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Attempts to apply artificial nano/micromotors for diverse biomedical applications have inspired a variety of strategies for designing motors with diverse propulsion mechanisms and functions. However, existing artificial motors are made exclusively of synthetic materials, which are subject to serious immune attack and clearance upon entering the bloodstream. Herein we report an elegant approach that turns natural red blood cells (RBCs) into functional micromotors with the aid of ultrasound propulsion and magnetic guidance. Iron oxide nanoparticles are loaded into the RBCs, where their asymmetric distribution within the cells results in a net magnetization, thus enabling magnetic alignment and guidance under acoustic propulsion. The RBC motors display efficient guided and prolonged propulsion in various biological fluids, including undiluted whole blood. The stability and functionality of the RBC motors, as well as the tolerability of regular RBCs to the ultrasound operation, are carefully examined. Since the RBC motors preserve the biological and structural features of regular RBCs, these motors possess a wide range of antigenic, transport, and mechanical properties that common synthetic motors cannot achieve and thus hold considerable promise for a number of practical biomedical uses.

Motion is a common phenomenon in biological processes. Major advances have been made in designing various self-propelled micromachines that harvest different types of energies into mechanical movement to achieve biomedicine and biological applications. Inspired by fascinating self-organization motion of natural creatures, the swarming or assembly of synthetic micro/nanomachines (often referred to micro/nanoswimmers, micro/nanorobots, micro/nanomachines, or micro/nanomotors), are able to mimic these amazing natural systems to help humanity accomplishing complex biological tasks. This review described the fuel induced methods (enzyme, hydrogen peroxide, hydrazine, et al.) and fuel-free induced approaches (electric, ultrasound, light, and magnetic) that led to control the assembly and swarming of synthetic micro/nanomachines. Such behavior is of fundamental importance in improving our understanding of self-assembly processes that are occurring on molecular to macroscopic length scales. [ABSTRACT FROM AUTHOR]

Reliably monitoring sweat volume has attracted much attention due to its important role in the assessment of physiological health conditions and the prevention of dehydration. Here, we present the first example of wearable strain sensor for real-time sweat volume monitoring. Such sweat volume monitoring sensor is simply fabricated via embedding strain sensing fabric in super-absorbent hydrogels, the hydrogels can wick sweat up off the skin surface to swell and then trigger the strain sensing fabrics response. This sensor can realize real-time detection of sweat volume (0.15-700 μL), shows excellent repeatability and stability against movement or light interference, reliability in the non-pathological range (pH: 4-9 and salinity: 0-100 mM NaCl) in addition. Such sensor combing swellable hydrogels with strain sensing fabrics provides a novel measurement method of wearable devices for sweat volume monitoring., Competing Interests: The authors declare no competing interests., (© 2020 The Author(s).)