This paper reports on the characterization of a microfabricated wafer-scale, graphene-based, soft implant for spinal cord applications. Graphene is used because of its high transparency and good conductivity, making it suitable for optogenetic applications. Moreover it has a high mechanical strength and is potentially biocompatible. The implant consists of multi-layered chemical vapor deposited graphene, in the form of electrodes and tracks, encapsulated between 2 layers of silicone. Methods such as Raman spectroscopy, optical transmittance, and electrical measurements combined with bending tests and in-vitro experiments, using phosphate-buffered saline (PBS) solution, were employed to characterize the device. The results have shown high bendability and no critical damage of the graphene after immersing the device in PBS solution up to 7 days. To the authors' best knowledge, this is the first work that presents a soft and fully scalable optogenetics-compatible graphene-based spinal cord electrode array.

2D phased array ultrasonic transducers realized through the combination of bulk piezoelectric ceramics and complementary metal-oxide-semiconductor (CMOS) integrated circuits (IC) are enabling a new range of wearable ultrasound therapeutic applications. Traditional therapeutic ultrasound transducers have an air backing layer to maximize transmitted acoustic intensity. Yet, the pairing of piezoelectric transducers and silicon substrates commonly used in CMOS is still poorly understood. We integrated lead zirconate titanate (PZT) film on silicon membranes of various thicknesses to understand the impact of the silicon backing on the performance of bulk piezoelectric ultrasound transducers. The transducers with thinner silicon membranes exhibited higher acoustic intensity (up to 1.95 times while taking into account frequency shift), which is consistent with the simulation in finite element modeling. Transducers with silicon substrate also demonstrated a consistent shift to a higher resonance frequency.