A team of engineers and scientists from Harvard's John A. Paulson School of Engineering and Applied Sciences (SEAS) have found another possible use for additive manufacturing . They have developed a simple 3D-printed device that they believe could be used to braid filaments as small as a micrometer in diameter. This could pave the way for manufacturing antennas to access ever higher frequency ranges for the next generation of phones and wireless devices.
Although cell phones have only been around since the early 70s and WIFI since the late 90s, the demands of our increasingly globalized and connected society have led to rapid advances in technology. WIFI, for example, is becoming more and more powerful and fast. South Korea, the top country for WIFI connectivity, tops the list with speeds of up to 28.6 Mbps.
Similarly, over the past twenty years we have seen mobile phones evolve rapidly from large, bulky phones that could only perform minimal tasks, although internet access and email have been present from the early 2000s, to sleek mini-computers that we now carry around in our pockets. However, if we want to advance even further, we must create new antennas to access new ranges, but current industrial manufacturing techniques will not work on fibers small enough to manufacture them, according to the Harvard team, because they do not cannot be braided together.
How is 3D printing used to improve WIFI?
For scientists and engineers, the solution seemed deceptively simple: use the surface tension of water to grasp and manipulate microscopic objects. To do this, the team turned to a machine that, in essence, is just a 3D-printed rectangle of plastic, the size of an old Nintendo game cartridge, and whose interior has been dug with intersecting canals.
These channels are both wide and narrow, reminiscent of a river that widens in some parts and narrows in others. Channel walls are also hydrophilic, meaning they attract water. The team also mentions that the rectangle could be made simply, with a desktop 3D printer, themselves seeming to use an SLA 3D printer, although they don't mention any particular brand.
Capillary action is the process by which a liquid flows through a narrow space without the aid of forces like gravity, and it is important when it comes to moving water. By submerging the device in water and placing a millimeter-sized plastic float in the channel, surface tension caused the wall to push the float back. In a narrow section, it pulled as far away from the walls as possible, while in a wider section, it was held in place, wedged between the repulsive forces of the walls and the float. By adding microscopic fibers to the floats, the researchers discovered that when the water level changed and the floats moved,
Maya Faaborg, associate at SEAS and co-author of the paper, explains: “ The 'eureka' moment came when we discovered that we could move objects by changing the cross-section of our channels. It was a moment of great joy when – on our first try – we crossed two fibers using only a piece of plastic, a water tank and a stage that goes up and down . The final step was to add a third float with a fiber and design channels to move the float in a braiding pattern. This method has been successfully used to braid micrometric size Kevlar fibers.
The research is still in its infancy, but it has huge implications for the future. The team plans to continue designing devices to handle many fibers at once to see if they can create high-frequency connectors that can, in turn, be used to make more powerful wireless devices (WIFI) and cell phones. Anyway, it was 3D printing that played a key role in creating the device responsible for this success thanks to its accessibility and ability to realize complex geometric structures.
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