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.

Objective. Finite element modelling has been widely used to understand the effect of stimulation on the nerve fibres. Yet the literature on analysis of spontaneous nerve activity is much scarcer. In this study, we introduce a method based on a finite element model, to analyse spontaneous nerve activity with a typical bipolar electrode recording setup, enabling the identification of spontaneously active fibres. We applied our method to the vagus nerve, which plays a key role in refractory epilepsy. Approach. We developed a 3D model including dynamic action potential propagation, based on the vagus nerve geometry. The impact of key recording parametersinter-electrode distance and temperatureand uncontrolled parametersfibre size and position in the nerveon the ability to discriminate active fibres were quantified. A specific algorithm was implemented to detect and classify action potentials from recordings, and tested on six rat in-vivo vagus nerve recordings. Main results. Fibre diameters can be discriminated if they are below 3 µm and 7 µm, respectively for inter-electrode distances of 2 mm and 4 mm. The impact of the position of the fibre inside the nerve on fibre diameter discrimination is limited. The range of active fibres identified by modelling in the vagus nerve of rats is in agreement with ranges found at histology. Significance. The nerve fibre diameter, directly proportional to the action potential propagation velocity, is related to a specific physiological function. Estimating the source fibre diameter is thus essential to interpret neural recordings. Among many possible applications, the present method was developed in the context of a project to improve vagus nerve stimulation therapy for epilepsy.

Gastrointestinal stimulator implants have recently shown promising results in helping obese patients lose weight. However, to place the implant, the patient currently needs to undergo an invasive surgical procedure. We report a less invasive procedure to stimulate the stomach with a gastrostimulator. After attempting fully endoscopic implantation, we more recently focused on a single incision percutaneous procedure. In both cases, the challenges in electronic design of the implant are largely similar. This article covers the work achieved to meet these and details the in vivo validation of a gastrostimulator aimed to be endoscopically placed and anchored to the stomach.

Gastrointestinal stimulator implants have recently shown positive results in helping obese patients lose weight. However, to place the implant, the patient currently needs to undergo an invasive surgical procedure. Our team is aiming for a less invasive procedure to stimulate the stomach with a gastrostimulator. Attempts covered fully endoscopic implantation and, more recently, we have focussed on a single incision laparoscopic procedure. Whatever the chosen implantation solution, the electronic design of the implant system shares many challenges. This paper covers the work achieved to meet these.

Cross-talk phenomena should be avoided when stimulating nerves. One option to limit the current spread is to use tripolar electrodes, but at the cost of increasing the number of wires connection. This should be avoided since cables must be thin and compliant. We investigated the impact of the central electrode position and of current spread due to a gap between book and lid on cross-talk, in a set of tripolar or quasi-tripolar configurations..