Gastrointestinal (GI) pacing for stomach and intestines, analogous to cardiac pacing for heart, has been an emerging electrotherapy to entrain omnipresent bioelectrical activity and stimulate contraction of smooth muscle cells (SMCs), especially for patients who are refractory to medical therapy. Concurrent tracking of the electrical activities of SMCs and mechanical responses of the GI tract can offer essential and quantitative information to interpret and mitigate stimulated digestive processes. However, existing technologies for concurrent measurements of electrical and mechanical responses are still limited. The major limitations are the rigid nature of insertion electrodes and sensors, and the lack of highly stretchable and conformal platforms to accommodate the free-moving and stretchable nature of small and large intestines.
In this dissertation, an ultra-stretchable electronic rubber band, which we called e-band, has been demonstrated on slaughtered and neuroactive porcine small intestine segments for the functions of electrical stimulation, electromyography, and tissue motility recordings. The latter includes tissue impedance measurement and transmural pressure recordings.
The e-band was simply realized by one liquid-metal based strain sensor and two medical- grade stainless-steel electrodes compacted in five layers of ultra-thin silicone elastomer films. It was fabricated by the techniques of silicone thin film transfer, UV laser cutting, screen printing, and microfluidic filling in a fashion of low cost, fast turning rate, and clean-room free.
The e-band was pre-strained, wrapped around, and partially anchored on small intestine segments to form a closed loop. It was proved to be compliant to the GI tract. Electrical stimulation with various amplitudes of biphasic current pulses has induced different levels of contraction movement that was concurrently monitored by the strain sensor for transmural pressure recordings. Concurrent measurement of the electrical activity of SMCs and the mechanical movement of tissues has been demonstrated by the two stainless-steel electrodes for electromyography (EMG) and tissue impedance measurement, and the strain sensor for transmural pressure monitoring, respectively. Slow waves, spikes, and corresponding contraction movement of the SMCs have been observed in EMG and transmural pressure recordings.
In conclusion, an implantable, stretchable, and conformal GI neuromuscular stimulator with concurrent measurement of transient electrical and mechanical responses has been demonstrated on slaughtered and neuroactive porcine small intestine segments.
