Microfluidic platform for cell analysis using through-polydimethylsiloxane micro-tip electrode array

Abstract In this study, we present the fabrication and measurement of a microfluidic system combined with a through-polydimethylsiloxane (PDMS) microtip electrode that can be used to measure the photosynthetic reaction of green algae cells in the microfluidic channel. The conventional single-cell based method has a disadvantage of low efficiency. To solve this problem, we propose a method of electrical feed-through interconnection of a microfluidic channel platform using a microtip electrode array. Silicon microtip arrays were fabricated using a combination of processes using deep reactive ion etching (DRIE) and reactive ion etching (RIE) steps. In the RIE process, the shape of the cylindrical silicon pillar changed from a cylinder to a probe shape according to the local change of the side-wall etching rate of the silicon pillar. The local ultra-micro electrode (UME) structure was fabricated using a self-alignment fabrication method without additional photolithography steps, and its electrochemical properties were confirmed using a cyclic voltammetry (CV) experiment. The photosynthetic algae cells were stacked in the PDMS microfluidic chip and then combined with the microtip electrode array using an acrylic jig. After assembling the microtip electrode array, the microtip was confirmed to penetrate the PDMS thin film through the CV experiment. When irradiated with light, the current induced by the oxygen produced by a photosynthetic reaction in the algae cells (stacked in the PDMS microfluidic chip) was measured using the microtip electrode array. Further, experiments were conducted to measure the force applied by the acrylic jig when combining the microtip electrode array with the PDMS microfluidic chip.