Helical microrobots cork-screw their way through water under magnetic control
A new type of multifunctional soft microrobot that shows great promise for biomedical applications has been developed by Josep Puigmartí-Luis and coworkers. The multifunctional helical device can swim along pre-defined tracks under control of weak rotational magnetic fields, and target single cells for controlled delivery of payloads.
In biomedical applications, it is envisioned that wireless swimming microrobots will be able to perform highly targeted delivery of cargo—such as drugs—to sites in the human body that are otherwise hard or invasive to reach. Such precision delivery will be hugely beneficial in diseases such as cancer, where collateral damage caused by untargeted drugs yields a significant health burden to cancer patients and survivors. Progress towards this vision of precision medicine is fundamentally reliant on our ability to build devices on the micro- and nanoscale, a task that requires highly precise manipulation of materials.
The microrobots produced in this new work are helical in structure, which means that they can cork-screw their way through liquid as they rotate in an applied magnetic field. They are fabricated by 3D-printing helices (with a diameter of 10 micrometers, and length 50 micrometers), then coated with nickel and titanium to make them magnetic and biocompatible. To make the helical swimmers capable of carrying a small molecule cargo, they were further coated in molecular-organic-framework (MOF) crystals. These are highly porous so can be loaded with molecular cargo, and they can be triggered to release their payload upon changes in pH. The team demonstrated the utility of their ‘MOFBOTS’ by loading them with fluorescent dye molecules to mimic a drug molecule, and they performed targeted delivery of this payload to specific breast cancer cells in a petri dish. Finally, they demonstrated precise control of payload release using a valve-based microfluidic device which could precisely control the pH conditions of the MOFBOTs, demonstrating effective payload release in low pH conditions.
The MOFBOTs developed in this work demonstrate an effective new approach to the fabrication of integrated multifunctional microsystems, and that the work will open up new avenues in the development of soft microrobots for many applications.
Written by Philip Howes
Read the full paper here.