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A Chip Integrity Monitor for Evaluating Long-term Encapsulation Performance within Active Flexible Implants

: Akgun, Omer Can; Nanbakhsh, Kambiz; Giagka, Vasiliki; Serdijn, Wouter A.


Institute of Electrical and Electronics Engineers -IEEE-:
IEEE Biomedical Circuits and Systems Conference, BioCAS 2019. Conference Proceedings : October 17-19, 2019, Nara, Japan
Piscataway, NJ: IEEE, 2019
ISBN: 978-1-5090-0617-5
ISBN: 978-1-5090-0618-2
ISBN: 978-1-5386-3603-9
4 pp.
Biomedical Circuits and Systems Conference (BioCAS) <2019, Nara>
Conference Paper
Fraunhofer IZM ()

One key obstacle in employing silicon integrated circuits in flexible implants is ensuring a long-term operation of the chip within the wet corrosive environment of the body. For this reason, throughout the years, various biocompatible insulating materials have been proposed, yet, evaluating their long-term encapsulation performance on representative silicon samples still remains to be the main challenge. For this aim, in this work, a sensitive platform is introduced that can track the integrity of the chip against water and ion ingress. This platform is developed to be used for long-term monitoring of chip integrity and study of encapsulation layers in wet environments. The platform comprises a sensing array and a measurement engine and operates by tracking the changes in the inter-layer dielectric resistance within the chip. The proposed system uses a novel charge/discharge-based time-mode resistance sensor that can be implemented using simple yet highly robust circuitry. The sensor array is implemented together with the measurement engine in a standard 0.18 µm 6-metal CMOS process. For chip validation, dry and wet measurements in saline are presented in this paper.