More than two million people are living with limb loss in the USA, and that number is expected to rise. For the majority of these individuals, prosthetic limbs are an invaluable tool to help regain some quality of life. One challenge that has been difficult to overcome in the design of prostheses, however, is enabling sensation through these devices. Our sense of touch is an incredibly sensitive and complex biological process that involves the interplay of many neurons of different types – and replicating this process electronically excites and perplexes many scientists in the field of prosthetic engineering. Any sensors used in such an application must be sufficiently small and allow for the detection of different types of stimuli, such as heat and texture. Now a team from the University of Texas at Dallas has dreamed up a design for electronic “whiskers” that could dramatically improve prosthetic design going forward.
The inspiration for the electronic whiskers, or “e-whiskers,” came from seals, which use their whiskers to sense exquisite detail about their environment. The team used a shape-memory polymer, which is usually stiff at room temperature but becomes quite flexible in response to heat. Strain sensors, with a diameter comparable to a human hair, were then layered onto the polymer, allowing for precise detection of the e-whiskers’ movements when hot air is passed underneath them.
With some smart calculations, this enabled the measurement of force, pressure, proximity, temperature, stiffness, and the topography of a given surface. These measurements are quite representative of the sensation of touch, and could enable differentiation between hard and soft objects, or smooth and rough surfaces.
While these sensors could easily be integrated into future robotics designs to facilitate safer, more human-like interactions, the true challenge lies in integrating these kinds of sensor technologies with human biology. Although our neurons communicate using electrical pulses, designing a two-way interface between our nervous system and a sensor requires a deep understanding of the complexity of sensory neurons. As you can imagine, while a sufficiently small electric shock to your fingertips feels like a tickle, a large enough shock can cause significant pain. One would hope that integrating this sensor technology into new prosthetic designs, along with fine-tuning of the relevant parameters for biological integration, are high up on the authors’ to-do list!
For more on this story, watch:
Read UT Dallas’ report: Team’s E-Whiskers May Be a Touchstone for Future of Electronic Skin…