Ionic polymer pressure sensor with gradient shape based on ion migration.

Inspired by the sensing mechanism of an ionic polymer-metal composite (IPMC) strip, in which an electrical response is induced by an elastic stress gradient across the strip's thickness, we propose a new ionic polymer pressure sensor with a gradient shape that is based on ion migration. Under an applied pressure, an elastic stress gradient is generated across the top and bottom surfaces of the gradient, which then causes cations to migrate toward the lower pressure side. This cation redistribution then generates an electrical response. To verify this concept, a millimeter-scale ionic pressure sensor based on Nafion was fabricated by a casting method. The voltage responses of this sensor were measured using a self-made test setup. The maximum response approached tens of millivolts, which was much greater than that of an IPMC bending sensor. The sensing voltage was also investigated with respect to the various area ratios between the top and bottom surfaces and the various sensor heights. The sensitivity initially increases with increasing area ratio and then tends to reach a saturation state, whereas it rarely changed with variations in the height. Finally, the mechanical analysis showed that the size effects on the sensitivity could be explained qualitatively by the stress difference that occurs between the top and bottom surfaces. [ABSTRACT FROM AUTHOR]