Wearable pressure sensor works over broad range
Researchers at the University of Massachusetts Amherst say they have synthesized a new material that solves one of the most difficult problems in the quest to create wearable, unobtrusive sensitive sensors: the problem of pressure. While wearable electromechanical sensors are essential to improve health monitoring and off-site point-of-care applications, say the researchers, their practicality is restricted by narrow ranges of detection, failure to simultaneously sense static and dynamic pressures, and low durability.
To address this, the researchers have developed an all-fabric pressure sensor with high sensitivity in a broad range of pressures, from subtle heart pulses to body posture, exceeding that of previously-reported sensors is introduced.
“Imagine comfortable clothing that would monitor your body’s movements and vital signs continuously, over long periods of time,” says Trisha L. Andrew, professor of chemistry and chemical engineering. “Such clothing would give clinicians fine-grained details for remote detection of disease or physiological issues.”
One way to get this information is with tiny electromechanical sensors that turn body movements — such as the faint pulse that can be felt when a user places their hand on their chest — into electrical signals. But if the sensor wearer receives a hug or takes a nap lying on their stomach, that increased pressure overwhelms the sensor, interrupting the flow of data, and so the sensor becomes useless for monitoring natural phenomena.
To solve this problem, the researchers developed a sensor that keeps working even when hugged, sat upon, leaned on or otherwise squished by everyday interactions. The secret, say the researchers, lies in vapor-printing clothing fabrics with piezoionic materials such as PEDOT-Cl (p-doped poly(3,4-ethylenedioxythiophene-chloride).
With this method, even the smallest body movement, such as a heartbeat, leads to the redistribution of ions throughout the sensor. In other words, the fabric turns the mechanical motion of the body into an electrical signal, which can then be monitored.
Their sensor, say the researchers, is the first fabric-based sensor allowing for real-time monitoring of sensitive target populations, from workers laboring in stressful industrial settings, to kids and rehabilitation patients.
A particular advantage is that the all-fabric sensor can be worn in comfortable, loose-fitting clothing rather than embedded in tight-fitting fabrics or stuck directly onto the skin, making it far easier for the sensors to gather long-term data, such as heartbeats, respiration, joint movement, vocalization, step counts and grip strength — a crucial health indicator that can help clinicians track everything from bone density to depression.
For more, see “Humidity-Resistant, Broad-Range Pressure Sensors for Garment-Integrated Health, Motion, and Grip Strength Monitoring in Natural Environments.”