Muscling in on artificial actuators

Scientists in the US have developed artificial "micromuscles" capable of functions like gripping, walking and even swimming. The team, based at Harvard University, US, created a series of muscular thin films (MTFs) by growing heart muscle cells from rats onto flexible plastic strips. These centimetre-scale MTFs could eventually be used in engineered devices of all sizes. 

The team, led by Kit Parker and George Whitesides, used electrical impulses to make the muscle fibres contract, causing the MTFs to roll up and ’grip’ objects. After the initial contraction, the muscle relaxes and the flexible plastic helps the muscle fibres to return to their original position. This pattern of contraction and relaxation can be controlled, or paced, leading to more diverse functions - pumping, for example. Inspired by the movement of simple organisms, the team developed simple MTFs that could be remotely controlled to walk or swim (as shown in a series of videos - click the ’micromuscles in action’  link below). 

Professor Nenad Bursac, an expert on heart cells at Duke Biomedical Engineering, North Carolina, told Chemistry World: ’In general the technology is very easy, because the cells do the work for you. The cells are all lined up in one direction so if you cut it into the shape of a triangle, the top has less cells and the base has more. That means it will be pulling more in one direction and therefore move forward.’ 

MTFs have a number of advantages over other types of artificial muscles - there is no need for an external power supply or battery for example. The team has also shown that MTFs are as strong as normal heart muscle and also very efficient. 

However, there are some problems with implementing this technology. Bursac explains: ’This work is still at an early stage in development. Right now it is difficult to maintain a lined-up muscle cell architecture for more than a couple of weeks, so I cannot see much potential for any long-term applications at present.’ 

The team believes that this research will be more widely applied than just engineering uses. It is hoped that analyzing the movements of MTFs will provide greater understanding of the mechanics of the human heart. 

Lewis Brindley 

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