Simultaneous sum frequency generation (SFG) vibrational spectra and electrical measurements were obtained on organic field effect transistors (OFETs) fabricated with the semiconductors: 5,5′-bis(4-hexylphenyl)-2,2′-bithiophene (6pttp6), 5,5′-bis(4-ethylphenyl)-2,2′-bithiophene (2pttp2), and pentacene. In-situ measurements during gating of the OFETs showed strong correlations between vibrational spectra and electronic properties. One correlation involved structural changes in the hexyl and ethyl groups, of 6pttp6 and 2pttp2, respectively, and saturation source-drain current; the correlation was observed only at negative gate voltages (when carrier injection was possible) and was more pronounced for 6pttp6, with the introduction of gauche defects in the longer hexyl chains. A second correlation between the dependence of SF nonresonant background on gate voltage and electronic mobility was observed on OFETs of all three semiconductors, at both positive and negative gate voltages. This correlation suggests that a common molecular structural packing element may determine the magnitude of both the electronic mobility and higher order nonlinear optical susceptibilities in oligomeric thin films. These results also demonstrate the utility of SFG in probing molecular structural and electrical field effects at the buried semiconductor-dielectric interface of OFETs.

We describe a microfluidic scheme based on remotely controlled self-assembled containers that allows spatio-temporal control over nanoliter-scale chemical reactions. We discuss finiteelement simulations of the inductive coupling of radio-frequency radiation to the containers; this coupling enables remotely triggered release of chemical reactants. We demonstrate on-demand chemical release from stationary and mobile containers patterned with different porosities. We also explore reactions between chemicals released from two containers that form liquid products and deposit solid precipitates. We argue that these remotely controlled metallic containers provide an attractive platform for carrying out reconfigurable microfluidics "without channels."