Scientists have created a small robot that can move, cut tissue, deliver drugs, grasp and store samples, and produce heat wirelessly.
The team from Nanyang Technological University, Singapore (NTU Singapore) has developed a seed-sized robot capable of navigating soft, uneven surfaces and performing five surgical functions wirelessly, paving the way for robots that make surgeries and medical treatments more precise.
The miniature robot, measuring just 4.4mm in length and controlled by weak magnetic fields, can perform any one of these functions at a time, including moving, cutting biological tissues, releasing drugs, gripping and storing tissue samples, or generating heat remotely.
It takes less than a second to switch between these functions.
Led by Associate Professor Lum Guo Zhan from NTU’s School of Mechanical and Aerospace Engineering (MAE), the work was recently published in the academic journal Advanced Materials.
Using magnetic coils in the laboratory to remotely control the robot, the team was able to make the robot deploy different tools and perform different functions, such as activating a tiny blade to cut through tissue or emitting heat to a targeted area, which could be relevant for approaches being studied that use heat for cancer treatment.
Assoc Prof Lum, who is a pioneer in miniature robots made from soft, flexible materials, said: ‘Most magnetic robots like this can perform only one or two functions. Our latest invention can now do five, and our long-term goal is for doctors to use these mini robots in the body, navigate them to a targeted location, and use them to perform treatments.’
To fit multiple functions into a robot only a few millimetres long, the NTU team developed a device for controlling movements that is activated by magnetic fields and can be reprogrammed in under a second.
The robot is made from soft magnetic materials, including PDMS and Ecoflex, which are silicone-based materials commonly used in soft robotics for their flexibility and ability to be shaped into small structures.
These materials are embedded with magnetic microparticles measuring five micrometres each, allowing different parts of the robot to respond to magnetic fields.
At the centre of the device is a magnetic module that can be magnetised, demagnetised and remagnetised in different directions.
Each magnetic orientation activates a different function of the robot, allowing the same mobile robot to perform five different functions, including cutting and grasping tissues.
The researchers also engineered different regions of the robot to ensure that only one part, but not the rest, responds to the same magnetic field.
This means that only one part of the robot responds to a magnetic field, changing shape to activate a tool or function. In contrast, other parts remain still and unchanged in their current forms, addressing a major limitation in miniature magnetic robots.
At small scales, magnetic fields often affect the entire device at once, causing it to behave like a single magnet, with all parts reacting to the field, thereby limiting how precisely it can move or activate different tools.
The NTU robot can roll, allowing it to spin about its long axis. This gives the robot finer control over its positioning – important for navigating narrow, soft, and irregular spaces, such as those inside the body.
It also has a solid but flexible body, making it sturdier and easier to retrieve after use.
The NTU team tested the robot’s surgical functions using biological tissue models, including chicken liver, as well as gelatin-based materials that simulate soft tissue.
In laboratory tests, the robot cut through biological tissues, dispensed particles simulating drug particles, gripped and stored tissue samples, and generated localised heat after being induced by magnetic fields.
To produce heat, the researchers exposed the robot to a high-frequency alternating magnetic field. This caused magnetic materials inside the device to generate heat remotely, in an approach relevant to magnetic hyperthermia methods being explored in cancer treatment.
The team also assessed the biocompatibility of the robot’s materials by exposing them to human skin cells in a laboratory setting.
More than 99% of the cells remained viable after exposure to the robot’s materials, comparable to the control group, indicating that the materials were largely non-toxic under the experimental conditions.
The team – including NTU’s MAE alumnae Dr Chelsea Shan Xian Ng and Ms Yu Xuan Yeoh, and current PhD student Nicholas Yong Wei Foo, who are co-authors of the research – is now exploring how future versions could be integrated with imaging technologies, sensing systems and clinically realistic artificial organ models that more accurately mimic the physical behaviour of human tissues.
Assoc Prof Lum is also working with surgeons to understand how mini-robotic systems could eventually fit into real-world clinical workflows.
