Stanford engineers have developed experimental stickers that record physiological signals from the skin and wirelessly send this health information to a receiver attached to clothing. It's all part of a system called BodyNet.
We tend to take the protective function of our skin for granted, and ignore their other functions to signal subtleties like a fluttering heart or a hint of embarrassment, sensors, physiological signals emanating from the skin Glue like plasters and radiate wireless readings to a receiver attached to clothing.
To demonstrate this wearable technology, the researchers pasted sensors on a subject's wrist and abdomen monitoring the person's pulse and breathing by determining how their skin dilated and contracted with each heartbeat or breath. Likewise, stickers on the elbows and knees of the person traced the movements of the arms and legs, measuring the minute tightening or relaxation of the skin with each flexion of the corresponding muscle.
Zhenan Bao, Professor of Chemical Engineering, whose laboratory described the system in August. 1
"We think one day it will be possible to create a whole body skin sensor array to capture physiological data without compromising a person's normal behavior," said Bao, who is also the KK's Lee Professor the School of Engineering.
Stretchy, comfortable, functional.
Postdoctoral researchers Simiao Niu and Naoji Matsuhisa led the 14-member team that designed the sensors for three years. Their goal was to develop a technology that is comfortable to wear and has no batteries or rigid circuitry to prevent the labels on the skin from stretching and contracting.
Their final design met these parameters with a variation of RFID Radio Frequency Identification technology to control keyless access to locked rooms. When a person holds an ID card to an RFID receiver, an antenna in the ID card removes a small amount of RFID energy from the receiver and generates a code that is then reflected back to the receiver.
The BodyNet sticker is similar to the ID: It has an antenna that intercepts part of the RFID energy coming from a receiver to the clothing to power the sensors. Subsequently, the skin data are read and returned to the nearby recipient.
For the wireless sticker to work, the researchers had to create an antenna that could stretch and bend like skin. They did this by printing metallic ink on a rubber sticker. However, if the antenna bent or stretched, the motion would make the signal too weak and unstable to be useful.
To circumvent this problem, the Stanford researchers developed a new type of RFID system that could radiate strong and accurate signals to the antenna receiver despite constant fluctuations. The battery-powered receiver then uses Bluetooth to periodically upload data from the stickers to a smartphone, computer, or other permanent storage system.
The original version of the stickers was based on tiny motion sensors for breathing and pulse measurements. The researchers are now investigating how they can integrate welding, temperature and other sensors into their antenna systems.
In order to transform their technology beyond clinical applications and into consumer-friendly devices, researchers must tackle another challenge – keeping the sensor and the receiver in proximity to one another. In their experiments, the researchers attached a receiver to the clothing directly above each sensor. One-to-one pairings of sensors and receivers would be fine for medical monitoring, but to create a BodyNet that someone could wear during training, antennas would have to be woven into clothing to receive and transmit signals, independently of where a person puts a sensor.