Evaluation of Commercial Connectors for Active Neural Implants.

Multichannel connectors enable part-replacement of implanted active neural interfaces. For pre-clinical investigation, commercially available miniature connectors enable high channel counts with reduced size and cost. In this paper, Omnetics Nano Circular connectors were encapsulated with medical grade silicone, and assembled using an approach proposed used in surgery. Three 11-pin connectors were tested in PBS for 336 days with cyclic loading for a total of 66 days. A single connector failed with current leakage between channels due to moisture at the connecting interface, and with corrosion at 3 solder joints. The surviving connectors maintained a low contact impedance and high between-channel impedance over 336 days. Inspection of the failed sample emphasizes the need for stress relief near implanted connectors and void-free encapsulation

Silicone rubber encapsulation for an endoscopically implantable gastrostimulator.

Gastrointestinal stimulator implants have recently shown positive results in treating obesity. However, the implantation currently requires an invasive surgical procedure. Endoscopy could be used to place the gastric stimulator in the stomach, hence avoiding the riskier surgery. The implant then needs to go through the oesophagus and be located inside the stomach, which imposes new design constraints, such as miniaturization and protecting the electronic circuit against the highly acidic environment of the stomach. We propose to protect the implant by encapsulation with silicone rubber. This paper lists the advantages of this method compared to the more usual approach of a hermetic enclosure and then presents a method to evaluate the underwater adhesive stability of six adhesive/substrate couples, using repeated lap-shear tests and an elevated temperature to accelerate the ageing process. The results for different adhesive/substrate couples tested, presented on probability plots, show that FR4 and alumina substrates with MED4-4220 silicone rubber are suitable for a first implantable prototype. We then compare these with the predicted lifetimes of bonds between historical standard silicone rubber DC3140 and different substrates and describe the encapsulation of our gastrostimulator.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

A Study of Techniques and Mechanisms of Vagus Nerve Stimulation for Treatment of Inflammation

Vagus nerve stimulation (VNS) has been on the forefront of inflammatory disorder research for the better part of the last three decades and has yielded many promising results. There remains, however, much debate about the actual biological mechanisms of such treatments, as well as, questions about inconsistencies in methods used in many research efforts. In this work, I identify shortcomings in past VNS methods and submit new developments and findings that can progress the research community towards more selective and relevant VNS research and treatments. In Aim 1, I present the most recent advancements in the capabilities of our fully implantable Bionode stimulation device platform for use in VNS studies to include stimulation circuitry, device packaging, and stimulation cuff design. In Aim 2, I characterize the inflammatory cytokine response of rats to intraperitoneally injected endotoxin utilizing new data analysis methods and demonstrate the modulatory effects of VNS applied by the Bionode stimulator to subdiaphragmatic branches of the left vagus nerve in an acute study. In Aim 3, using fully implanted Bionode devices, I expose a previously unidentified effect of chronically cuffing the left cervical vagus nerve to suppress efferent Fluorogold transport and cause unintended attenuation to physiological effects of VNS. Finally, in accordance with our findings from Aims 1, 2, and 3, I present results from new and promising techniques we have explored for future use of VNS in inflammation studies