Chronic Dielectric Performance of Parylene-modified Polydimethylsiloxane for Insulating Stretchable Electronics

This paper studies the long-term performance of parylene-modified polydimethylsiloxane (PDMS) as a stretchable dielectric material for biomedical applications. By employing electrochemical impedance spectroscopy (EIS), we continuously monitor the insulation capabilities of reference dielectric materials and two variations, including pristine parylene, parylene-shielded PDMS (ps-PDMS), parylene-caulked PDMS (pc-PDMS), and pristine PDMS within a high-conductivity fluid that mimics a physiological environment. We found that the dielectric performance of the parylene-modified PDMS displays distinct behaviors: the ps-PDMS exhibited improved dielectric properties, whereas the pc-PDMS showed even worse dielectric properties compared to pristine PDMS. To elucidate the observed degradation of various dielectric encapsulations due to ion percolation, a simple physical model based on equivalent circuit components was developed. Our model underscores the crucial role of a lateral ion barrier in ensuring effective insulation. This study offered valuable insights into the dependence of the dielectric properties of composite materials on fabrication techniques while shedding light on the inherent conflict between stretchability and electrical insulation.