Concentric, Mems-Based Optoelectromechanical Pacer for Multimodal Cardiac Excitation

This paper reports on the fabrication, assembly, characterization and validation of a novel opto-electrical cardiac stimulator designed to augment a mechanical pacing device. The integration of miniaturized electrodes and blue light-emitting diode (LED) chips on the pacer tip with a diameter of 1 mm enables the application of multimodal stimuli in one location on the surface of isolated murine hearts. The opto-electrical stimulator is based on two separate polyimide (PI) substrates each with a thickness of $10\ \mu \mathrm{m}$ combined into a functional unit based on dedicated assembly and encapsulation processes using silicone rubber. The experimental validation in isolated, whole hearts compares electrical, optical and mechanical stimuli exerted at frequencies of up to 8 Hz on Langen-dorff-perfused hearts expressing channelrhodopsin-2. The integrated iridium oxide electrodes implemented above the LED chips enable simultaneous electrical recordings of local cardiac electrical activity.