nano robots medical bots microrobots

Microrobots made of crystals able to propel themselves through water

Image credit: Dreamstime

Molecular-sized microrobots that can propel themselves through water have been developed by scientists at Hokkaido University in Japan.

The tiny devices, which mimic the abilities of some living organisms, were created with a form of a microcrystal that utilises self-continuous reciprocating motion for propulsion.

Historically, there have been two major challenges to achieving this kind of movement. The first is to make a molecular robot that can reciprocally deform; the second is converting this deformation into propulsion of the molecular robot.

The research team built on their previous study that had solved the first challenge: the creation of molecular robots that can reciprocally deform. However, tiny objects cannot typically convert their reciprocal motion into progressive motion.

The scientists managed to achieve self-propulsion of the molecular robot in an experimental system where motion was confined to two dimensions.

The microrobot was powered by blue light, which drove a series of reactions leading to the fin flipping and the propulsion.

Due to the nature of the reactions, the motion was not continuous, but rather occurred intermittently. In addition, the molecular robots exhibited one of three different styles of propulsion: a 'stroke' style, with the fin in front; a 'kick' style, with the fin behind, or a 'side-stroke' style, with the fin to one side.

The nature of mobility was affected by the area of the fin and its angle of elevation; individual crystals propelled themselves in different directions and styles.

The scientists then created a computational minimum model to understand the variables that affected the propulsion in a two-dimensional tank. They were able to determine that fin length, fin ratio and elevation angle were the key variables affecting the direction and the pace of propulsions.

“The result, which demonstrated that tiny flappers can swim assisted by the anisotropy caused by confined spaces, could spur research into molecular robots” said Yoshiyuki Kageyama, research team leader assistant professor.

“A similar mechanism may be in the movement of small aquatic organisms in specific conditions such as inside eggs,” he added.

The research could be a stepping stone towards the development of nanorobots that could be used in a medical setting. In 2017, another team developed magnetic ‘nanowires’ that can be navigated into hard-to-reach crevices inside the human body to diagnose and treat illnesses.

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