The influence of thermal history on structure and water transport in Parylene C coatings

Davis, Eric M.; Benetatos, Nicholas M.; Regnault, W. F.; Winey, Karen I.; Elabd, Yossef A.

doi:10.1016/j.polymer.2011.08.010

Cited by 62 publications

(52 citation statements)

References 29 publications

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“…The drop at low frequencies might be due to delamination of insulation from the electrode metal surface or moisture penetrating through the Parylene-C, causing a switch from a more capacitive to a more resistive conductivity mode which is manifested as an increase in the phase angle at low frequency. Davis et al described such moisture diffusion in Parylene-C (Davis et al 2011). Furthermore, water diffusion through parylene leads to an increase in dielectric permittivity and capacitive coupling through the insulation (Seymour et al 2009).…”

Section: Impact Of the Raamentioning

confidence: 99%

Rapid evaluation of the durability of cortical neural implants using accelerated aging with reactive oxygen species

et al. 2015

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Objective-A challenge for implementing high bandwidth cortical brain-machine interface devices in patients is the limited functional lifespan of implanted recording electrodes. Development of implant technology currently requires extensive non-clinical testing to demonstrate device performance. However, testing the durability of the implants in vivo is timeconsuming and expensive. Validated in vitro methodologies may reduce the need for extensive testing in animal models.Approach-Here we describe an in vitro platform for rapid evaluation of implant stability. We designed a reactive accelerated aging (RAA) protocol that employs elevated temperature and reactive oxygen species (ROS) to create a harsh aging environment. Commercially available microelectrode arrays (MEAs) were placed in a solution of hydrogen peroxide at 87 °C for a period of 7 days. We monitored changes to the implants with scanning electron microscopy and broad spectrum electrochemical impedance spectroscopy (1 Hz-1 MHz) and correlated the physical changes with impedance data to identify markers associated with implant failure.Main results-RAA produced a diverse range of effects on the structural integrity and electrochemical properties of electrodes. Temperature and ROS appeared to have different effects on structural elements, with increased temperature causing insulation loss from the electrode microwires, and ROS concentration correlating with tungsten metal dissolution. All array types experienced impedance declines, consistent with published literature showing chronic (>30 days) declines in array impedance in vivo. Impedance change was greatest at frequencies <10 Hz, and smallest at frequencies 1 kHz and above. Though electrode performance is traditionally characterized by impedance at 1 kHz, our results indicate that an impedance change at 1 kHz is not a reliable predictive marker of implant degradation or failure.Significance-ROS, which are known to be present in vivo, can create structural damage and change electrical properties of MEAs. Broad-spectrum electrical impedance spectroscopy

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Section: Impact Of the Raamentioning

confidence: 99%

Rapid evaluation of the durability of cortical neural implants using accelerated aging with reactive oxygen species

et al. 2015

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“…• C), the amorphous regions of the polymer gain energy to rearrange, allowing for softening of the polymer and subsequent molecular relaxation and reorganization of the chains [29,31]. In thermoforming experiments, the soak temperature was not increased beyond the melting point to avoid device or film complications due to large and potentially damaging changes to the material properties following treatment above that temperature [32].…”

Section: Thermoforming Parylenementioning

confidence: 99%

“…An analysis of the sample surfaces conducted using contact angle measurements indicated no significant changes to the surface energy of Parylene as a function of either soak temperature or time (table 3, 4). Samples thermoformed [30], as well as the formation of a new second crystalline phase [29]. Variation of soak temperature had a larger effect on mechanical stiffness changes (increased 37%) largely due to the additional energy in the system at greater temperatures leading to increased reorganization and crystalline ordering of the polymer (table 3; one-way ANOVA: p < 0.0001; test for linear trend: p < 0.0001).…”

Section: Chemical and Surface Characterizationmentioning

confidence: 99%

“…This is achieved without the need for applied bonding pressures. In addition to the formation of a 3D shape, the final device also attains added benefits attributed to the annealing of Parylene layers, such as increased adhesion [28], decreased water permeability and increased dielectric strength [29], and improvement in thermal stability at higher temperatures, namely >37…”

Section: Introductionmentioning

confidence: 99%

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Formation of three-dimensional Parylene C structures via thermoforming

Kim

Chen

Gupta

et al. 2014

J. Micromech. Microeng.

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The thermoplastic nature of Parylene C is leveraged to enable the formation of three-dimensional structures using a thermal forming (thermoforming) technique. Thermoforming involves the heating of Parylene films above its glass transition temperature while they are physically confined in the final desired conformation. Micro and macro scale three-dimensional structures composed of Parylene thin films were developed using the thermoforming process, and the resulting chemical and mechanical changes to the films were characterized. No large changes to the surface and bulk chemistries of the polymer were observed following the thermoforming process conducted in vacuum. Heat treated structures exhibited increased stiffness by a maximum of 37% depending on the treatment temperature, due to an increase in crystallinity of the Parylene polymer. This study revealed important property changes resulting from the process, namely (1) the development of high strains in thermoformed areas of small radii of curvature (30-90 µm) and (2) ∼1.5% bulk material shrinkage in thermoformed multilayered Parylene-Parylene and Parylene-metal-Parylene films. Thermoforming is a simple process whereby three-dimensional structures can be achieved from Parylene C-based thin film structures with tunable mechanical properties as a function of treatment temperature.

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“…To validate our assumption about the grafting mechanism, we had to ascertain that adsorption of TEOS to parylene C film does indeed occur [21]. The thermal behavior of parylene C film incubated with TEOS (see Experimental section) and that of the pure parylene C film was thus compared by means of differential scanning calorimetry (DSC, see supporting information), HR-SEM, and compositional EDAX analysis (Fig.…”

Section: The Grafting Mechanismmentioning

confidence: 99%

A simple one-step approach to the decoration of parylene C coatings using functional silica-based NPs

Binyamini

Boguslavsky

Laux

et al. 2015

Surface and Coatings Technology

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The influence of thermal history on structure and water transport in Parylene C coatings

Cited by 62 publications

References 29 publications

Rapid evaluation of the durability of cortical neural implants using accelerated aging with reactive oxygen species

Rapid evaluation of the durability of cortical neural implants using accelerated aging with reactive oxygen species

Formation of three-dimensional Parylene C structures via thermoforming

A simple one-step approach to the decoration of parylene C coatings using functional silica-based NPs

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