Magnetically actuated soft robots may improve the treatment of disseminated intravascular coagulation. Significant progress has been made in the development of soft robotic systems that steer catheters. A more challenging task, however, is the development of systems that steer sub-millimeter-diameter guidewires during intravascular treatments; a novel microrobotic approach is required for steering. In this article, we develop a novel, magnetically actuated, soft microrobotic system, increasing the steerability of a conventional guidewire. The soft microrobot is attached to the tip of the guidewire, and it is magnetically steered by changing the direction and intensity of an external magnetic field. The microrobot is fabricated via replica molding and features a soft body made of polydimethylsiloxane, two permanent magnets, and a microspring. We developed a mathematical model mapping deformation of the soft microrobot using a feed-forward approach toward steering. Then, we used the model to steer a guidewire. The angulation of the microrobot can be controlled from 21.1° to 132.7° by using a magnetic field of an intensity of 15 mT. Steerability was confirmed by two-dimensional in vitro tracking. Finally, a guidewire with the soft microrobot was tested by using a three-dimensional (3D) phantom of the coronary artery to verify steerability in 3D space.

Biocompatibility and high responsiveness to magnetic fields are fundamental requisites to translate magnetic small‐scale robots into clinical applications. The magnetic element iron exhibits the highest saturation magnetization and magnetic susceptibility while exhibiting excellent biocompatibility characteristics. Here, a process to reliably fabricate iron microrobots by means of template‐assisted electrodeposition in 3D‐printed micromolds is presented. The 3D molds are fabricated using a modified two‐photon absorption configuration, which overcomes previous limitations such as the use of transparent substrates, low writing speeds, and limited depth of field. By optimizing the geometrical parameters of the 3D molds, metallic structures with complex features can be fabricated. Fe microrollers and microswimmers are realized that demonstrate motion at ≈20 body lengths per second, perform 3D motion in viscous environments, and overcome higher flow velocities than those of “conventional 3D printed helical microswimmers.” The cytotoxicity of these microrobots is assessed by culturing them with human colorectal cancer (HCT116) cells for four days, demonstrating their good biocompatibility characteristics. Finally, preliminary results regarding the degradation of iron structures in simulated gastric acid liquid are provided.

A needle‐type microrobot (MR) for targeted drug delivery is developed to stably deliver drugs to a target microtissue (MT) for a given period time without the need for an external force after affixing. The MRs are fabricatedby 3D laser lithography and nickel (Ni)/titanium oxide (TiO2) layers are coated by physical vapor deposition. The translational velocity of the MR is 714 µm s−1 at 20 mT and affixed to the target MT under the control of a rotating magnetic field. The manipulability of the MR is shown by using both manual and automatic controls. Finally, drug release from the paclitaxel‐loaded MR is characterized to determine the efficiency of targeted drug delivery. This study demonstrates the utility of the proposed needle‐type MR for targeted drug delivery to MT with various flow rates in vitro physiological fluidic environments.

Here, we develop a flexible microrobot enhancing the steerability of a conventional guidewire. To improve steerability, a microrobot is attached to the tip of the guidewire and guided using an external magnetic field generated by an electromagnetic coil system. The flexible microrobot is fabricated via replica-molding and features a body made of polydimethylsiloxane (PDMS) and a single permanent magnet. As the robot is made of a deformable material, it can be steered using a low-intensity external magnetic field; the robot can potentially be guided into the coronary artery. To study steering performance, we employed mathematical modeling and a finite element model (FEM), and performed experiments under various magnetic fields. We found that a mathematical model using the Euler-Bernoulli beam could not precisely calculate the deformation angles. The FEM more accurately estimated those angles. The deformation angle can be controlled from 0 to 80° at a magnetic field intensity of 15 mT. The trackability at angles of 45 and 80° of the guidewire-based microrobot was confirmed in vitro using a two-dimensional blood vessel phantom.

In article number 1901697 by Hongsoo Choi and co‐workers, a drug‐loaded micro‐robot can be attached to a target micro‐tissue by swimming in a corkscrew motion with magnetic torque under a rotating magnetic field. The needle‐type micro‐robot has the potential to improve targeted drug delivery to a micro‐tissue in vitro in physiological fluid environments.