Arindam Phani

Photothermal Electrical Resonance Spectroscopy of Physisorbed Molecules on a Nanowire Resonator.

Mid-infrared (IR) photothermal spectroscopy of adsorbed molecules is an ideal technique for molecular recognition in miniature sensors with very small thermal mass. Here, we report on combining the photothermal spectroscopy with electrical resonance of a semiconductor nanowire for enhanced sensitivity, selectivity, and simplified readout. Wide band gap semiconductor bismuth ferrite nanowire, by virtue of its very low thermal mass and abundance of surface states in the band gap, facilitates thermally induced charge carrier trapping in the surface states, which affects its electrical resonance response. Electrical resonance response of the nanowire varies significantly depending on the photothermal spectrum of the adsorbed molecules. We demonstrate highly selective detection of mid-IR photothermal spectral signatures of femtogram level molecules physisorbed on a nanowire by monitoring internal dissipation response at its electrical resonance.

Wireless single contact power delivery

We expand on our recently developed single contact transmission method and apply it toward short-range wireless power delivery. The connection between a conductive surface and a receiver, which was directly connected in our initial system, can be made capacitive by extending the receiver a short distance off the surface. This allows the system to function in a purely wireless mode. We demonstrate the wireless transmission of power to a 25 W load at varying distances from an aluminum foil sheet. The transfer efficiency is given with respect to receding distance from the sheet with an average efficiency of 80% over a 3 cm separation for the experimental system.

A nanostructured surface increases friction exponentially at the solid-gas interface.

According to Stokes’ law, a moving solid surface experiences viscous drag that is linearly related to its velocity and the viscosity of the medium. The viscous interactions result in dissipation that is known to scale as the square root of the kinematic viscosity times the density of the gas. We observed that when an oscillating surface is modified with nanostructures, the experimentally measured dissipation shows an exponential dependence on kinematic viscosity. The surface nanostructures alter solid-gas interplay greatly, amplifying the dissipation response exponentially for even minute variations in viscosity. Nanostructured resonator thus allows discrimination of otherwise narrow range of gaseous viscosity making dissipation an ideal parameter for analysis of a gaseous media. We attribute the observed exponential enhancement to the stochastic nature of interactions of many coupled nanostructures with the gas media.