Not all high-tech equipment has to put a dent in your wallet. In fact, with enough ingenuity, complex electronics can be manufactured with items commonly found around the house.
What do you think you could make out of sticky notes, aluminum foil, sponges, and tape? The most I could come up with is an art project that probably wouldn’t even be worthy to be hung on the refrigerator. But in the hands of a team of electrical engineers from the King Abdullah University of Science and Technology (KAUST), these items—usually reserved for a drawer in the kitchen—became a flexible, multifaceted, “artificial skin” sensor.
Dubbed “Paper Skin,” the MacGyvered sensor measures touch, pressure, acidity, and humidity. The paper-based technology connects to a device that detects electrical conductivity changes, based on outside stimuli.
Temperature sensing is achieved with either the aluminum foil or a conductive silver pen. The sensor’s resistance varies based on temperature’s effect on vibrations in the metal or ink’s lattice structure.
Thanks to cellulose fiber’s porous properties, Paper Skin receives an accompanying boost of capacitance whenever humidity increases. Coloring the sticky note with an HB pencil provides a sensing film for pH. When exposed to a solution, the paper becomes saturated (thanks again to porous properties) and resistance increases due to an acid, and decreases when in contact with a base. The redox reaction between graphite and hydroxyl ions ultimately measures the acidity.
As the pressure applied to Paper Skin increases, the sensor’s output capacitance decreases due to the sponge’s contortion, measuring force exerted. Tactile sensing is achieved because a finger will interfere with the electric field surrounding the capacitor. (This is what will make heartbeat detection possible!) An air-gap-based design permits sensor response to lower pressure. The entire pressure-sensing platform is able to detect force, touch, motion, direction, and proximity testing. (More information on the study can be found here.)
“The next stage will be to optimize the sensor’s integration on this platform for applications in medical monitoring systems,” said KAUST Integrated Nanotechnology Lab’s Muhammad Mustafa Hussain in a KAUST article. The flexible and conformal sensory platform will enable simultaneous real-time monitoring of body vital signs, such as heart rate, blood pressure, breathing patterns, and movement.”
There are still issues with Paper Skin before it can be considered for a commercial autonomous, flexible, multifunctional sensor. The paper skin itself needs more development for wireless communication. Plus, since the sensor is made of common household items that aren’t typically very sturdy, tests are needed to analyze the sensor’s shelf life, and how it performs when subjected to bending.
For now, time to explore what other medtech components are lurking in my kitchen drawer!