The Design, Fabrication and Characterization of Nematic Liquid Crystals Based Chemical and Biological Sensors with Electroplated Microstructures

Abstract

This paper reports the design of an electroplated microstructure comprising an interdigitated capacitance (IDC) structure for the detection of vapor-phase analytes based on nematic liquid crystal (NLC) sensors. The approach reported in this paper is the orientational transition of NLCs supported on a self-assembled monolayer (SAM) derived from copper perchlorate salt of detecting to demethyl –methylphosphonate. To improve the capacitance efficiency about the orientational transition of NLCs, this paper treats the fabrication with the pulse micro-electroplating technique. An electroplated IDC structure, 40 μm of the finger width, 10 μm of the space between fingers, and 8μm of the electroplated layer with a sharp sidewall form, was built in the device layer of a 4 inch glass wafer and filled with NLCs. And also, this structure steadily supports a thick LC film. The NLC sensor is tested by using demethyl-methylphosphonate (DMMP) detection to change the orientational response of the nematic liquid crystal molecules and demonstrated by the optical transduction as well as the capacitive transduction.

Keywords

• Nematic liquid crystals
• Chemical sensors
• Micro-fabrication
• DMMP detection