Grain-Sized Soft Robots Controlled by Magnetic Fields Deliver Medical Drugs

Miniature robots hold significant potential to revolutionize targeted drug delivery by delivering high concentrations of medication directly to disease sites while minimizing complications. However, current miniature robots are limited in their capabilities; most can only transport a single type of drug, while those designed to carry multiple drugs lack the ability to alter their dispensing sequence or dosage. Additionally, the latter robots cannot transport more than three types of drugs, selectively dispense them, maintain mobility, or release drugs at multiple sites. A team of researchers has now created grain-sized soft robots that can be controlled via magnetic fields for targeted drug delivery, potentially enhancing therapeutic options in the future. This study, published in the journal Advanced Materials, represents the first instance of miniature robots capable of transporting up to four different drugs and releasing them in reprogrammable sequences and dosages.

In contrast to previous small-scale robots that could only carry up to three types of drugs and lacked programmable release capabilities, the new miniature robots developed by scientists at NTU’s Nanyang Technological University (Singapore) provide precision functions that could significantly enhance therapeutic outcomes while reducing side effects. The NTU team had earlier developed magnetically controlled miniature robots capable of intricate maneuvers, such as ‘swimming’ through tight spaces and grasping tiny objects. Building upon this earlier research, the team drew inspiration from the 1960s film ‘Fantastic Voyage,’ in which a crew is miniaturized to repair damage within a scientist's brain.

The grain-sized robots were constructed using smart magnetic composite materials (magnetic microparticles and polymers) that are safe for human use. Unlike existing miniature robots that cannot precisely control their orientation, the newly developed soft robots demonstrate high dexterity, allowing them to roll and crawl quickly to navigate obstacles. This dexterity is advantageous for traversing complex, unstructured environments within the human body. In laboratory experiments, the robots performed tasks in water simulating conditions within the human body. Initially placed on a surface divided into four sections, the robots successfully moved to each section at speeds ranging from 0.30 mm to 16.5 mm per second, releasing different drugs in each area, which confirmed their ability to carry multiple drugs and program their release in a controlled manner.

In another experiment, researchers assessed the robots’ drug delivery capabilities in more challenging environments using a thicker liquid. The results indicated that the robots could navigate through this environment and effectively release sufficient quantities of drugs over eight hours. Furthermore, after eight hours of continuous operation, the robots displayed minimal drug leakage. This capacity for controlled drug release without excessive leakage positions the soft robots as promising candidates for therapies that require precise delivery of multiple drugs at varying times and locations. The NTU research team aims to reduce the size of these robots even further so they can potentially be employed in groundbreaking treatments for conditions such as brain tumors, bladder cancer, and colorectal cancer. Before these tiny robots are utilized for such medical applications, the researchers plan to further assess their performance using organ-on-chip devices and animal models.

“What was a scenario in a sci-fi movie is now becoming closer to reality with our lab’s innovation,” said lead investigator, Assistant Professor Lum Guo Zhan from the School of Mechanical and Aerospace Engineering (MAE). “Traditional methods of drug delivery like oral administration and injections will seem comparatively inefficient when stacked up against sending a tiny robot through the body to deliver the drug exactly where it is needed.”