Selectively controlled magnetic microrobots with opposing helices

Abstract

Magnetic microrobots that swim through liquid media are of interest for minimally invasive medical procedures, bioengineering, and manufacturing. Many of the envisaged applications, such as micromanipulation and targeted cargo delivery, necessitate the use and adequate control of multiple microrobots, which will increase the velocity, robustness, and efficacy of a procedure. While various methods involving heterogeneous geometries, magnetic properties, and surface chemistries have been proposed to enhance independent control, the main challenge has been that the motion between all microswimmers remains coupled through the global control signal of the magnetic field. Katsamba and Lauga [Phys. Rev. Appl. 5, 064019 (2016)] proposed transchiral microrobots, a theoretical design with magnetized spirals of opposite handedness. The competition between the spirals can be tuned to give an intrinsic nonlinearity that each device can function only within a given band of frequencies. This allows individual microrobots to be selectively controlled by varying the frequency of the rotating magnetic field. Here, we present the experimental realization and characterization of transchiral micromotors composed of independently driven magnetic helices. We show a swimming micromotor that yields negligible net motion until a critical frequency is reached and a micromotor that changes its translation direction as a function of the frequency of the rotating magnetic field. This work demonstrates a crucial step toward completely decoupled and addressable swimming magnetic microrobots.

Magnetically Driven Micro and Nanorobots

“… 226 In addition to the above-mentioned helical MagRobots, many other helical architectures have been created. 145 , 243 , 250 − 256 …”

“…By modifying their surface with polydopamine via dopamine self-polymerization (Figure G), Spirulina-based magnetic helical microswimmers exhibit an enhanced photoacoustic signal and photothermal effect . In addition to the above-mentioned helical MagRobots, many other helical architectures have been created. ,,− …”

Mobile Microrobots for In Vitro Biomedical Applications: A Survey

“…Moreover, the independent control of two helical microrobots was also reported by utilizing transchiral microrobots [42]. By using two helices with opposing handedness connected by a rod, a frequency dependent velocity profile can be realized and used to drive each microrobot independently [43]. On the other hand, bioinspired microrobots take the advantage of the efficient bacterialike motion in fluids with low Reynolds number [44], [45], [46].…”

Light‐Powered Microrobots: Challenges and Opportunities for Hard and Soft Responsive Microswimmers

“…The competition between the two spirals can be tuned by applying a magnetic field within a given band of frequencies for controlling the positive or negative advancement of the microrobots in microfluidic channels. [ 162 ] In the case of light‐powered microrobots, the same principle could be obtained using microrobots whose different parts are controlled by different wavelengths. By combining materials doped with dyes that have complementary absorption, color modulation can be introduced in the stimulus to control the movement asymmetry.…”