In-air microfluidics maintains the in-line control of chip-based microfluidics but relies on jet ejection and coalescence into air. Source: American Association for the Advancement of Science

A new technology from the University of Twente in the Netherlands enables 3D printing of structures with viable cells. In-air microfluidics is a chip-free platform that manipulates microscale liquid streams in the air and could be used to repair damaged tissue.

Chips with microfluidic channels, reactors and other components are widely used in lab-on-a-chip and other systems to control drops of fluid with sizes between a micrometer and a millimeter. The speed at which droplets leave the chip is typically in the microliter per minute range, which is not fast enough for clinical and industrial applications. While current systems would take about 17 hours to fill the volume of a cubic centimeter, the in-air microfluidic approach can do this in a matter of minutes.

Two jets of fluid are used to manipulate material in mid-air instead of in micro-channels. One jet directs droplets at the other; the droplets move 100 to 1,000 times faster than possible with a microchip. Different combinations of fluids can form solid, printable building blocks in a single step.

The process has been used to embed living cells inside printable material. The resulting bio building blocks are printed in a 3D structure resembling a fluid- and cell-filled sponge. The modular biomaterials have an internal structure similar to that of natural tissue. Many 3D printing techniques are based on using heat or UV light: both would damage living cells. The new microfluidic approach is therefore a promising technique in tissue engineering, in which damaged tissue is repaired by using the cultured cell material of the patient.

A spin-off, IamFluidics, is using the technology to develop functional particles and materials.

The research is published in the journal Science Advances.