Translational prospects of untethered medical microrobots

Abstract

Untethered mobile microrobots have the potential to transform medicine radically. Their small size and wireless mobility can enable access to and navigation in confined, small, hard-to-reach, and sensitive inner body sites, where they can provide new ways of minimally invasive interventions and targeted diagnosis and therapy down to the cellular length scales with high precision and repeatability. The exponential recent progress of the field at the preclinical level raises anticipations for their near-future clinical prospects. To pave the way for this transformation to happen, however, the formerly proposed microrobotic system designs need a comprehensive review by including essential aspects that a microrobot needs to function properly and safely in given in vivo conditions of a targeted medical problem. The present review provides a translational perspective on medical microrobotics research with an application-oriented, integrative design approach. The blueprint of a medical microrobot needs to take account of microrobot shape, material composition, manufacturing technique, permeation of biological barriers, deployment strategy, actuation and control methods, medical imaging modality, and the execution of the prescribed medical tasks altogether at the same time. The incorporation of functional information pertaining each such element to the physical design of the microrobot is highly dependent on the specific clinical application scenario. We discuss the complexity of the challenges ahead and the potential directions to overcome them. We also throw light on the potential regulatory aspects of medical microrobots toward their bench-to-bedside translation. Such a multifaceted undertaking entails multidisciplinary involvement of engineers, materials scientists, biologists and medical doctors, and bringing their focus on specific medical problems where microrobots could make a disruptive or radical impact.

Pros and Cons: Magnetic versus Optical Microrobots

“…Compatibility of microrobots to their operation environment is essential for a given specific application. As one of the main challenges in this requirement for medical applications, microrobot materials must be biocompatible to use them inside the human body for short or long durations 6. Moreover, biodegradability would be an important another material requirement of the microrobot body in such application scenarios, if the microrobots cannot be removed from the body naturally or by catheter type of medical devices.…”

“…Mobile microrobotics has emerged as a new robotics field within the last decade to create untethered tiny robots that can access and operate in unprecedented, dangerous or hard‐to‐reach small spaces noninvasively toward disruptive medical, biotechnology, desktop manufacturing, environmental remediation, and other potential applications 1–7. Such field has many scientific challenges related to miniaturization limitations on on‐board actuation, powering, sensing, communication, computing, and application‐specific functions.…”

The Future Application of Organ-on-a-Chip Technologies as Proving Grounds for MicroBioRobots

“…This hemodynamic flow is driven primarily by the heart’s pumping action and regulated by complex cardiovascular mechanisms. When the goal is to precisely target a microscale payload, such as an MBR, to a specific tissue location in the body ( Figure 3 A), the cardiovascular fluid dynamics can pose a significant hurdle [ 34 ]. In particular, as the characteristic diameter of the flow reduces in the transition from large arteries to, ultimately, microscale capillaries, the flow becomes strictly laminar.…”

“…This review envisions MBRs as drug-laden delivery vehicles ( Figure 4 A). For these drugs to move from the MBR and enter a tissue, they must cross the hemorheological, fluidic barriers found in the vessel, penetrate the endothelium, and diffuse into the surrounding tissue [ 34 ]. Fortuitously, several organ-on-a-chip systems have been engineered to understand drug transport across these different barriers at the microscale.…”

RectMag3D: A Magnetic Actuation System for Steering Milli/Microrobots Based on Rectangular Electromagnetic Coils

“…Passive actuation that relies on direct interaction with the environmental media in the human body, such as early capsule robots move to rely on gastrointestinal peristalsis, is clearly not applicable to the field of minimally invasive diagnosis due to its inefficiency and difficulty in control. Wireless external field energized active actuation is currently the most suitable remote control method including magnetic actuation, electric actuation, microwave actuation, laser actuation, and ultrasonic wave actuation [5]. Compared with other external field energy sources, magnetic actuation has been proven safer and easier to control in the experimental environment because the magnetic field is capable of response in a short period and only has an influence on the magnetic medium placed therein [6].…”