Cold Laser Micro-Machining of PDMS as an Encapsulation Layer for Soft Implantable Neural Interface

Abstract

PDMS (polydimethylsiloxane) is an important soft biocompatible material, which has various applications such as an implantable neural interface, a microfluidic chip, a wearable brain–computer interface, etc. However, the selective removal of the PDMS encapsulation layer is still a big challenge due to its chemical inertness and soft mechanical properties. Here, we use an excimer laser as a cold micro-machining tool for the precise removal of the PDMS encapsulation layer which can expose the electrode sites in an implantable neural interface. This study investigated and optimized the effect of excimer laser cutting parameters on the electrochemical impedance of a neural electrode by using orthogonal experiment design. Electrochemical impedance at the representative frequencies is discussed, which helps to construct the equivalent circuit model. Furthermore, the parameters of the equivalent circuit model are fitted, which reveals details about the electrochemical property of neural electrode using PDMS as an encapsulation layer. Our experimental findings suggest the promising application of excimer lasers in the micro-machining of implantable neural interface.

Biomimetic Exogenous “Tissue Batteries” as Artificial Power Sources for Implantable Bioelectronic Devices Manufacturing

“…[ 86 ] Currently, the most commonly used encapsulation materials include polyimide (PI), polydimethylsiloxane (PDMS), poly(tetrafluoroethylene) (PTFE), and chitosan, among others. [ 87 , 88 , 89 , 90 , 91 , 92 ] However, the selection of encapsulation materials needs to be considered from multiple perspectives, as the degradation performance and robustness requirements of the materials vary depending on specific application scenarios, such as short/long‐term or permanent implantation of electronic devices. [ 93 , 94 ]…”

State‐of‐the‐Art Electronic Materials for Thin Films in Bioelectronics

“…Microfabrication is complicated however as etching is difficult due to its chemical inertness and mechanical softness. [ 131 ] Its low surface energy is problematic for adhesion of deposited metal layers. This problem can be partly solved by chemical treatment or by thermal bonding when the PDMS is deposited on metallic layers.…”