Voltage controlled Resistive and Capacitive Response of Nematic Liquid Crystal (LC) and LC Composites for DC and RF Switching Applications

M. Munna, T. Nandy, R.A. Coutu_Jr.
Marquette University,
United States

Keywords: liquid crystal, DC and DF switch, LC composite

Summary:

Liquid Crystal (LC) are widely used in display devices, electro-optic modulators, and optical switches. In these types of devices an electric field is applied which modulates the optical properties of the LC material. There are only a few works done on all electrical switches and sensors. In this research, our goal is to design, simulate and fabricate LC switching devices and test the capacitive and resistive responses under DC and low frequency AC loads using various electrode configurations. We will study electrode configurations that result in high sensitivity, low response time, and high on/off ratio. Resistivity and capacitance/dielectric constant changes in LCs tend to be very small with applied DC and low frequency Electric fields [1]. This makes traditional LC a less preferable choice for DC and RF switching applications. When nanoparticles (i.e. Au, CNT, TiO2, etc.) [2-4] are mixed, however with traditional LC materials, the resulting composite LC properties become more attractive for resistive and capacitive switching applications. The conductivity of composite LC material can change 2 to 3 orders of magnitude, compared to only 2-3 times change when using unaltered liquid crystals [2-4]. Similarly, the change in capacitance also increases when the applied electric field increases. We will investigate composite liquid crystal, as well as pure liquid crystal as a switching material for DC and RF switching. We will use micromachining processes to fabricate our novel switching devices. During DC testing, response time, settling time, on/off ratio for the DC switching will be investigated. During RF testing, the insertion loss, isolation etc. will be compared for RF switching applications. In both RF and DC applications, we expect that LC composites will have improved performance over pure LC materials.