Size-Dependent Locomotion Ability of Surface Microrollers on Physiologically Relevant Microtopographical Surfaces

Roadmap for Clinical Translation of Mobile Microrobotics

Medical microrobotics is an emerging field to revolutionize clinical applications in diagnostics and therapeutics of various diseases. On the other hand, the mobile microrobotics field has important obstacles to pass before clinical translation. This article focuses on these challenges and provides a roadmap of medical microrobots to enable their clinical use. From the concept of a "magic bullet" to the physicochemical interactions of microrobots in complex biological environments in medical applications, there are several translational steps to consider. Clinical translation of mobile microrobots is only possible with a close collaboration between clinical experts and microrobotics researchers to address the technical challenges in microfabrication, safety, and imaging. The clinical application potential can be materialized by designing microrobots that can solve the current main challenges, such as actuation limitations, material stability, and imaging constraints. The strengths and weaknesses of the current progress in the microrobotics field are discussed and a roadmap for their clinical applications in the near future is outlined.

Janus microparticles-based targeted and spatially-controlled piezoelectric neural stimulation via low-intensity focused ultrasound

Electrical stimulation is a fundamental tool in studying neural circuits, treating neurological diseases, and advancing regenerative medicine. Injectable, free-standing piezoelectric particle systems have emerged as non-genetic and wireless alternatives for electrode-based tethered stimulation systems. However, achieving cell-specific and high-frequency piezoelectric neural stimulation remains challenging due to high-intensity thresholds, non-specific diffusion, and internalization of particles. Here, we develop cell-sized 20 μm-diameter silica-based piezoelectric magnetic Janus microparticles (PEMPs), enabling clinically-relevant high-frequency neural stimulation of primary neurons under low-intensity focused ultrasound. Owing to its functionally anisotropic design, half of the PEMP acts as a piezoelectric electrode via conjugated barium titanate nanoparticles to induce electrical stimulation, while the nickel-gold nanofilm-coated magnetic half provides spatial and orientational control on neural stimulation via external uniform rotating magnetic fields. Furthermore, surface functionalization with targeting antibodies enables cell-specific binding/targeting and stimulation of dopaminergic neurons. Taking advantage of such functionalities, the PEMP design offers unique features towards wireless neural stimulation for minimally invasive treatment of neurological diseases.

Multi-level magnetic microrobot delivery strategy within a hierarchical vascularized organ-on-a-chip

Targeted microrobotic delivery within the circulatory system holds significant potential for medical theranostic applications. Existing delivery strategies of microrobots encounter challenges such as slow speed, limited navigation control, and dispersal under dynamic flow conditions. Furthermore, within the realm of microrobots, in vitro testing platforms often lack essential biological microenvironments, while in vivo studies conducted on animal models are constrained by limited detection resolution. In this study, we propose a multi-level magnetic delivery strategy that integrates a tethered microrobotic guidewire and untethered swimming microrobots. The amalgamation compensates for their inherent constraints, ensuring a robust and highly efficient delivery of microrobots under complex physiological conditions over extensive distances. Concurrently, a hierarchical vascular network encompassing engineered arteries/veins and capillary networks was constructed by integrating vasculogenesis and endothelial cell (EC) lining strategies, thereby providing an in vivo-like testing platform for microrobots. Experimental evidence demonstrates that the flexible microrobotic guidewire can be precisely directed to any entrance of the second-tier branches, with its inner lumen providing an "express lane" for rapid passage of microrobots through complex fluidic environments without direct contact. After release, dynamically assembled swarms could effectively locomote on the micro-topography of the EC-lined channel surface without becoming trapped and congregate within specified regions inside capillary lumens when guided collectively by a biologically safe magnetic field. Additionally, the superparamagnetic capabilities of microrobotic swarms ensure their dissolution into monodispersed entities upon withdrawal of the magnetic field, mitigating the risk of intravascular thrombosis. The hierarchical vascularized organ-on-a-chip platform establishes a comprehensive testing platform that integrates imaging, control, and a functional 3D microvascular environment, thereby enhancing its suitability for microrobotic applications encompassing targeted drug delivery, thrombus ablation, sensing and diagnosis, etc.