Mechanisms and Applications of Neuromodulation Using Surface Acoustic Waves—A Mini-Review

Abstract

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.

Non-invasive transcranial ultrasound stimulation for neuromodulation

“…While there is no published evidence yet of ultrasound stimulation causing this mixing, the study showed that shear force generated by flowing solution over cultured cells produces substantial mixing (Petersen et al, 2016). This could be indirectly compared to compression force and resulting shear waves or more directly with acoustic streaming which may also play a role in ultrasound neuromodulation (Peng et al, 2021). The channels responsible for transduction of mechanical force into neural activity are under fierce investigation.…”

Open Source Board Based Acoustofluidic Transwells for Reversible Disruption of the Blood-Brain Barrier for Therapeutic Delivery

“…Other ways that disrupted BBB were possibly electromagnetic elds, thermal effects, and acoustic streaming [44]. Local excessive heating generated by SAWs might change the state of the cells [45], and cell shapes were believed to affect under periodic acoustic streaming by SAW excitation [46].…”

Acoustofluidics – changing paradigm in tissue engineering, therapeutics development, and biosensing

“…Moreover, miniaturization allows to focus or amplify the acoustic effects without drawbacks in large-scale systems such as self-heating and cavitation by offering a well-controlled domain. 141 Martinez Villegas et al 142 demonstrated the enhancement of the osteogenic differentiation and proliferation of adiposederived stem cells embedded into a photocurable hydrogel via acoustic patterning using a frequency of 13.11 MHz (SSAW). Furthermore, Devendran et al 143 scrutinized the phenotypes of four distinct human and mouse cell lines after exposure to 48.5 MHz (SAW).…”

“…They observed that the neurite outgrowth was preferentially aligned to the axis of the SSAW pressure nodal lines, 145 which suggests the possibility of the cytoskeleton or the ECM realignment by acoustic waves. 141 The mechanical stimulation of cells by ultrasound waves in low frequency and conventional systems has shown various effects such as the increase in production of IL-8, VEGF, and bFG, with a 112% surge in collagen synthesis and a 35-52% increase in the proliferation rate of fibroblasts and osteoblasts. 146 Stamp et al 39 scrutinized the mechanical stimulations, along with electrical triggers that might be present in SAW platforms.…”