Kids' Play Putty Forms "Squishy Circuits" Usable as Ultra-Cheap, Self-Healing Bio-Sensor Electrodes
Costing just $0.01 per electrode, this child's toy can equal — or better — the performance of commercial gel electrodes.
Researchers at the University of Massachusetts Amherst's department of biomedical engineering have come up with an unusual use for play-putty, store-bought or homemade: building "squishy bioelectronic circuits" that can be used as electrodes for electroencephalography (EEG), electrocardiography (ECG), electromyography (EMG), and electrooculography (EOG) — measuring activity in the brain, heart, muscles, and eyes respectively.
"[Squishy circuits] are literally child's play putty, that is also conductive," senior author Dmitry Kireev, assistant professor of biomedical engineering at the University of Massachusetts, explains of the team's work. "We used the squishy circuits as an interface to measure electricity or measure bioelectrical potentials from a human body."
Play-putty or play-dough is a simple, soft material beloved by kids worldwide — and it's easy to make, requiring only flour, water, salt, cream of tartar, and a little oil, plus optional food coloring for aesthetics. The salt acts as a preservative to prevent the dough from spoiling, but it does something else too: turns the dough conductive, allowing it to carry an electrical signal.
This is well-known, and salt-enriched dough has been used in the past to build simple soft circuits and capacitive touch-sensors as a means of getting younger kids involved with electronics — but Kireev and colleagues have found the same material could have a broader application, standing in for commercial electrodes in EEG, EMG, EOG, and ECG sensing applications — being soft and gentle, bio-compatible, and extremely cheap.
The latter is a particular selling point to the squishy-circuit approach: where commercial electrodes cost between $0.25 and $1 each, the dough versions cost around $0.01 — even when using commercial dough. The material can be molded to match the contours of the skin, is self-healing, the electrodes can easily be repositioned and reused — and, in testing, performed on-par with one commercial gel electrode and twice as good as another.
The team's work has been published in the journal Device under open-access terms.