gms | German Medical Science

Objective: The aim is to design a novel chip integrating microfluidics, organic electronic ion pumps and a microelectrode array (MEA) for localized electroporation, stimulation and recording. With this multifunctional MEA, three interfaces are established to study the pathological retina and to evaluate different treatment approaches in in-vitro experiments.

Materials and Methods: The microfluidic structures are fabricated within a fused silica wafer through selective laser-induced etching. Onto this pre-processed wafer, the cleanroom fabrication process takes place. First, a 5 μm thick dry photoresist is applied to seal the microfluidic outlet holes on the wafer surface. Then bottom electrodes are fabricated by application and patterning of photoresist, followed by evaporation of titanium/gold/titanium layers and a subsequent lift-off step. On top of these electrodes, a cation exchange membrane is created out of PEDOT:PSS which is patterned by application of highly fluorinated resist and reactive ion etching (RIE). Electrical overoxidation ensured loss of electrical conductivity. Isolation of the electrodes is done by chemical vapor deposition of a 3.5 μm thick layer of Parylene-C (Pa-C). Additional gold electrodes are evaporated on top of the employing a titanium adhesion layer. 2 μm thick electrodes are electroplated after the application of photoresist. Another photoresist plus chemical wet etching shaped the electrodes. A final Pa-C layer is applied to isolate the upper electrodes. After application of a photoresist, RIE is used to open the microfluidic and the ionic channels as well as the electrodes.

Results: The manufacturing process was successfully implemented without delamination issues. Processing parameters were chosen appropriately.

Discussion: This work demonstrated the feasibility of a triple-interface chip for in-vitro experiments. Future work will focus on integrating the microfluidic structure into a flexible polymer to enable in-vivo studies.

Funding: This work is supported by the Deutsche Forschungsgemeinschaft (DFG), grant number 424556709/GRK2610.