Lattices produced using fibers with nanometer-scale breadths have an extensive variety of potential applications. Be that as it may, their commercialization has been hampered by wasteful assembling systems.
To match the production rate and with increased power efficiency, MIT scientists have developed a new device for producing nanofibers’ meshes. It also reduces variation in the fibers’ diameters, an important consideration in most applications.
Scientists used a $3,500 commercial 3-D printer to build this device. It consists of an array of small nozzles through which a fluid containing particles of a polymer is pumped. Thus, it is known as a microfluidic device.
Luis Fernando Velásquez-García, a principal research scientist at MIT, said, “My personal opinion is that in the next few years, nobody will be doing microfluidics in the clean room. There’s no reason to do so. 3-D printing is a technology that can do it so much better with a better choice of materials, with the possibility to really make the structure that you would like to make. When you go to the clean room, many times you sacrifice the geometry you want to make. And the second problem is that it is incredibly expensive.”
Nanofibers’ applications often depend on fibers with regular diameters for better performance.
Velásquez-García said, “If you have a significant spread, what that really means is that only a few percent are really working. Example: You have a filter, and the filter has pores between 50 nanometers and 1 micron. That’s really a 1-micron filter.”
The earlier device was etched in silicon, which was externally fed. Its electric field drew a polymer solution up to the sides of the individual emitters. The fluid flow was regulated by rectangular columns etched into the sides of the emitters, but it was still erratic enough to yield fibers of irregular diameter.
In this new device, the emitters are internally fed and have holes bored through them. The hydraulic pressure pushes fluid into the bores until they’re filled, and the electric field draws the fluid out into tiny fibers.
Here, the taper is the essential thing that monitors the diameter of the nanofibers, and it would be virtually impossible to achieve with clean-room microfabrication techniques.
Velásquez-García said, “The device was engineered to demonstrate aligned nanofibers — that preserve their relative position as they’re collected by a rotating drum. Aligned nanofibers are particularly useful in some applications, such as tissue scaffolding. For applications with adequate unaligned fibers, the nozzles could be arranged in a grid, increasing output rate.”
Mark Allen, the Alfred Fitler Moore Professor at the University of Pennsylvania, noted, “A way to deterministically engineer the position and size of electrospun fibers allows you to start to think about being able to control mechanical properties of materials that are made from these fibers. It allows you to think about preferential cell growth along particular directions in the fibers — lots of good potential opportunities there.”
“I anticipate that somebody’s going to take this technology and use it in very creative ways. If you have the need for this type of deterministically engineered fiber network, I think it’s a very elegant way to achieve that goal.”