Liquid Crystal Sensors with Capacitive Transduction

Abstract

In this paper, the theory for tracking the average molecular orientation of a liquid crystal material via capacitive sensing of anisotropic media is presented. Tracking the director axis of a nematic liquid crystal material can be achieved by two capacitance measurements. The sensitivity for the sensor at different alignments is studied. Both the experimental and calculated values for fringing capacitances of a selected interdigitated fingers sensor are presented.

Neuro-fuzzy system to monitor uniaxial nematic liquid crystal profile

“…A change in the structure at the surface caused by the binding of a chemical or biological agent is amplified into a significant change in the average molecular alignment of the LC film. The collective behavior of LC molecules coupled with their large dielectric anisotropy yield measurable capacitive changes for a director change on the order of a fraction of a degree [4], [5]. In general, LC is handled as anisotropic and inhomogeneous over the area of interest.…”

“…In previous works [4], [5], the authors presented capacitive transduction techniques for ordered and partially disordered LC systems that offer significant advantages over the present optical techniques. In the previous works, capacitance modeling of the interdigitated structure sensors associated with the LC materials was presented.…”

“…In the previous works, capacitance modeling of the interdigitated structure sensors associated with the LC materials was presented. It is been shown that two capacitance measurements can uniquely track the director axis orientation in ordered LC film as in [4], where in [5], it is proven that additional capacitance measurement can lead to the order parameter in partially disorder LC film. In [5], three orthogonal capacitances are modeled and calculated as function of the director axis orientation and the order parameter.…”

Capacitive Based Liquid Crystal Chemical and Biological Sensors

“…The authors theoretically proved and experimentally verified that two capacitive measurements can uniquely track changes of the molecular orientation in an ordered LC film. Although the effort in [4] has been demonstrated in fully ordered systems, LC films in practical sensors are partially disordered. The innovation of this paper is to extend the capacitive transduction method to simulate inhomogeneous, partially disordered and highly anisotropic LC films.…”

“…In a previous work [4], the authors presented a capacitive transduction technique for ordered LC systems that offered significant advantages over the optical techniques. For example, the ability to identify and track the deformation rather than simply sensing an LC distortion.…”