Zwitterionic 3D- Printed Non- Immunogenic Stealth Microrobots

Microrobots offer transformative solutions for non- invasive medical interventions due to their small size and untethered operation inside the human body. However, they must face the immune system as a natural protection mechanism against foreign threats. Here, non- immunogenic stealth zwitterionic microrobots that avoid recognition from immune cells are introduced. Fully zwitterionic photoresists are developed for two- photon polymerization 3D microprinting of hydrogel microrobots with ample functionalization: tunable mechanical properties, anti- biofouling and non- immunogenic properties, functionalization for magnetic actuation, encapsulation of biomolecules, and surface functionalization for drug delivery. Stealth microrobots avoid detection by macrophage cells of the innate immune system after exhaustive inspection (>90 hours), which has not been achieved in any microrobotic platform to date. These versatile zwitterionic materials eliminate a major roadblock in the development of biocompatible microrobots, and will serve as a toolbox of non- immunogenic materials for medical microrobot and other device technologies for bioengineering and biomedical applications.Zwitterionic stealth microrobots avoid detection and capture by immune cells. Zwitterionic microrobots with anti- biofouling, stealth, and non- immunogenic properties are 3D- printed via two- photon- polymerization, and are functionalized for magnetic actuation, encapsulation of biomolecules, and drug delivery. The microrobots remain undetected by macrophages and other immune cells for at least 90 hours, overcoming a major roadblock in medical microrobotics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163416/3/adma202003013-sup-0001-SuppMat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163416/2/adma202003013.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163416/1/adma202003013_am.pd

Electrochemistry: A basic and powerful tool for micro- and nanomotor fabrication and characterization

Electrochemistry, although an ancient field of knowledge, has become of paramount importance in the synthesis of materials at the nanoscale, with great interest not only for fundamental research but also for practical applications. One of the promising fields in which electrochemistry meets nanoscience and nanotechnology is micro/nanoscale motors. Micro/nano motors, which are devices able to perform complex tasks at the nanoscale, are commonly multifunctional nanostructures of different materials - metals, polymers, oxides- and shapes -spheres, wires, helices- with the ability to be propelled in fluids. Here, we first introduce the topic of micro/nanomotors and make a concise review of the field up to day. We have analyzed the field from different points of view (e.g. materials science and nanotechnology, physics, chemistry, engineering, biology or environmental science) to have a broader view of how the different disciplines have contributed to such exciting and impactful topic. After that, we focus our attention on describing what electrochemical technology is and how it can be successfully used to fabricate and characterize micro/nanostructures composed of different materials and showing complex shapes. Finally, we will review the micro and nanomotors fabricated using electrochemical techniques with applications in biomedicine and environmental remediation, the two main applications investigated so far in this field. Thus, different strategies have thus been shown capable of producing core-shell nanomaterials combining the properties of different materials, multisegmented nanostructures made of, for example, alternating metal and polymer segments to confer them with flexibility or helicoidal systems to favor propulsion. Moreover, further functionalization and interaction with other materials to form hybrid and more complex objects is also shown

The mismatch between experimental and computational fluid dynamics analyses for magnetic surface microrollers

Abstract Magnetically actuated Janus surface microrollers are promising microrobotic platform with numerous potential biomedical engineering applications. While the locomotion models based on a "rotating sphere on a nearby wall" can be adapted to surface microrollers, real-world dynamics may differ from the proposed theories/simulations. In this study, we examine the locomotion efficiency of surface microrollers with diameters of 5, 10, 25, and 50 µm and demonstrate that computational fluid dynamics simulations cannot accurately capture locomotion characteristics for different sizes of microrollers. Specifically, we observe a significant mismatch between lift forces predicted by simulations and opposite balancing forces, particularly for smaller microrollers. We propose the existence of an unaccounted force component in the direction of lift, which is not included in the computational fluid dynamics simulations. Overall, our findings provide a deeper understanding of the physical mechanisms underlying surface microroller locomotion and have important implications for future applications in biomedical engineering

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.ISSN:0935-9648ISSN:1521-409

Shape anisotropy-governed locomotion of surface microrollers on vessel-like microtopographies against physiological flows

Surface microrollers are promising microrobotic systems for controlled navigation in the circulatory system thanks to their fast speeds and decreased flow velocities at the vessel walls. While surface propulsion on the vessel walls helps minimize the effect of strong fluidic forces, three-dimensional (3D) surface microtopography, comparable to the size scale of a microrobot, due to cellular morphology and organization emerges as a major challenge. Here, we show that microroller shape anisotropy determines the surface locomotion capability of microrollers on vessel-like 3D surface microtopographies against physiological flow conditions. The isotropic (single, 8.5 μm diameter spherical particle) and anisotropic (doublet, two 4 μm diameter spherical particle chain) magnetic microrollers generated similar translational velocities on flat surfaces, whereas the isotropic microrollers failed to translate on most of the 3D-printed vessel-like microtopographies. The computational fluid dynamics analyses revealed larger flow fields generated around isotropic microrollers causing larger resistive forces near the microtopographies, in comparison to anisotropic microrollers, and impairing their translation. The superior surface-rolling capability of the anisotropic doublet microrollers on microtopographical surfaces against the fluid flow was further validated in a vessel-on-a-chip system mimicking microvasculature. The findings reported here establish the design principles of surface microrollers for robust locomotion on vessel walls against physiological flows.ISSN:0027-8424ISSN:1091-649

3D Microprinting of Iron Platinum Nanoparticle‐Based Magnetic Mobile Microrobots

Wireless magnetic microrobots are envisioned to revolutionize minimally invasive medicine. While many promising medical magnetic microrobots are proposed, the ones using hard magnetic materials are not mostly biocompatible, and the ones using biocompatible soft magnetic nanoparticles are magnetically very weak and, therefore, difficult to actuate. Thus, biocompatible hard magnetic micro/nanomaterials are essential toward easy‐to‐actuate and clinically viable 3D medical microrobots. To fill such crucial gap, this study proposes ferromagnetic and biocompatible iron platinum (FePt) nanoparticle‐based 3D microprinting of microrobots using the two‐photon polymerization technique. A modified one‐pot synthesis method is presented for producing FePt nanoparticles in large volumes and 3D printing of helical microswimmers made from biocompatible trimethylolpropane ethoxylate triacrylate (PETA) polymer with embedded FePt nanoparticles. The 30 μm long helical magnetic microswimmers are able to swim at speeds of over five body lengths per second at 200 Hz, making them the fastest helical swimmer in the tens of micrometer length scale at the corresponding low‐magnitude actuation fields of 5–10 mT. It is also experimentally in vitro verified that the synthesized FePt nanoparticles are biocompatible. Thus, such 3D‐printed microrobots are biocompatible and easy to actuate toward creating clinically viable future medical microrobots.ISSN:2640-456