Tracking health with paper electronics

Muhammad M. Hussain and his team at King Abdullah University of Science & Technology are on a path paved with sticky notes and silicon to make wearable health trackers more affordable for everyone. Using sticky notes, silver ink, aluminum foil, and clean-room wipes, Hussain’s team created low-cost pressure, moisture, and temperature sensors connected to flexible silicon circuits for data handling and transmission. The team’s work has been accepted and will be published soon in Adv. Mater. Technol. By printing silver ink coils and capacitors on cellulose sticky note substrates, the team created simple temperature and moisture sensors, respectively. Changing temperatures are detected as changes in the ink’s electrical resistance, whereas the paper’s dielectric permittivity responds to moisture introduced by sweat, measurably altering the sensor’s electronic profile. To track a person’s pulse, the team built pressure sensors with clean-room wipes sandwiched between strips of aluminum foil. A wipe’s microfibers compress and relax along with the staccato blood flow through the wrist’s radial artery, causing the sandwich sensor’s capacitance to fluctuate with the heartbeat. Each sensor is mounted to a 3-D-printed wristband, resulting in a device that costs about $25 to make, the team reports.