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A novel stretchable micro-electrode array (SMEA) design for directional stretching of cells

Stretchable micro-electrode arrays (SMEAs) are useful tools to study the electrophysiology of living cells seeded on the devices under mechanical stimulation. For such applications, the SMEAs are used as cell culture substrates; therefore, the surface topography and mechanical properties of the devices should be minimally affected by the embedded stretchable electrical interconnects. In this paper, a novel design and micro-fabrication technology for a pneumatically actuated SMEA are presented to achieve stretchability with minimal surface area dedicated to the electrical interconnects and a well-defined surface strain distribution combined with integrated diverse micro-patterns to enable alignment and directional stretching of cells. The special mechanical design also enables the SMEA to have a prolonged electro-mechanical fatigue life time required for long-term cyclic stretching of the cell cultures (stable resistance of electrical interconnects for more than 160 thousand cycles of 20% stretching and relaxing). The proposed fabrication method is based on the state of the art micro-fabrication techniques and materials and circumvents the processing problems associated with using unconventional methods and materials to fabricate stretchable electrode arrays. The electrochemical impedance spectroscopy characterization of the SMEA shows 4.5 MΩ impedance magnitude at 1 kHz for a TiN electrode 12 um in diameter. Cell culture experiments demonstrate the robustness of the SMEAs for long-term culturing experiments and compatibility with inverted fluorescent microscopy.