Existing electronic skins force a difficult trade-off between mechanical reliability and user comfort. High-density sensing arrays are typically manufactured on flat surfaces using expensive clean-room processes, making them difficult to adapt to the complex, curved shapes of a prosthetic hand or arm. When manufacturers attempt to custom-shape these skins, their sensing ability often degrades, and the massive data loads generated by dense sensor arrays create real-time processing lag.
“Often these devices are forced to compromise between comfort and mechanical reliability.”
Hongyi Shen, graduate student in the School of Mechanical and Materials Engineering at Washington State University
The Washington State University team bypassed these constraints by designing a modular system that can detect pressure and temperature with roughly ten times the spatial resolution of commercial glove-based sensors.
Scan-Model-Print Manufacturing and Lego-Like Modules
To achieve seamless coverage across freeform geometries, the research team implemented a manufacturing strategy they call scan-model-print.
A structured-light 3D scanner captures the geometry of the prosthetic component, allowing software to map sensor layouts directly onto the scanned shape before custom structural layers are produced using stereolithography 3D printing.
“The scanner basically scans the prosthetic and then, based on the geometry, we map our sensors as a multimodal sensing system with that geometry.”
Kaiyan Qiu, assistant professor in the School of Mechanical and Materials Engineering at Washington State University
Each sensor module is built as a multilayer sandwich less than two millimeters thick. Inside, piezoresistive film handles pressure-sensing matrices alongside miniature thermistors for temperature. Rather than relying on permanent adhesives, individual modules snap together like Lego blocks, simplifying assembly, reconfiguration, and the replacement of damaged sections.
Neural Networks and Real-Time Calibration
Managing the data output of high-density sensor arrays presents a formidable hurdle.
Beyond measuring force, the e-skin distinguishes surface textures by monitoring tiny vibrations generated as a finger slides across an object. Temperature sensing adds another layer of feedback, enabling the system to differentiate materials based on how quickly heat flows between the sensor and the object.
Toward Bionic Integration and Affordability
The electronic skin currently functions as the sensing half of a complete bionic system. To restore actual sensation to an amputee, the electrical signals must be converted into nerve stimulation. The research team is currently developing an actuator designed to convert the e-skin data into stimulation for nearby nerves, allowing users to perceive what their prosthetic touches through nerve signals sent to the brain.
“This approach democratizes the production of medical-grade e-skins, making advanced tactile feedback viable for widespread clinical adoption.”
Hongyi Shen, graduate student at Washington State University
The team has already submitted an invention disclosure for a provisional patent through the Washington State University Office of Research Innovation and Entrepreneurship.
