A major challenge to 3D printing living tissues is that many 3D printing techniques are based on using heat or ultraviolet light, which can damage or kill living cells.
To address this challenge, researchers at the University of Twente (UT) in Enschede, Netherlands are taking a page from biochip technology that adapted microfluidics for a variety of biocompatible applications.
Originally used in development of inkjet print heads, microfluidics involves the physics needed to manipulate and study minute amounts of fluids. Biochips, or as they are sometimes called "lab-on-a-chip" systems, use microfluidics to manipulate micro fluids through tiny channels to integrate one or several laboratory functions.
Biochips are used for screening tests and DNA microarrays to measure genetic activity of multiple genes simultaneously. Biochips manipulate micro fluids through micro channels at rates in the microliter per minute. To put that into perspective at that rate filling a volume of one cubic centimeter would take 17 hours.
According to UT researchers Tom Kamperman of the Developmental BioEngineering group of Prof Marcel Karperien, and Claas Willem Visser of the Physics of Fluids group of Prof Detlef Lohse’s group, using microfluidics for additive manufacturing could speed up the output of micro fluids by factors of 100 to 1000.
In a study published in the journal Science Advances Visser, Kamperman, et al demonstrated an in-air microfluidics (IAMF) technique that increased the per-channel throughput by up to 100 times that of chip-based droplet microfluidics. The technique uses two liquid jet nozzles aimed at each other in such a way that in-air impact encapsulates two reactive liquids that solidify in a compound.
The pair write that their approach maintains the in-line control of chip-based microfluidics but relies on jet ejection and mid-air encapsulation. This allows for production of a wide range of droplets and particles at flow rates 10 times greater than can be produced with chip-based microfluidics. When combining reactive, solidifying microjets, IAMF also enables on-the-fly production and can directly deposit microparticles into 3D multiscale modular (bio)materials.
Their project demonstrated that in-air formed particles can be used as living cell compatible building blocks for the printing of larger 3D biomaterials with a variety of architectures. The particle shape can be controlled by manipulating the surface tension of the liquids and altering the velocity ratio between the nozzles.
The scientists conclude that through direct deposit of in-air-formed particles onto a substrate, in-air microfluidics enable printing 3D modular biomaterials in a single step. The implication for tissue engineering is that such a process could be used for high throughput additive manufacturing of cell-containing materials without harming the living cells.
Source: University of Twente news and Science Advances 31 Jan 2018: Vol. 4, no. 1, eaao1175
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