Harvard SEAS’ Wyss Institute has developed a new textile-based sensor that registers the finer motor movements of the human body, helping create soft, wearable robots.
The highly sensitive soft capacitive sensor made of silicone and fabric moves and flexes with the human body to unobtrusively and accurately detect movement.
“We’re really excited about this sensor because, by leveraging textiles in its construction, it is inherently suitable for integration with fabric to make ‘smart’ robotic apparel,” says corresponding author and Associate Professor Conor Walsh.
The new technology consists of a thin sheet of silicone sandwiched between two layers of silver-plated, conductive fabric forming a capacitive sensor. This type of sensor registers movement by measuring the change in capacitance, or the ability to hold electrical charge, of the electrical field between the two electrodes.
The hybrid sensor’s superior performance stems from its novel manufacturing process, in which the fabric is attached to both sides of the silicone core with an additional layer of liquid silicone that is subsequently cured. This allows the silicone to fill some of the air gaps in the fabric, mechanically locking it to the silicone and increasing the surface area available for distributing strain and storing electrical charge.
The end process involves thin, flexible wires being permanently attached to the conductive fabric with thermal seam tape, allowing electrical information from the sensor to be transmitted to a circuit without a hard, bulky interface.
The team evaluated their new sensor design by performing strain experiments in which various measurements are taken as the sensor is stretched by an electromechanical tester.
According to the team, the hybrid sensor detected increases in capacitance within 30 milliseconds of strain application and physical changes of less than half a millimeter, confirming that it is capable of capturing movement on the scale of the human body.
To Test this, the researchers integrated the sensors into a glove and it was able to detect capacitance changes on individual fingers as they moved, indicating their relative positions over time.
“This work represents our growing interest in leveraging textile technology in robotic systems, and we see promising applications for motion capture ‘in the wild,’ such as athletic clothing that tracks physical performance or soft clinical devices to monitor patients in their homes. In addition, when combined with fabric-based soft actuators, these sensors will enable new robotic systems that truly mimic apparel,” says Walsh.
Image credits and excerpts: Wyss Institute/Harvard University