Robots are continuing to gain more attention as researchers find new ways to implement them. Whether it’s in high-speed precision manufacturing; or using microfluidic robots for precision surgery, or cancer-fighting bots made of algae.
Recently researchers from Hong Kong City University have engineered a tiny, millimetre-scaled soft robot that resembles a caterpillar. The robot is designed to crawl around in harsh environments, such as inside the human body delivering drugs or performing medical procedures.
The robot’s design
The robot has hundreds of 1mm long legs embedded with magnetic particles, allowing it to be guided to specific areas within the body using an electromagnet. The robot legs can move along slippery surfaces within the body which are lined in fluids like blood or mucus.
The robot’s size is intentionally designed to match the leg structures of multi-legged animals. Especially how these legs are in proportion to the body, as well as the proportional gap in between them. This biologically inspired design eliminates friction up to 40 times less compared to similar legless robots by significantly reducing the areas of surface contact.
The device is made from a silicon material called polydimethylsiloxane (PDMS). PDMS makes the robot repel water using a “modified magnetic particle-assisted moulding approach”. The silicon is mixed with hexane and magnetic particles and put into a mould. During the curing process, an external magnetic field is used to pull out and form the tiny legs.
A magnetic force is applied in different patterns in order to make the robot move in specific ways. For instance, a magnetic force can be applied in a “flap propulsion” pattern to force it to move forward in a flapping motion. While a magnetic force applied in an “inverted pendulum” pattern will cause it to ‘swing’ itself forward by alternating steps to one side, and then the other.
When a magnetic field is applied, both magnetic and pulling force will be generated. Therefore, causing the tapered feet to align with the direct ion of magnetic flux. The robot then moves forward displaying various postures, in response to the combined action of the magnetic forces.
Achieving the impossible
Interestingly, the robot’s design has given it multipurpose powers that help it to overcome seemingly impossible obstacles. For example, it’s able to bend itself up to a 90-degree angle in order to cross over an obstacle that’s ten times larger in size than its leg length. In addition, when the frequency of the applied electromagnetic field is increased, the robot can speed up its movements in response. The robot also has a much larger carrying capacity than its tiny size would suggest, carrying a weight up to 100 times heavier than itself.
Compared to similar millimetre-sized gadgets, the robot moves with greater degrees of freedom. However, it requires less energy to do so. In the future, plans have been made to work on creating the robot out of biodegradable materials, as well as testing different designs for the form and features.
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