Opto-ultrasonic communications for wireless intra-body nanonetworks

Wirelessly interconnected nanorobots, i.e., engineered devices of sizes ranging from one to a few hundred nanometers, are promising revolutionary diagnostic and therapeutic medical applications that could enhance the treatment of major diseases. Each nanorobot is usually designed to perform a set of basic tasks such as sensing and actuation. A dense wireless network of nano-devices, i.e., a nanonetwork, could potentially accomplish new and more complex functionalities, e.g., in-vivo monitoring or adaptive drug-delivery, thus enabling revolutionary nanomedicine applications.Several innovative communication paradigms to enable nanonetworks have been proposed in the last few years, including electromagnetic communications in the terahertz band, or molecular and neural communications. In this paper, we propose and discuss an alternative approach based on establishing intra-body opto-ultrasonic communications among nanorobots. Opto-ultrasonic communications are based on the optoacoustic effect, which enables the generation of high-frequency acoustic waves by irradiating the medium with electromagnetic energy in the optical frequency range. We first discuss the fundamentals of nanoscale opto-ultrasonic communications in biological tissues by modeling the generation, propagation and detection of opto-ultrasonic waves, and we explore important tradeoffs. Then, we discuss potential research challenges for the design of opto-ultrasonic nanonetworks of implantable devices at the physical, medium access control, and network layers of the protocol stack.