- Innovative nanoelectromechanical switches (NEMS) have the prospects to reduce device actuation voltages as compared to traditional semiconductor devices. Current research on NEMS seeks to avoid irreversible adhesion at the nanoscopic level, which results in device failure. Minimizing leakage currents and increasing device longevity are additional goals of this approach. The switches derive their switching by modulating a tunneling current through a nanometer-scale gap of an organic thin film between two electrodes. Compressing the film decreases the tunneling gap and creates an increase the current; conversely, the restoring force of the compressed (strained) organic layer turns off the switch. This squeezable switch has been termed a “squitch”.1 The properties of the squitch are highly dependent on the organic material sandwiched between the electrodes. Modified poly(3-hexylthiophene-2,5-diyl) (P3HT) is being explored for the design of this organic layer due to its conductive properties and compatibility with gold electrode surfaces. Recent and ongoing work in the Swager group has resulted in a simple, two-step, post-polymerization procedure for the modification of P3HT. This procedure involves bromination of P3HT with N-bromosuccinimide followed by lithium-halogen exchange and quenching of the anion with electrophiles. This method was used to create
ketone-modified P3HT and also allows for a variety of functional groups to be installed by varying the electrophile. Several functional groups including long, branched, and unsaturated alkyl chains or poly(ethylene) glycol groups were examined in order to adjust the electronic and packing properties of P3HT, to achieve the desired mechanical properties for compression, and to reduce the actuation (switching) voltage below one volt.