Sidewall Electrodes in Microchannels for Dielectrophoretic Cell Separation and Electrochemical Detection
Meeting ID: 936 4723 0005
Chair: Prof. Mona Zebarjadi (ECE)
Advisor: Prof. Nathan Swami (ECE)
Prof. James Landers (Chem. & Mech.)
Microfluidics in biological and medical research has gained much attention in the past decade for the purposes of separation and analysis of components within a complex sample. However, electrically functional microfluidic devices for biological sensing and cell manipulation require the ability to modulate electric field profiles over the channel width and depth, which is especially challenging to fabricate with minimum lithography steps. Metal deposition is the most ubiquitous method for integrating electrodes in microchannels, but the traditional deposition method is limited to planar electrodes, which have low electric field extents along the depth of the channel, thereby making them unsuitable for applications wherein sensing and manipulation are required over the channel depth. To address the channel depth requirement without highly specialized sidewall metal deposition, alternative electrode fabrication methods have been explored, such as conductive liquid electrodes, Ag-PDMS electrodes, and liquid metal electrodes. Liquid electrodes Ag-PDMS electrodes has been a popular choice; however, conductive fluid is not stable over time as it can crystalize, therefore, changing its conductivity and Ag-PDMS presents low electrical conductivity which reduces field coupling. Here, we present a facile fabrication method and its design parameters for integrating liquid metal to form solid metal 3D sidewall electrodes to enable dielectrophoretic cell separation and electrochemical detection in a microchannel over its entire depth. A low melting point alloy consisting of 51% indium, 32.5% bismuth, and 16.5% tin (Field’s metal) was used to pattern the microchannels at 65 C and solidifying at room temperature. Specifically, an electrode and sample channel are co-fabricated in a single lithography step and sequentially filled to enable electrically functional microfluidic separation and detection. Three distinct confinement approaches are examined for creating electrode channels that are physically separated from biological sample channels, but electrically coupled for enabling dielectrophoretic separation and electrochemical detection.