Corrosion Behavior of Parylene-Metal-Parylene Thin Films in Saline

Li, Wen; Rodger, Damien C.; Menon, Parvathy; Tai, Yu‐Chong

doi:10.1149/1.2897437

Cited by 42 publications

(23 citation statements)

References 2 publications

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“…Failure modes of neural probes manifested as a loss of neural recording capability can be classified into those relating to device design [29, 35] (above the arrow) and foreign-body response [34, 36] (below the arrow). Design failure mechanisms include mechanical failure of interconnects [35], degradation and cracking of the insulation [219], electrode corrosion [220, 221] and delamination of probe layers [222]. Biological failure mechanisms include initial tissue damage during insertion [34, 37]; breach of the blood–brain barrier [41]; elastic mismatch and tissue micromotion [35, 38, 39]; disruption of glial networks [40]; formation of a glial scar; and neuronal death associated with the abovementioned factors, as well as with materials neurotoxicity [42] and chemical mismatch [34].…”

Section: Figure 1│mentioning

confidence: 99%

Neural recording and modulation technologies

2017

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Within the mammalian nervous system, billions of neurons connected by quadrillions of synapses exchange electrical, chemical and mechanical signals. Disruptions to this network manifest as neurological or psychiatric conditions. Despite decades of neuroscience research, our ability to treat or even to understand these conditions is limited by the tools capable of probing the signalling complexity of the nervous system. Although orders of magnitude smaller and computationally faster than neurons, conventional substrate-bound electronics do not address the chemical and mechanical properties of neural tissue. This mismatch results in a foreign-body response and the encapsulation of devices by glial scars, suggesting that the design of an interface between the nervous system and a synthetic sensor requires additional materials innovation. Advances in genetic tools for manipulating neural activity have fuelled the demand for devices capable of simultaneous recording and controlling individual neurons at unprecedented scales. Recently, flexible organic electronics and bio- and nanomaterials have been developed for multifunctional and minimally invasive probes for long-term interaction with the nervous system. In this Review, we discuss the design lessons from the quarter-century-old field of neural engineering, highlight recent materials-driven progress in neural probes, and look at emergent directions inspired by the principles of neural transduction.

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Section: Figure 1│mentioning

confidence: 99%

Neural recording and modulation technologies

2017

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“…Previous studies [12] reported the formation of bubbles and delamination of thin Parylene-C films after just two days of soaking in saline solution. It is therefore important to investigate how the proposed plasma treatment influences the diffusion barrier properties of Parylene-C. For this purpose, a test setup similar to the one described by Op de Beeck et al [13] was used.…”

Section: Resultsmentioning

confidence: 99%

“…There are, however, reports of progressive degradation of the polymer insulation barrier properties when it is exposed to saline solution in a body-mimicking environment [12,13]. …”

Section: Introductionmentioning

confidence: 99%

Surface Nanostructuring of Parylene-C Coatings for Blood Contacting Implants

et al. 2018

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This paper investigates the effects on the blood compatibility of surface nanostructuring of Parylene-C coating. The proposed technique, based on the consecutive use of O2 and SF6 plasma, alters the surface roughness and enhances the intrinsic hydrophobicity of Parylene-C. The degree of hydrophobicity of the prepared surface can be precisely controlled by opportunely adjusting the plasma exposure times. Static contact angle measurements, performed on treated Parylene-C, showed a maximum contact angle of 158°. The nanostructured Parylene-C retained its hydrophobicity up to 45 days, when stored in a dry environment. Storing the samples in a body-mimicking solution caused the contact angle to progressively decrease. However, at the end of the measurement, the plasma treated surfaces still exhibited a higher hydrophobicity than the untreated counterparts. The proposed treatment improved the performance of the polymer as a water diffusion barrier in a body simulating environment. Modifying the nanotopography of the polymer influences the adsorption of different blood plasma proteins. The adsorption of albumin—a platelet adhesion inhibitor—and of fibrinogen—a platelet adhesion promoter—was studied by fluorescence microscopy. The adsorption capacity increased monotonically with increasing hydrophobicity for both studied proteins. The effect on albumin adsorption was considerably higher than on fibrinogen. Study of the proteins simultaneous adsorption showed that the albumin to fibrinogen adsorbed ratio increases with substrate hydrophobicity, suggesting lower thrombogenicity of the nanostructured surfaces. Animal experiments proved that the treated surfaces did not trigger any blood clot or thrombus formation when directly exposed to the arterial blood flow. The findings above, together with the exceptional mechanical and insulation properties of Parylene-C, support its use for packaging implants chronically exposed to the blood flow.

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“…Parylene suffers from poor adhesion to itself and noble metals, such as gold and platinum, a considerable drawback in the implementation of Parylene for bioMEMS. The adhesion of Parylene devices, which consist of thin films of Parylene-metal-Parylene sandwiches, is compromised when devices are soaked in wet environments [ 58 , 60 , 66 , 68 , 69 ]. Weak adhesion can accelerate catastrophic failure of Parylene devices; as Parylene films lift off a substrate, voids form in which water vapor can condense, creating continuous paths of solution that create electrical shorts and drive further delamination ( Figure 6 ).…”

Section: Challengesmentioning

confidence: 99%

Techniques and Considerations in the Microfabrication of Parylene C Microelectromechanical Systems

et al. 2018

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Parylene C is a promising material for constructing flexible, biocompatible and corrosion-resistant microelectromechanical systems (MEMS) devices. Historically, Parylene C has been employed as an encapsulation material for medical implants, such as stents and pacemakers, due to its strong barrier properties and biocompatibility. In the past few decades, the adaptation of planar microfabrication processes to thin film Parylene C has encouraged its use as an insulator, structural and substrate material for MEMS and other microelectronic devices. However, Parylene C presents unique challenges during microfabrication and during use with liquids, especially for flexible, thin film electronic devices. In particular, the flexibility and low thermal budget of Parylene C require modification of the fabrication techniques inherited from silicon MEMS, and poor adhesion at Parylene-Parylene and Parylene-metal interfaces causes device failure under prolonged use in wet environments. Here, we discuss in detail the promises and challenges inherent to Parylene C and present our experience in developing thin-film Parylene MEMS devices.

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Corrosion Behavior of Parylene-Metal-Parylene Thin Films in Saline

Cited by 42 publications

References 2 publications

Neural recording and modulation technologies

Neural recording and modulation technologies

Surface Nanostructuring of Parylene-C Coatings for Blood Contacting Implants

Techniques and Considerations in the Microfabrication of Parylene C Microelectromechanical Systems

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