Overview

Metin Sitti is a pioneer in wireless tiny medical robots, gecko-inspired adhesives, and bio-inspired miniature robots. His group, called the Physical Intelligence Department, strives to understand the principles of design, locomotion, control, perception, and learning of small-scale mobile robots.^[3] Sitti and his team aim to encode intelligence (e.g., sensing, actuation, control, memory, logic, computation, adaptation, learning and decision-making capabilities) into robots. They use smart stimuli-responsive materials, structures and mechanisms to encode intelligence into the physical body of a robot.^[4]

Research Focus

There is intelligence through brain power – neurons gathering and transmitting electrochemical signals that make a human, an animal or insect think. But there's another form of intelligence, and that is through the way the body is built. A gecko has feet that helps it stick to practically any surface, making his structure intelligent as it helps it survive in nature. Physical Intelligence means the hardware is smart, not just the software embedded in the brain.

Metin Sitti and his team's research ranges from small to milli- to microscale. Some robots are so tiny they have the size of a hair. Obviously, you can't add much hardware to such a small robot, so you have to be able to steer them around from outside, remotely. Magnetic, acoustic or light energy is the external force at play. Another way is using for instance live bacteria or algae to hook onto the robot – like a horse pulling a cart – to propel the robot forward. But how to control the bacteria which has a mind of its own? This is where biological engineering takes place where the bacteria is engineered in such a way that it is very fast in moving around, or senses specific things like a tumor.

The science in the Physical Intelligence Department is structured into three research thrusts. First, there is the Advanced Materials thrust where the researchers develop new bio-inspired, biological or synthetic materials for encoding physical intelligence into small-scale robots. As an example, his team designs, manufactures and applies gecko foot-hairs-inspired elastomer microfiber adhesives for controlled gripping, adhesion/friction, and liquid wetting of robot bodies or grippers and wearable soft sensors. Another example are self-healing and multifunctional protein materials, shape-programmable and multifunctional soft magnetic composites, stimuli-responsive liquid crystal elastomers and hydrogels, functional micro/nanomaterials, patient-derived biomaterials, and light-driven photocatalytic and liquid crystal materials for miniature soft robot actuation, propulsion, sensing, control, and physical adaptation.

Second, there is the Mobile Millirobots thrust where the robots are often down to 1 mm in size. Metin Sitti and his team look at insects, lizards, jellyfish, and many other small-scale organisms and try to understand the animal's locomotion principles and apply that knowledge to create robots at the small scale. There are also inventions such as a soft capsule robot, which looks much like a pill. One day, a patient could be able to swallow this capsule and it could take samples of a tumor inside the stomach. One of the main breakthroughs in this thrust area is a soft millirobot named Wormmate^[5] that is able to achieve seven different locomotions at the same time in multiple terrains (solid ground, water, water surface) inspired by soft-bodied small organisms. Sitti and his team are currently working on using this and other tiny robots to one day navigate through unprecedented and hard-to-reach regions inside the body under ultrasound or x-ray medical imaging for minimally invasive medical operations. This robotic breakthrough was published in Nature in 2018 and made the headlines all across the world.

Third, there is the Mobile Microrobots thrust, which Metin Sitti hopes will one day be a standard in healthcare or biotechnology. Microrobots, through their miniature size at a sub-millimeter scale (they are less than 1mm in all dimensions), could one day be able to access enclosed spaces such as microcapillaries inside a human body. They copuld travel through the body's fluids and directly interact with a tumor. Untethered mobile microrobots might enable many new applications, such as minimally invasive diagnosis and treatment inside the human body.

Soft milli- and microrobots such as those Metin Sitti and his team are developing hold huge potential and could one day have a radical impact on medicine. The scientists are working towards developing wireless tiny machines that in the near future will perhaps be able to access difficult-to-reach regions inside the body. As semi-implantable medical devices that are shape-programmable and built from biocompatible magnetic soft materials, these technologies would remain inside a patient's body for a long time, enabling minimally or non-invasive diagnostic and therapeutic interventions.

However, many challenges must still be overcome before these tiny robots can be applied in clinics. The scientists are still faced with many challenges: they must develop ways to move and control these tiny robots inside the body with high levels of precision, taking body fluid flows and organ movement into account. They must also ensure that patient safety is guaranteed, and that these robots can be in us for long periods of time, even in the face of potential immune or other reactions.