The study of neurons is fundamental for basic neuroscience research and treatment of neurological disorders. In recent years ultrasound has been increasingly recognized as a viable method to stimulate neurons. However, traditional ultrasound transducers are limited in the scope of their application by self-heating effects, limited frequency range and cavitation effects during neuromodulation. In contrast, surface acoustic wave (SAW) devices, which are producing wavemodes with increasing application in biomedical devices, generate less self-heating, are smaller and create less cavitation. SAW devices thus have the potential to address some of the drawbacks of traditional ultrasound transducers and could be implemented as miniaturized wearable or implantable devices. In this mini review, we discuss the potential mechanisms of SAW-based neuromodulation, including mechanical displacement, electromagnetic fields, thermal effects, and acoustic streaming. We also review the application of SAW actuation for neuronal stimulation, including growth and neuromodulation. Finally, we propose future directions for SAW-based neuromodulation.

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Owing to several key attributes, diamond is an attractive candidate material for neural interfacing electrodes. The emergence of additivemanufacturing (AM) of diamond-based materials has addressed multiple challenges associated with the fabrication of diamond electrodes using the conventional chemical vapor deposition (CVD) approach. Unlike the CVD approach, AM methods have enabled the deposition of three-dimensional diamond-based material at room temperature. This work demonstrates the feasibility of using laser metal deposition to fabricate diamond−titanium hybrid electrodes for neuronal interfacing. In addition to exhibiting a high electrochemical capacitance of 1.1 mF cm −2 and a low electrochemical impedance of 1 kΩ cm 2 at 1 kHz in physiological saline, these electrodes exhibit a high degree of biocompatibility assessed in vitro using cortical neurons. Furthermore, surface characterization methods show the presence of an oxygenrich mixed-phase diamond−titanium surface along the grain boundaries. Overall, we demonstrated that our unique approach facilitates printing biocompatible titanium−diamond site-specific coating-free conductive hybrid surfaces using AM, which paves the way to printing customized electrodes and interfacing implantable medical devices.

Excitation using surface acoustic waves (SAW) has demonstrated efficacy in improving microscale particle/chemical transport due to its ability to generate microscale wavelengths. However, the effects of acoustic stimulation on transport processes along the length of sub-wavelength microchannels and their underlying mechanisms, essential for long-range transport, have not been examined in detail. In this work, we investigate diffusion along the length of subwavelength microchannels using experimental and simulation approaches, demonstrating enhanced transport under SAW excitation. The microchannel-based enhanced diffusion mechanisms are further studied by investigating the acoustic pressure and streaming fields, finding that the degree of enhancement is a function of applied power and microchannel dimensions. This microchannel-based diffusion enhancement approach is applicable to microfluidic and biomedical microscale transport enhancement, with the findings here being relevant to acoustic-based micro-mixing and neurodegenerative therapies.