Ultrasound (US) is a promising modality for wirelessly powering implantable devices, requiring encapsulated receivers to ensure long-term stability. Traditional hermetic packaging often limits acoustic transmission, making polymer-based encapsulation a more suitable alternative. This study investigates how implant-grade polymers, thermoplastic polyurethane (TPU), parylene-C, and medical-grade silicones (MED-1000 and MED2-4213), affect the receive performance of piezoelectric micromachined ultrasonic transducers (PMUTs). Simulations and measurements between 1 and 7 MHz show that all tested materials exhibit transmission coefficients above 94% at nanometer- and micrometer-scale thicknesses, confirming their acoustic transparency. The results show that although coated PMUTs are acoustically well matched with the surrounding water medium, the added mechanical load of the coating can hinder membrane motion and reduce the energy transferred to the PMUTs. Modeling and experimental data demonstrate that stiffer coatings, such as parylene-C, lead to a reduced sensitivity when similar thicknesses are used. Likewise, residual stress in materials like MED-1000 can also degrade the performance. These effects are not evident from acoustic transmission measurements alone, underscoring the need to assess both acoustic and mechanical properties when selecting encapsulation materials. In general, softer materials offer excellent acoustic performance for PMUT encapsulation, while stiffer materials must be applied in thinner layers to avoid impairing PMUT function.

Recording neuronal activity triggered by electrical impulses is a powerful tool in neuroscience research and neural engineering. It is often applied in acute electrophysiological experimental settings to record compound nerve action potentials. However, the elicited neural response is often distorted by electrical stimulus artifacts, complicating subsequent analysis. In this work, we present a model to better understand the effect of the selected amplifier configuration and the location of the ground electrode in a practical electrophysiological nerve setup. Simulation results show that the stimulus artifact can be reduced by more than an order of magnitude if the placement of the ground electrode, its impedance, and the amplifier configuration are optimized. We experimentally demonstrate the effects in three different settings, in-vivo and in-vitro.

Over the past decades, neuromodulation has been proven to be an effective treatment for several neurological disorders. Moreover, it continues to be a rapidly evolving field with a wide-ranging potential for biomedical applications. However, efficient and patient-specific targeted neuromodulation remains one of the biggest challenges for implantable devices. Current studies explore the possibility of using multimodal neuromodulation techniques by combining electrical, thermal, optical, ultrasonic, and/or pharmacological methods to increase the specificity of therapies.1 Moreover, it is hypothesized that the safety profiles and spatiotemporal resolution could potentially increase by combining electrical and ultrasonic methods into a hybrid neuromodulation technique.2 Low-intensity focused ultrasound has the potential to alter the neural response in a wide range of neuronal targets, with an improved spatial resolution.3,4 However, the most effective, reliable, and safe acoustic parameters are currently unknown, especially for the peripheral nervous system, due to the little understanding of the mechanisms that govern this method.5 In this study, we propose an investigational platform that will allow us to explore a variety of ultrasound parameters for a multimodal neuromodulation approach. The platform integrates a custom- adapted system for stimulation and neural recording, commercially available components for the ultrasound stimulation system, and an experimental control unit with a PC interface. The proposed setup facilitates the evaluation of the tested parameters during experiments on explanted nerve models. Here we will describe potential implementations of such a system and discuss challenges that can be faced during experiments on explanted nerves. This work can be useful to increase our understanding of ultrasound neuromodulation on peripheral nerves and its benefits when integrated into a hybrid platform dedicated to multimodal neuromodulation.