Thin Film Encapsulation for LCP-Based Flexible Bioelectronic Implants: Comparison of Different Coating Materials Using Test Methodologies for Life-Time Estimation
Liquid crystal polymer (LCP) has gained wide interest in the electronics industry largely due to its flexibility, stable insulation and dielectric properties and chip integration capabilities. Recently, LCP has also been investigated as a biocompatible substrate for the fabrication of multielectrode...
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| Format: | Article |
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MDPI AG
2022-03-01
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| Series: | Micromachines |
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| Online Access: | https://www.mdpi.com/2072-666X/13/4/544 |
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| author | Anna Pak Kambiz Nanbakhsh Ole Hölck Riina Ritasalo Maria Sousa Matthias Van Gompel Barbara Pahl Joshua Wilson Christine Kallmayer Vasiliki Giagka |
| author_facet | Anna Pak Kambiz Nanbakhsh Ole Hölck Riina Ritasalo Maria Sousa Matthias Van Gompel Barbara Pahl Joshua Wilson Christine Kallmayer Vasiliki Giagka |
| author_sort | Anna Pak |
| collection | DOAJ |
| description | Liquid crystal polymer (LCP) has gained wide interest in the electronics industry largely due to its flexibility, stable insulation and dielectric properties and chip integration capabilities. Recently, LCP has also been investigated as a biocompatible substrate for the fabrication of multielectrode arrays. Realizing a fully implantable LCP-based bioelectronic device, however, still necessitates a low form factor packaging solution to protect the electronics in the body. In this work, we investigate two promising encapsulation coatings based on thin-film technology as the main packaging for LCP-based electronics. Specifically, a HfO<sub>2</sub>–based nanolaminate ceramic (TFE1) deposited via atomic layer deposition (ALD), and a hybrid Parylene C-ALD multilayer stack (TFE2), both with a silicone finish, were investigated and compared to a reference LCP coating. T-peel, water-vapour transmission rate (WVTR) and long-term electrochemical impedance spectrometry (EIS) tests were performed to evaluate adhesion, barrier properties and overall encapsulation performance of the coatings. Both TFE materials showed stable impedance characteristics while submerged in 60 °C saline, with TFE1-silicone lasting more than 16 months under a continuous 14V DC bias (experiment is ongoing). The results presented in this work show that WVTR is not the main factor in determining lifetime, but the adhesion of the coating to the substrate materials plays a key role in maintaining a stable interface and thus longer lifetimes. |
| first_indexed | 2024-03-09T04:24:07Z |
| format | Article |
| id | doaj.art-a4e6e84ede9a4be0a19bcdc51a70167c |
| institution | Directory Open Access Journal |
| issn | 2072-666X |
| language | English |
| last_indexed | 2024-03-09T04:24:07Z |
| publishDate | 2022-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Micromachines |
| spelling | doaj.art-a4e6e84ede9a4be0a19bcdc51a70167c2023-12-03T13:43:50ZengMDPI AGMicromachines2072-666X2022-03-0113454410.3390/mi13040544Thin Film Encapsulation for LCP-Based Flexible Bioelectronic Implants: Comparison of Different Coating Materials Using Test Methodologies for Life-Time EstimationAnna Pak0Kambiz Nanbakhsh1Ole Hölck2Riina Ritasalo3Maria Sousa4Matthias Van Gompel5Barbara Pahl6Joshua Wilson7Christine Kallmayer8Vasiliki Giagka9Department of Microelectronics, Delft University of Technology, 2628 CD Delft, The NetherlandsDepartment of Microelectronics, Delft University of Technology, 2628 CD Delft, The NetherlandsDepartment of System Integration and Interconnection Technologies, Fraunhofer Institute for Reliability and Micro-Intregration IZM, 13355 Berlin, GermanyPicosun Oy, Tietotie 3, 02150 Espoo, FinlandCorTec GmbH, 79108 Freiburg, GermanyComelec SA, 2301 La Chaux-de-Fonds, SwitzerlandDepartment of System Integration and Interconnection