Redox-Magnetohydrodynamically Controlled Fluid Flow with Poly(3,4-ethylenedioxythiophene) Coupled to an Epitaxial Light Sheet Confocal Microscope for Image Cytometry Applications

Abstract

We present the merging of two technologies to perform continuous high-resolution fluorescence imaging of cellular suspensions in a deep microfluidics chamber with no moving parts. An epitaxial light sheet confocal microscope (e-LSCM) was used to image suspensions enabled by fluid transport via redox-magnetohydrodynamics (R-MHD). The e-LSCM features a linear solid state sensor, oriented perpendicular to the direction of flow, that can bin the emission across different numbers of pixels, yielding electronically adjustable optical sectioning. This, in addition to intensity thresholding, defines the axial resolution, which was validated with an optical phantom of polystyrene microspheres suspended in agarose. The linear fluid speed within the microfluidics chamber was uniform (0.16-2.9%) across the 0.5-1.0 mm lateral field of view (dependent upon the chosen magnification) with continuous acquisition. Also, the camera's linear exposure periods were controlled to ensure an accurate image aspect ratio across this span. Poly(3,4-ethylenedioxythiophene) (PEDOT) was electrodeposited as an immobilized redox film on electrodes of a chip for R-MHD, and the fluid flow was calibrated to specific linear speeds as a function of applied current. Images of leukocytes stained with acridine orange, a fluorescent, amphipathic vital dye that intercalates DNA, were acquired in the R-MHD microfluidics chamber with the e-LSCM to demonstrate imaging of biological samples. The combination of these technologies provides a miniaturizable platform for large sample volumes and high-throughput, image-based analysis without the requirement of moving parts, enabling development of robust, point-of-care image cytometry.