Development of a process for the manufacturing of SU-8 100 for the use in cell culture

Blume, Grit; Mielke, Gabriela; Kohnert, Jessica; Pörtner, Ralf; Trieu, Khiem H

doi:10.1177/0883911518765216

Cited by 2 publications

(1 citation statement)

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“…Currently, the most used materials for this purpose are the polymers parylene C, polyimide and SU-8 [4]. However, the negative photoresist SU-8 needs to be processed adequately to avoid cytotoxicity resulting from leachables [5]. Comparing the mechanical stability of parylene C and polyimide, the polymer polyimide has a superior stability, particularly for the application as a flexible substrate for neural implants [6].…”

Section: Introductionmentioning

confidence: 99%

Towards Long-Term Stable Polyimide-Based Flexible Electrical Insulation for Chronically Implanted Neural Electrodes

et al. 2021

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For chronic applications of flexible neural implants, e.g., intracortical probes, the flexible substrate material has to encapsulate the electrical conductors with a long-term stability against the saline environment of the neural tissue. The biocompatible polymer polyimide is often used for this purpose. Due to its chemical inertness, the adhesion between two polyimide layers is, however, a challenge, which can lead to delamination and, finally, to short circuits. The state-of-the-art method to improve the adhesion strength is activating the polyimide surface using oxygen reactive ion etching (O2 RIE). However, the influence of the process variations (etching time, bias power) on the long-term stability is still unclear. Therefore, we establish a test method, where the aging of a gold interdigital structure embedded in two polyimide layers and immersed in saline solution is accelerated using an elevated temperature, mechanical stress and an electrical field. A continuous measurement of a leakage current is used to define the failure state. The results show that the variation of the O2 RIE plasma process has a significant effect on the long-term stability of the test samples. Comparing the two different plasma treatments 0.5 min at 25 W and 1 min at 50 W, the long-term stability could be increased from 20.9 ± 19.1 days to 44.9 ± 18.9 days. This corresponds to more than a doubled lifetime. An ideal solution for the delamination problem is still not available; however, the study shows that the fine-tuning of the fabrication processes can improve the long-term stability of chronically implanted neural electrodes.

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Section: Introductionmentioning

confidence: 99%