Aug.28, 2012

Researchers at the Vienna University of Technology have developed a new method to grow biological tissue or to create micro sensors by using a laser beam.

Researchers have had a breakthrough before: to print 3D objects with incredibly fine details using "two-photon lithography", such as a racing car with about 285 micrometers length.

With laser beams, molecules can be fixed at exactly the right position in a three dimensional material. When biological tissue is grown, this method can allow the positioning of chemical signals, telling living cells where to attach. The new technique also holds promise for sensor technology: A tiny three dimensional "lab on a chip" could be created, in which accurately positioned molecules react with substances from the environment.

Molecules in the Hydrogel – Locked into Position by the Laser

This new technique is called "3D-photografting". It works like regular 3D printing only on a much smaller scale. The scientists start with a so-called hydrogel – a material made of macromolecules, arranged in a loose meshwork. Between those molecules there are large pores so that other molecules or even cells can migrate.

Using a beam of laser light, scientists are able to introduce selected molecules into the hydrogel meshwork. At the positions where the focused laser beam is most intense, a photochemically labile bond is broken. That way, highly reactive intermediates are created which locally attach to the hydrogel very quickly. The precision depends on the laser's lens system, at the Vienna University of Technology a resolution of 4 µm could be obtained.

"Much like an artist, placing colors at certain points of the canvas, we can place molecules in the hydrogel – but in three dimensions and with high precision", says Dr. Aleksandr Ovsianikov.

(A laser shines into the hydrogel (yellow), attaching molecules to it at specific points in space (green). Credit: Vienna University of Technology)

(This is a 3-D pattern produced by photografting (180 µm wide). Fluorescent molecules are attached to the hydrogel, resulting in a microscopic 3-D pattern. Credit: Vienna University of Technology)

3D photografting can be used to artificially grow biological tissue. Like a climbing plant clinging to a rack, cells need some scaffold at which they attach. In a natural tissue, the extracellular matrix does the trick by using specific amino acid sequences to signal the cells, where they are supposed to grow.

Other possibility for 3D photografting is photovoltaics or sensor technology. In a very small space, molecules can be positioned which attach to specific chemical substances and allow their detection. A microscopic three-dimensional "lab on a chip" becomes possible.

The new research results made the cover of Advanced Functional Materials: The original publication can be accessed there.


Source: Sciencedaily


Posted in 3D Technology




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