Characterization of a Thiol-Ene/Acrylate-Based Polymer for Neuroprosthetic Implants

Abstract

Thiol-ene/acrylate shape-memory polymers can be used as base substrates for neural electrodes to treat neurological dysfunction. Neural electrodes are implanted into the body to alter or record impulse conduction. This study characterizes thiol-ene/acrylate polymers to determine which synthesis methods constitute an ideal substrate for neural implants. To achieve a desired Tg between 50 and 56.5 °C, curing conditions, polymer thickness, monomer ratios, and water uptake were all examined and controlled for. Characterization with dynamic mechanical analysis and thermal gravimetric analysis reveals that thin, thiol-ene/acrylate polymers composed of at least 50 mol % acrylate content and cured for at least 1 h at 365 nm are promising as substrates for neural electrodes.

Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface

“…Another consideration has been the characterization of the electrochemical interface, where Faradaic reactions have required careful consideration to avoid the generation of harmful reactive species and hydrogen/oxygen gasses [ 55 , 56 ]. Finally, a recent focus has been on material hardness and flexibility as there has been evidence showing that a mismatch between the mechanics of the material and soft tissues which are in constant micromotion has generated additional biological damage [ 47 , 48 , 57 ]. For clarity it should be noted that the all-SiC concept presented here does not address the micromotion issue.…”

Microfabricated Probes for Studying Brain Chemistry: A Review

“…Choices of traditional soft materials included polyimide, SU‐8, parylene, and polydimethylsiloxane (PDMS). Emerging polymer materials, namely shape memory polymers, have also gained attention in recent years due to their capability to adjust Young's modulus based on temperature changes . Therefore, these substrates may be tailored to be sufficiently stiff during probe insertion and softened inside the tissue.…”

“…Emerging polymer materials, namely shape memory polymers, have also gained attention in recent years due to their capability to adjust Young's modulus based on temperature changes. [133][134][135] Therefore, these substrates may be tailoredt ob es ufficiently stiff during probe insertion and softened inside the tissue.D espite the potential benefito fs oft implants, they are generally designed for primary use at the brain surface, or at depths up to af ew millimeters. Otherwise, soft implants normally require the use of needle guide or stiff coating (such as polyethylene glycol (PEG) [136,137] or biodegrad- Figure 2.…”

Softening Shape Memory Polymer Substrates for Bioelectronic Devices With Improved Hydrolytic Stability

“…However, after implantation, materials that soften to a modulus that is much closer to the tissue modulus offer the promise of decreasing the foreign body response and micromotion effects. Previously, the Voit Lab has presented a new generation of neural implants comprising of softening thiol-ene/acrylate polymers used as substrates (Ware et al, 2013(Ware et al, , 2014Do et al, 2017;Ecker et al, 2017;Simon et al, 2017). These devices work well for acute experiments and for chronic experiments on the order of 1-3 months.…”

“…Here, we present a thiol-ene SMP formulation that is chemically and structurally similar to the most recent ones, but does not contain any ester groups (Do et al, 2017;Ecker et al, 2017;Simon et al, 2017;Garcia-Sandoval et al, 2018;Shoffstall et al, 2018). We have optimized the synthesis of a new monomer and tailored the polymer composition to have similar in vivo softening capabilities as previous reported SMPs.…”