Sensing devices based on Graphene Field Effect Transistors (G-FET) have been demonstrated by several groups to show excellent sensitivity for a variety of chemical agents. These devices are based on measuring changes in the electrical conductivity of graphene when exposed to various chemicals. However, because of its unique band structure, graphene also exhibits changes in its optical response upon chemical exposure. The conical intersection of the valence and conduction bands results in a low density of states near the Dirac point. At this point, chemical doping resulting from molecular binding to graphene can result in dramatic changes in graphene’s optical absorption. Here we will discuss our recent work in developing a graphene planar lightwave circuit (PLC) sensor which exploits these optical and electronic properties of graphene to demonstrate chemical sensitivity. The devices are based on a strong evanescent coupling of graphene via electrically gated silicon nanowire waveguides. A strong response in the form of a reversible optical attenuation change of 6 dB is shown when these devices interact with toxic industrial chemicals such as iodine and ammonia. The optical transition can also be tuned to the optical c-band (1530-1565 nm) which enables these devices to operate at telecom wavelengths.
Dielectric electroactive polymers respond to an applied electric field by deformation as described by the Maxwell effect.
The response depends on the polymers' dielectric constant and stiffness. Addition of a high dielectric filler material has
been shown to enhance the strain response. We report preliminary results on the enhancement of p(EGPEA) polymer
films by addition of 1 w/v% of gold-capped, 500 nm SiO2 Janus particles (JP-SiO2). In comparison to pure p(EGPEA)
and p(EGPEA) filled with unmodified SiO2 particles, JP-SiO2 p(EGPEA) films show an up to 24 times enhanced
response. Measurement of the relative dielectric constant and the Young's Modulus indicate that the Janus particle
additive increases the relative dielectric constant of the films, while at the same time decreasing the Young's Modulus
leading to an overall larger electrostrictive coefficient for the JP-SiO2 p(EGPEA) films.