Shape-shifting, scuttling, microbots

By | Science & Technology
This tiny transformer begins as a flat square that weighs just a third of a gram and looks like a piece of foil - it can walk, swim, and even dissolve itself. Credit@Evan Ackerman/IEEE Spectrum

Researchers from MIT and Technische Universität München unfurled an untethered miniature origami robot that self-folds, walks, swims, and degrades at ICRA 2015 in Seattle last week. The team on all of those promises as the clever microbot demonstrated that from a simple flat sheet with a magnet, in a few seconds it may fold itself up, zip around on land or water and when it has finished its duties, use an embedded tank of acetone to dissolve itself. It is the first time a robot has been capable of demonstrating a life cycle like this and researchers are aiming for it to take place inside the human body. “This is the first time that a robot has been able to demonstrate a complete life cycle like this,” wrote IEEE Spectrum’s Evan Ackerman. “And eventually, it’ll be doing it inside your body.”

The unfolded robot is made of a magnet and PVC sandwiched between layers of polystyrene or paper. It weighs a mere 0.31 grams and is only 1.7 centimetres long. When activated by a small heat source, the PVC contracts and folds along where the structural layers have been cut in under a minute.

The robot’s movement is ‘powered’ in two parts: (1) a cubic neodymium magnet that the robot folds itself around and (2) a set of four electromagnetic coils beneath the surface to generate a magnetic field to drive it. The magnetic field continuously turns off and on at 15 Hz causing the magnet that the robot is attached to to oscillate back and fourth, which causes the robot to oscillate as well. In doing so, the front and back legs of the microbot alternately touch the ground. Combined with the asymmetrical design and intentionally off-centre balance, the robot is then able to walk, and even swim, forward at a rate of 3 cm/second.

A folding robot may afford many advantages. The ability to fold allows it to float as well as perform tasks like ‘digging’ or moving objects more effectively. Furthermore, the folding process might also be made multi-stage with different intensities of heating potentially folding the robot into different configurations with bespoke functions for each configuration.

The microbot is controlled by a magnetic field and can even carry heavy loads, relative to its own size and weight. The diagram shows how the sheet of PVC is folded. Credit@Shuhei Miyashita

The microbot is controlled by a magnetic field and can even carry heavy loads, relative to its own size and weight. The diagram shows how the sheet of PVC is folded. Credit@Shuhei Miyashita

Eventually, the miniature robot may self-direct its degradation by driving into a tank of acetone where it completely dissolve except for one small magnet. Researchers are also aiming for it to be dissolvable in water so that the robots may melt away entirely within the human body (although that appears to be more challenging).

“The dissolving process of the water-degradable model was tested under the assumption that future advancements [aim to] make the model biodegradable,” the paper reads. “To construct a biodegradable model for clinical use, the contraction layer (PVC film) and the adhesive layer need to be replaced with biodegradable counterparts.”

The researchers also aim to include self-folding sensors to the body of the robot in the “near future”. This may strengthen their level of autonomy and increase potential to perform delicate medical tasks within the body.

The robot is able to move using an external magnetic field, which is projected from four coils in a box beneath it (pictured), without the need for a battery in the robot itself. The machine may be instructed to self-dissolve by entering a tank of acetone (also illustrated), which melts away everything but the magnet. Credit@Shuhei Miyashita

The robot is able to move using an external magnetic field, which is projected from four coils in a box beneath it (pictured), without the need for a battery in the robot itself. The machine may be instructed to self-dissolve by entering a tank of acetone (also illustrated), which melts away everything but the magnet. Credit@Shuhei Miyashita

The team says that they are working to make the microbot even more self-sufficient and possibly completely autonomous. “Such autonomous ‘4D-printed’ robots [might] be used at unreachable sites, including those encountered in both in vivo and bionic biological treatment,” the paper reads. Eventually, researchers aim to use the bots in medical treatments by injecting them into the bloodstream to carry out medical procedures before melting away without a trace.

Which films featuring miniature robots treating the human body might now be considered a possibility, given the new research?

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