About a few years ago, if you would have presented to someone an idea that human tissues could be 3D Printed, they would have had you tested for lunacy. But fast forward to this day, and the same lunatic could now be hailed as a visionary. Today, we may have just come closer than ever in an attempt for 3D printing human tissue.
Thanks to the team from University of Twente, Netherlands for developing a novel and an engineering technique of 3D Printing human tissue. Their groundbreaking research was published in the journal of Science Advances. The following are the excerpts and understandings from their research.
Microfluidics deals with manipulating tiny drops of fluid with sizes as small as a micrometer (µm).  The diameter of human hair on an average is almost 75µm. So you can imagine the scale at which we are dealing here. Mostly chips with fine apertures for fluidic channels are used. These chips offer a broad range of possibilities, but the speeds at which these droplets leave the chip is quite slow for clinical applications — in the range of microliter per minute. This implies that filling a volume of a cubic centimeter would take about 16-18 hours. But the IAMF approach that the team from Twente developed, does this within a couple of minutes!
Courtesy: Claas Willem Visser et. al research paper titled “In-air microfluidics enables rapid fabrication of emulsions, suspensions, and 3D modular (bio)materials” in Science Advances.

3D Printing human tissue with “In-air microfluidics”:

The team observed that, the usual 3D Printing processes using heat and UV lights were detrimental to living cells. This prompted them to develop their own technique called as In-air microfluidics (IAMF). IAMF is an ultra-precise technique to print a tissue containing human living cells at high speed. IAMF consists of two nozzles. Each nozzle jets out fluid. These jets collide in-air and flow to the substrate. Jet 1 comprises of Alginate and Jet 2 comprises of Calcium Chloride (CaCl2). As seen from the image below, the fluid from Jet 1 breaks into tiny droplets which are then collided with the fluid from jet 2. The solid Alginate creates a soft, sponge-like tubular structure. Upon deposition onto a substrate, these soft particles stick to the construct without entrapping air bubbles and provide sufficient structural support for 3D freeform structures.
Courtesy: Claas Willem Visser et. al research paper titled “In-air microfluidics enables rapid fabrication of emulsions, suspensions, and 3D modular (bio)materials” in Science Advances.

Watch the video here:

IAMF also enables 3D Printing of varied, functional materials in one single step by controlling the in-air collisions and solidification of fluid droplets and their subsequent deposition onto a substrate. This ability of IAMF by far  contrasts chip-based microfluidics. IAMF allows control on the shape of the droplets that are solidified, high throughput, and cytocompatibility in 3D Printing human tissue compatible materials. This is a never seen before combination that had remained elusive in 3D Printed Human Organs, but is now possible by having a varying control on the material properties at the nozzle and those at the substrate; by selecting different types of fluids that react with each other, the jet collision can result in formation of new materials. We can even control the composition and force of jets; fibers with diameters as low as 20μm can be manufactured. And then there is the advantage of speed.
In the future, doctors could use techniques like IAMF to 3D print cells for repairing damaged tissue using cultured cell material of the patient. And maybe, one day we may even be able to 3D print entire organs.