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Reliability and lifetime estimation of implantable medical devices (IMDs) is one of the essential steps in their design and development. As any failure of IMDs can result in serious health risks for the patients, they should be guaranteed not to fail over their intended lifetime under the harsh body fluidic and chemical environments. Traditional leak tests are applicable to large cm‐scale IMDs, and they are often destructive, laborious, and costly. This paper presents an automated and wireless accelerated heat soak testing system to assess hermetic failure mechanisms in small mm‐sized inductively powered IMDs. A high‐throughput readout coil array printed circuit board can test hermeticity of multiple mm‐sized wireless IMDs simultaneously in a harsh environment (e.g., 45 °C/90% RH with an error range of ±0.2% for 18 days gage repeatability and reproducibility test). An accelerated heat soak test is performed to evaluate the electronic durability and estimate the lifetime of the IMDs. This work focuses on validating the proposed system interrogating with eight inductor–capacitor sensors, composed of an interdigitated capacitive sensor connected to an inductor patterned polyimide substrate, to examine hermetic failure mechanisms of parylene‐C encapsulation for wireless IMDs as well as broader miniature‐sized consumer electronics.

We introduce a single channel neuro-stimulator consisting of a reflector-coupled microscale light emitting diode (µLED) with an integrated mm-sized wireless receiver (Rx) coil for free-floating, battery-free, untethered optogenetics neuromodulation. The system utilizes a two-coil inductive link to deliver instantaneous power at a low operating frequency (<100 MHz) for continuous optical stimulation with minimized invasiveness and tissue exposure to electromagnetic radiation. Coupling a microscale reflector to the µLED provides significant light intensity enhancement compared to a bare µLED. Our activated stimulators have an operational temperature increase of <1 °C, well below the safety limit of biomedical implants. In vivo experiment and histological analysis verify the efficacy of wireless optical stimulation in the primary visual cortex of rats, using c-Fos biomarker as a reporter of light-evoked neuronal activity.