Access Type

Open Access Dissertation

Date of Award

January 2017

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Electrical and Computer Engineering

First Advisor

Mark M. Cheng

Abstract

Variable focal length liquid microlenses are the next candidate for a wide variety of applications. Driving mechanism of the liquid lenses can be categorized into mechanical and electrical actuation. Among different actuation mechanisms, EWOD is the most common tool for actuation of the liquid lenses. In this dissertation, we have demonstrated versatile and low-cost miniature liquid lenses with graphene as electrodes. Tunable focal length is achieved by changing both curvature of the droplet using electrowetting on dielectric (EWOD) and applied pressure. Ionic liquid and KCl solution are utilized as lens liquid on the top of a flexible Teflon-coated PDMS/parylene membrane. Transparent and flexible, graphene allows transmission of visible light as well as large deformation of the polymer membrane to achieve requirements for different lens designs and to increase the field of view without damaging of electrodes. Another advantage of graphene compared to non-transparent electrodes is the larger lens aperture. The tunable range for the focal length is between 3 and 7 mm for a droplet with a volume of 3 μL. The visualization of bone marrow dendritic cells is demonstrated by the liquid lens system with a high resolution (more than 456 lp/mm). The Spherical aberration analysis is performed using COMSOL software to investigate the optical properties of the lens under applied voltages and pressure. We propose a prototype of compound eye with specific design of the electrodes using both tunable lenses and tunable supporting membrane. The design has many advantages including large field of view, compact size and fast response time. This work maybe applicable in the development of the next generation of cameras, endoscopes, cell phones on flexible platform. We also proposed here the design and concept of self-powered wireless sensor based on the graphene radio-frequency (RF) components, which are transparent, flexible, and monolithically integrated on biocompatible soft substrate. We show that a quad-ring circuit based on graphene transistors may simultaneously offer sensing and frequency modulation functions. This battery-free and transparent sensors based on newly discovered 2D nanomaterials may benefit versatile wireless sensing and internet-of-things applications, such as smart contact lenses/glasses and microscope slides.

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