Metal-Oxide-Hydrogel Field-Effect Sensor

Hydrogels have an open cavity and porous micro-structures enabling various gases and liquids to diffuse rapidly through them and simultaneously changing their resistance, refractive index, density, color and other properties. Hence, they are ideal as programmable sensing materials. They can be, relatively easily programmed by diffusing acids, bases or ionic/non-ionic liquids or by adding nano-particles, which in addition to acting as electric or magnetic field focusing or modifying materials, add their own chemical/gas response characteristics to the hydrogel matrix element. Here we report applications of a MOSFET-like device with active channels formed by hydrogels with embedded gold nano-particles (AuNP) in gas and liquid sensing. The device consists of an open-face field effect transistor structure that can be used with different channel materials deposited directly on the device forming its active channel. The resulting metal-oxide hydrogel field-effect transistor (MOHFET) was then used to detect ethyl alcohol both in liquids and in gas phase. The sensor response was measured for ethyl alcohol gas after preconditioning the hydrogel channel in PBS (sensitivity: 2.6 μA/ml) and deionized (DI) water media (sensitivity: 7.4 μA/ml). The sensor sensitivity to ethyl alcohol in solution was 8.2×10
^-4
A/ml.