Print Email Facebook Twitter Silicone encapsulation of thin-film SiOx , SiOx Ny and SiC for modern electronic medical implants Title Silicone encapsulation of thin-film SiOx , SiOx Ny and SiC for modern electronic medical implants: A comparative long-term ageing study Author Lamont, C. (University College London (UCL)) Grego, T. (University College London (UCL)) Nanbakhsh, K. (TU Delft Bio-Electronics) Idil, A. Shah (University College London (UCL)) Giagka, Vasiliki (TU Delft Bio-Electronics; Fraunhofer Institute for Reliability and Microintegration IZM) Vanhoestenberghe, A. (University College London (UCL)) Cogan, S. (University of Texas at Dallas) Donaldson, N. (University College London (UCL)) Date 2021 Abstract Objective. Ensuring the longevity of implantable devices is critical for their clinical usefulness. This is commonly achieved by hermetically sealing the sensitive electronics in a water impermeable housing, however, this method limits miniaturisation. Alternatively, silicone encapsulation has demonstrated long-term protection of implanted thick-film electronic devices. However, much of the current conformal packaging research is focused on more rigid coatings, such as parylene, liquid crystal polymers and novel inorganic layers. Here, we consider the potential of silicone to protect implants using thin-film technology with features 33 times smaller than thick-film counterparts. Approach. Aluminium interdigitated comb structures under plasma-enhanced chemical vapour deposited passivation (SiO x , SiO x N y , SiO x N y + SiC) were encapsulated in medical grade silicones, with a total of six passivation/silicone combinations. Samples were aged in phosphate-buffered saline at 67 °C for up to 694 days under a continuous 5 V biphasic waveform. Periodic electrochemical impedance spectroscopy measurements monitored for leakage currents and degradation of the metal traces. Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, focused-ion-beam and scanning-electron- microscopy were employed to determine any encapsulation material changes. Main results. No silicone delamination, passivation dissolution, or metal corrosion was observed during ageing. Impedances greater than 100 GΩ were maintained between the aluminium tracks for silicone encapsulation over SiO x N y and SiC passivations. For these samples the only observed failure mode was open-circuit wire bonds. In contrast, progressive hydration of the SiO x caused its resistance to decrease by an order of magnitude. Significance. These results demonstrate silicone encapsulation offers excellent protection to thin-film conducting tracks when combined with appropriate inorganic thin films. This conclusion corresponds to previous reliability studies of silicone encapsulation in aqueous environments, but with a larger sample size. Therefore, we believe silicone encapsulation to be a realistic means of providing long-term protection for the circuits of implanted electronic medical devices. Subject accelerated testselectrochemical impedance spectroscopyencapsulationimpedance spectroscopyintegrated circuitlife-testingsilicone To reference this document use: http://resolver.tudelft.nl/uuid:1631ecc9-c9ac-438d-9198-95069187e09d DOI https://doi.org/10.1088/1741-2552/abf0d6 ISSN 1741-2560 Source Journal of Neural Engineering, 18 (5), 1-16 Part of collection Institutional Repository Document type journal article Rights © 2021 C. Lamont, T. Grego, K. Nanbakhsh, A. Shah Idil, Vasiliki Giagka, A. Vanhoestenberghe, S. Cogan, N. Donaldson Files PDF Lamont_2021_J._Neural_Eng ... 055003.pdf 2.07 MB Close viewer /islandora/object/uuid:1631ecc9-c9ac-438d-9198-95069187e09d/datastream/OBJ/view