Reliability of Protective Coatings for Flexible Piezoelectric Transducers in Aqueous Environments

Abstract

Electronic devices used for marine applications suffer from several issues that can compromise their performance. In particular, water absorption and permeation can lead to the corrosion of metal parts or short-circuits. The added mass due to the absorbed water affects the inertia and durability of the devices, especially for flexible and very thin micro-systems. Furthermore, the employment of such delicate devices underwater is unavoidably subjected to the adhesion of microorganisms and formation of biofilms that limit their reliability. Thus, the demand of waterproofing solutions has increased in recent years, focusing on more conformal, flexible and insulating coatings. This work introduces an evaluation of different polymeric coatings (parylene-C, poly-dimethyl siloxane (PDMS), poly-methyl methacrylate (PMMA), and poly-(vinylidene fluoride) (PVDF)) aimed at increasing the reliability of piezoelectric flexible microdevices used for sensing water motions or for scavenging wave energy. Absorption and corrosion tests showed that Parylene-C, while susceptible to micro-cracking during prolonged oscillating cycles, exhibits the best anti-corrosive behavior. Parylene-C was then treated with oxygen plasma and UV/ozone for modifying the surface morphology in order to evaluate the biofilm formation with different surface conditions. A preliminary characterization through a laser Doppler vibrometer allowed us to detect a reduction in the biofilm mass surface density after 35 days of exposure to seawater.

Smart Textiles Testing: A Roadmap to Standardized Test Methods for Safety and Quality-Control

“…Embedded electronics in e-textiles may suffer from short-circuits or mechanical failures, e.g. due to body sweat or ambient moisture, similarly to what is observed for electronic devices in marine environments [49]. Such malfunctioning can cause serious health hazards or fire accidents.…”

“…Besides the possibility of electric shocks or complete signal loss from corrosion, marine e-textiles could also experience decreased efficiency when exposed to the salt of seawater. As soon as the saltwater propagates the localized corrosion process of textile electrodes or conductive interconnects, it could affect the overall signal quality, lowering the transduction efficiency [49].…”

Conformal, Ultra‐thin Skin‐Contact‐Actuated Hybrid Piezo/Triboelectric Wearable Sensor Based on AlN and Parylene‐Encapsulated Elastomeric Blend

“…In this work parylene C (poly(para‐xylylene)) was selected because of its attractive properties, [ 73,74 ] such as FDA‐approved biocompatibility, chemical inertness, optimal conformality, barrier properties, anticorrosive/antibiofouling behavior, and high flexibility. [ 75–80 ] It can be easily deposited through an efficient, room‐temperature, controlled process (Gorham route) [ 81 ] and it can also be variously surface‐treated, for example, under oxygen plasma, ozonized UV, or by wet and dry etching processes. [ 75,82,83 ]…”

A Novel Accelerated Corrosion Test for Supporting Devices in a Floating Photovoltaic System

“…The corrosion tests of various structural materials (aluminum or coated steels) used in PV structures are conducted by exposing them to the sea, and the durability of materials is periodically evaluated according to the extent of corrosion [8]. Four anti-corrosion approaches can be applied in a marine environment [9], and four different polymeric coatings on 314 SS are introduced to prevent corrosion for marine applications [10]. Nevertheless, this test method takes an enormous amount of time.…”