I-V and Gain Characteristics of Electrowetting-Based Liquid Field Effect Transistor

Abstract

There is great interest in µfluidic devices due to important applications ranging from biotechnology [1] to flat panel displays [2]. An important enabling technology in µfluidics is based on the electrowetting (EW) effect [3], which controls the contact angle of a liquid on a hydrophobic surface through the application of an electric field. Many operations can be performed through external control [4] (such as droplet dispensing, transport, splitting, and mixing), leading to increasingly sophisticated applications for lab-on-chip [5] devices. One of the limitations of µfluidic devices is that the information contained in the fluid has to be converted in an electronic form in order to interact with our pervasive digital world. This conversion typically is performed through either direct optical sensing or combined with optical excitation of fluorescent dyes, which is cumbersome, limited in information processing, and expensive. We have invented [6] an EW-based liquid state field effect transistor (LiquiFET), which is very similar in concept to conventional semiconductor FETs but operates in the liquid state and thus can directly convert charge-related information from the liquid state into conventional electronic signals. Fig. 1 illustrates the LiquiFET structure and current control achieved by EW between competitive conducting/insulating fluids. Fig. 1 Schematics of LiquiFET structure: (a) cross section in off state, (b) cross section in on state, (c) top view in off state, and (d) top view in on state.

A brief history of liquid computers

“…The breadth and depth of the liquid electronics 'eco-system' would require a separate review paper. Example 'species' of liquid electronics devices are liquid-solid phase reversible change of conductivity controlled by temperature [182], fieldcontrolled electrical switch [183], liquid field effect transistor [184] and optical liquid droplet switch [185]. There is a also a huge, and largely unexplored, potential in combining mechanical properties of the liquid jets, droplets and marbles with electrical and optical properties of their solvents and solutes.…”