A small card turns into a robot when it is heated and can move without being plugged in. New research from Harvard and Caltech is published in Nature

Latest update time：2019-08-28

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A small white translucent card was placed on a hot surface at 200 degrees Celsius and it rolled up immediately.

Not only can it roll up, but it can also run forward step by step. Every time a new surface comes into contact with a hot surface, it can be pushed to turn to the next surface. The researchers named it Rollbot .

Change the shape, throw it into hot water, and fold it up quickly.

Seen from the side, this fold looks just like a frog.

If you look closely, you will find that the different "joints" of the small card do not bend synchronously. Some move first and some move later, folding into the shape of a paper clip.

If it is taken out of the hot water and the temperature drops, it can unfold and flatten itself again.

In fact, this is a soft robot developed by Harvard University and Caltech. Yes, it is not plugged in, but it is still a robot. As long as it is heated, it can bend, transform and move.

Because it can flexibly "transform" in different environments, and the material structure is adjustable to set the bending environment and angle, this soft robot can lay the foundation for passive control in the medical and industrial fields in the future.

When you get hot, it bends

Why does a good robot become bent?

This is due to a special hinge structure.

These hinge structures are 3D printed and made of LCE (liquid crystal elastomer).

LCE will bend at a certain temperature and straighten below this temperature. There is a transition temperature between the two states .

The researchers used two LCE materials. Due to the differences in skeleton flexibility and cross-linking chemical properties, the transition temperatures of the two LCE materials were different, one at 24 degrees Celsius and the other at 96 degrees Celsius.

The chemical formulas of the two materials are different. The blue box in the figure below is an LCE material with a transition temperature of 24 degrees Celsius, and the orange box is an LCE material with a transition temperature of 96 degrees Celsius.

After that, 3D printing is required. Due to the different horizontal and vertical arrangements of the double-layer printing, the printed hinge structure will bend to both sides according to the Mountain shape and Valley shape when the temperature changes.

In this way, the folding direction of the finished product can be controlled, with some edges folded outwards and some edges folded inwards, and the transformation is fully automatic without the need for human intervention.

In addition, the folding angle can also be controlled. Although it can reach 180 degrees of folding, the specific angle is closely related to the material and size of the hinge.

Bend in any way you like

Therefore, by using this hinge, you can preset in advance which direction the small card should bend, at what temperature, and at what angle. In this way, you can design a suitable soft robot based on the specific application scenario and environment.

For example, this soft robot structure has a total of 50 coaches, each of which is 6 mm wide and 0.5 mm thick and can be folded to 180 degrees.

At room temperature, it looks like this, with both connected cubes unfolded:

When heated to 95 degrees, the block above flattens itself:

Heated to 155 degrees, the following blocks also flattened:

But if returned to room temperature, both cubes will unfold again.

Produced by Harvard & Caltech

This study had two co-first authors.

One is Arda Kotikian, who majored in chemistry and mathematics in college and is currently a graduate student at the Harvard John A. Paulson School of Engineering and Applied Mathematics, where she has been researching the development of soft robots using LCE materials.

Another is Connor McMahan, a PhD candidate in mechanical and civil engineering at Caltech who has been studying predictive shape-changing structures. He is also a NASA Fellow.