Technologies, Fraunhofer Institute for Reliability and Micro-Intregration IZM, 13355 Berlin, GermanyDepartment of System Integration and Interconnection Technologies, Fraunhofer Institute for Reliability and Micro-Intregration IZM, 13355 Berlin, GermanyDepartment of System Integration and Interconnection Technologies, Fraunhofer Institute for Reliability and Micro-Intregration IZM, 13355 Berlin, GermanyDepartment of Microelectronics, Delft University of Technology, 2628 CD Delft, The NetherlandsLiquid crystal polymer (LCP) has gained wide interest in the electronics industry largely due to its flexibility, stable insulation and dielectric properties and chip integration capabilities. Recently, LCP has also been investigated as a biocompatible substrate for the fabrication of multielectrode arrays. Realizing a fully implantable LCP-based bioelectronic device, however, still necessitates a low form factor packaging solution to protect the electronics in the body. In this work, we investigate two promising encapsulation coatings based on thin-film technology as the main packaging for LCP-based electronics. Specifically, a HfO<sub>2</sub>–based nanolaminate ceramic (TFE1) deposited via atomic layer deposition (ALD), and a hybrid Parylene C-ALD multilayer stack (TFE2), both with a silicone finish, were investigated and compared to a reference LCP coating. T-peel, water-vapour transmission rate (WVTR) and long-term electrochemical impedance spectrometry (EIS) tests were performed to evaluate adhesion, barrier properties and overall encapsulation performance of the coatings. Both TFE materials showed stable impedance characteristics while submerged in 60 °C saline, with TFE1-silicone lasting more than 16 months under a continuous 14V DC bias (experiment is ongoing). The results presented in this work show that WVTR is not the main factor in determining lifetime, but the adhesion of the coating to the substrate materials plays a key role in maintaining a stable interface and thus longer lifetimes.https://www.mdpi.com/2072-666X/13/4/544flexible bioelectronicsthin-film encapsulation (TFE)liquid crystal polymer (LCP)atomic layer deposition (ALD)Parylene-C (ParC)long-term encapsulation |
| spellingShingle | Anna Pak Kambiz Nanbakhsh Ole Hölck Riina Ritasalo Maria Sousa Matthias Van Gompel Barbara Pahl Joshua Wilson Christine Kallmayer Vasiliki Giagka Thin Film Encapsulation for LCP-Based Flexible Bioelectronic Implants: Comparison of Different Coating Materials Using Test Methodologies for Life-Time Estimation Micromachines flexible bioelectronics thin-film encapsulation (TFE) liquid crystal polymer (LCP) atomic layer deposition (ALD) Parylene-C (ParC) long-term encapsulation |
| title | Thin Film Encapsulation for LCP-Based Flexible Bioelectronic Implants: Comparison of Different Coating Materials Using Test Methodologies for Life-Time Estimation |
| title_full | Thin Film Encapsulation for LCP-Based Flexible Bioelectronic Implants: Comparison of Different Coating Materials Using Test Methodologies for Life-Time Estimation |
| title_fullStr | Thin Film Encapsulation for LCP-Based Flexible Bioelectronic Implants: Comparison of Different Coating Materials Using Test Methodologies for Life-Time Estimation |
| title_full_unstemmed | Thin Film Encapsulation for LCP-Based Flexible Bioelectronic Implants: Comparison of Different Coating Materials Using Test Methodologies for Life-Time Estimation |
| title_short | Thin Film Encapsulation for LCP-Based Flexible Bioelectronic Implants: Comparison of Different Coating Materials Using Test Methodologies for Life-Time Estimation |
| title_sort | thin film encapsulation for lcp based flexible bioelectronic implants comparison of different coating materials using test methodologies for life time estimation |
| topic | flexible bioelectronics thin-film encapsulation (TFE) liquid crystal polymer (LCP) atomic layer deposition (ALD) Parylene-C (ParC) long-term encapsulation |
| url | https://www.mdpi.com/2072-666X/13/4/544 |
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