Low-cost microfluidic impedance device with multi-layer field's metal electrodes

Abstract

Three-dimensional (3D) spheroids and organoids are complex multi-cellular structures widely used in biomedical research. Major bottlenecks in imaging these large structures (~200μm to few mm in size) are the poor light penetration depth, focusing issues, and the requirement for multi-colour antibodies staining. Impedance spectroscopy is the electrical-based measurement of biological specimens at different frequencies, which is label-free and enables multiple measurements of the same sample in long-term studies. With an increasing level of living standards worldwide, another emerging application of impedance spectrometry is the testing of food safety and quality as it requires real-time assay readout and can be readily deployed in resource-poor or non-lab settings. In this thesis, we first report a novel electrode array fabrication method for microfluidic impedance tomography that is capable of performing impedance spectrometry of large objects. Two fabrication methods using soft lithography and 3D printing were evaluated in terms of the ease of fabrication replicability as well as quality of impedance tomography images. Using PalmSens4 as the impedance analyser, our results showed that microfluidic impedance tomography using 3D printed electrodes can successfully profile 3D structures of different shapes, composite objects with different material layers, and identify cancer spheroids and different types of meat (fish meat and fish skin) based on differential impedance signatures. These results strongly suggest the feasibility for further technology development and optimisation to obtain tomographic images of greater resolution.