Laser-based technique builds 3D micron-scaled structures

Researchers at the Vienna University of Technology have developed a method of building up three-dimensional, micron-scaled structures with tailored chemical or biological properties that could be the basis for complex sensors or even biological systems.

Known as 3D photografting, the system uses a focused laser as a kind of paint brush to set off chemical signals that direct compounds or cells to the chosen point within a block of material.

The researchers are from two teams that have previously worked on 3D printing — one from the university’s materials science department, led by Prof Jürgen Stampfl, and the other from a macromolecular chemistry research group led by Prof Robert Liska.

The technique, however, is not related to 3D printing, but is a development of a method previously used to modify the surface of a polymer.

The team started with a macomolecular hydrogel, a polymeric substance with a very low density whose structure is an open lattice with large pores. They seeded this structure with aromatic azide molecules, then irradiated the hydrogel with a laser focused to a point 4µm across. The light transforms the azide molecules into highly reactive groups onto which specific compounds will attach very quickly.

‘Much like an artist, placing colours at certain points on a canvas, we can place molecules in the hydrogel — but in three dimensions and with high precision,’ explained researcher Aleksandr Ovsianikov in a statement released by the university.

One use for this method is to utilise the hydrogel as a scaffold to support the growth of biological tissue. The laser can be used to position chemical groups inside the lattice that act as chemical signals for cells to attach at specific positions, where they can then start to grow into structures such as capillaries.

An alternative use might be to construct a three-dimensional ‘lab-on-a-chip’ system, using the laser to position compounds that bind to or react with a specific substance. Careful positioning could turn the hydrogel into a chemical sensor or analysis device, defining a path through the lattice that would guide the substance into a detector or reaction zone. These could be used for applications such as drug screening, according to the researchers.