Nov 16, 2015 | By Alec

With the quality of industrial 3D printing improving by leaps and bounds, it is now also increasingly being used on a microscopic scale – opening the way for a wide range of innovative breakthroughs. Case in point is the recent successes of a team of Chinese scientists led by Hepeng Zhang. With the help of 3D printing, they have tackled a typical obstacle in the microscopic world: motion. By embedding a series of bacteria in a microscopic 3D printed structure, they have created very small and versatile microscopic pumps.

Until now, scientists were able to move particles around with the help of macroscopic pumps that drive motion. These are, however, bulky, and don’t work particularly well when minimized. Fortunately, Hepeng Zhang and his team at the Shanghai Jiao Tong University have now developed a functional alternative that relies on the natural inhabitants of the microscopic world: motile bacteria. The great thing about these bacteria isn’t just that they’re already present in the medium in question, but that they’re also much more efficient motors for movement than alternative man-made motor systems.

Essentially, they are harnessing these bacteria in the same way a horse pulls a carriage: using the creature’s natural movement patterns for our own functions. These particular bacteria propel themselves forward with the help of their Flagella, a whip like structure that pushes a bacterium forward when in a fluid. Essentially, they push themselves forward such as we do in a swimming pool, but the Chinese team has found a way of embedding them in a single place, while their flagella continue to create flow patterns – which are strong enough to transport other materials.

‘We noticed some bacteria stuck on a glass coverslip could generate flow; this led us to the idea of using immobile bacteria as pumps,’ Zhang explains to Chemistry World. ‘We tried different ways to organise bacteria and found that microstructures are particularly suitable.’ But to create a structure capable of housing these bacteria was challenging, and they turned to 3D printing for a solution. 3D printed in liquid resin – which is harmless to bacteria – these structures consist of microscopic bricks with small cavities in them. Bacteria cannot swim backwards, so once they swim into a cavity, they’re trapped with their flagellum sticking out.

According to microorganism locomotion expert Saverio Spagnolie, from the University of Wisconsin, these cavities can best be seen as a series of tiny garages. ‘[This breakthrough] achieved much greater control of the flow field. An important inverse problem is then: given a desired flow field, how should you design the microbial parking lot?’ he speculates.

This initial proof of concept can be seen in the clip below, and Zhang and his team are already looking at enhancements that will offer micro specialists a wide range of tools to work with. In particular, the plan is to harness the power of bacteria with higher swimming speeds, to enable the flow to operate faster and affect large areas – opening the way for efficient delivery of particles, drugs and so on.



Posted in 3D Printing Application



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