High‐Performance Magnetic FePt (L1₀) Surface Microrollers Towards Medical Imaging‐Guided Endovascular Delivery Applications

Abstract

Controlled microrobotic navigation in the vascular system can revolutionize minimally invasive medical applications, such as targeted drug and gene delivery. Magnetically controlled surface microrollers have emerged as a promising microrobotic platform for controlled navigation in the circulatory system. Locomotion of micrororollers in strong flow velocities is a highly challenging task, which requires magnetic materials having strong magnetic actuation properties while being biocompatible. The L10‐FePt magnetic coating can achieve such requirements. Therefore, such coating has been integrated into 8 µm‐diameter surface microrollers and investigated the medical potential of the system from magnetic locomotion performance, biocompatibility, and medical imaging perspectives. The FePt coating significantly advanced the magnetic performance and biocompatibility of the microrollers compared to a previously used magnetic material, nickel. The FePt coating also allowed multimodal imaging of microrollers in magnetic resonance and photoacoustic imaging in ex vivo settings without additional contrast agents. Finally, FePt‐coated microrollers showed upstream locomotion ability against 4.5 cm s−1 average flow velocity with real‐time photoacoustic imaging, demonstrating the navigation control potential of microrollers in the circulatory system for future in vivo applications. Overall, L10‐FePt is conceived as the key material for image‐guided propulsion in the vascular system to perform future targeted medical interventions.

Real-time 3D optoacoustic tracking of cell-sized magnetic microrobots circulating in the mouse brain vasculature

“…Another study showed the visualization of 100-μm-long helical microrobots inside phantoms and ex vivo chicken breasts ( 40 ). OAT was used to visualize FePt-coated spherical microrobots that were directly injected into the muscular tissue of a dead mouse ( 41 ). The visualized particle agglomeration consisted of around 30,000 individual microrobots while the image acquisition took 45 min due to the low optical absorption contrast exhibited by the robots that were not optimized for sensitive OAT detection.…”

“…Even in the case of soft-bodied deformable microrobots, their size should not exceed 10 to 20 μm to allow for safe travel through capillaries ( 22 ). Moreover, the insufficient optical absorption contrast of microrobot materials used in previous studies has restricted the monitoring ability to large-sized robots or otherwise large particle agglomerates under ex vivo conditions ( 41 ). Last, no simultaneous actuation and tracking under OAT have so far been demonstrated.…”

Universal optothermal micro/nanoscale rotors

“…It becomes more challenging to achieve light-driven out-ofplane rotation (i.e., rotation of an object around an axis parallel to the substrate) (24,25). By enabling three-dimensional (3D) interrogation of objects such as biological particles, out-of-plane rotation techniques would improve rolling cell adhesion measurements (26,27), single-cell engineering (28), organism identification (29), and microsurgery (30)(31)(32)(33). Recently, light-driven out-of-plane rotation has only been realized using multiple-beam optical tweezers (10,34) or combining light with a microfluidic field (35) or an external electric field (36).…”

Ultrasound‐Controlled Swarmbots Under Physiological Flow Conditions

“…[33] Bozuyuk et al demonstrated upstream navigation of magnetic micro rollers on various 3D surface micro topographies. [34,35] Finally, Wang et al used magnetic swarms that could assemble in stagnant Navigation of microrobots in living vasculatures is essential in realizing targeted drug delivery and advancing non-invasive surgeries. Acousticallycontrolled "swarmbots" are developed based on the self-assembly of clinically-approved microbubbles (MBs).…”