Hydrogel Gold Nanoparticle Switch

Design and operation of a metal-oxide hydrogel field-effect transistor (MOHFET) with channel composed of a hydrogel embedded with gold nanoparticles (AuNP) is discussed. Hydrogels have low ionic and electronic conductivities that change as a function of their ionic contents. AuNP incorporated in the hydrogel increases its conductivity by >2x and also introduces large conduction nonlinearity (field focusing by AuNP and smaller soft breakdown field) as a function of channel electric fields. The hydrogel provides a convenient medium with distributed springs connecting AuNPs to the MOHFET drain and source. The measured electrical conductivity in our pure hydrogel was 611 S/m and it increased to 1540 S/m in AuNP hydrogel. The hydrogel Young's modulus was 14 +/- 2 kPa that increased to 21 +/- 2 kPa with Au-NP incorporation. The I-ON/I-OFF ratio of MOHFET was similar to 10(4) and its subthreshold swing was 148.72 mV/dec at V-ds = 2 V. Hydrogels' porous structure and very flexible electrical and mechanical characteristics make them excellent candidate as binding media to incorporate suitable nanoparticles in sensors and electronic devices.