www.3ders.org

Aug 16, 2018

In 3D printing by direct laser writing, a computer-controlled, highly focused laser beam acts as a pen and produces a desired structure in a photoresist (a light sensitive material). This allows producing 3D structures with details in the sub-micrometer range.

Three-dimensional microstructures made of various cleavable photoresists. The scanning electron microscopies show the selective degradation of the structures (scaling 20 µm). (© Nature Communications) 

Martin Wegener, Eva Blasco, and Christopher Barner-Kowollik, Karlsruhe Institute of Technology (KIT), Germany, and colleagues have developed 3D inks based on labile silane crosslinkers that can be selectively erased. This allows specific degradation and reassembly of highly precise structures on the micrometer and nanometer scales under mild conditions.

"The high resolution is very attractive for applications requiring very precise filigree structures, such as in biomedicine, microfluidics, microelectronics or for optical metamaterials," says Professor Christopher Barner-Kowollik, head of the Macromolecular Architectures Group of KIT's Institute for Chemical Technology and Polymer Chemistry (ITCP) and of the Soft Matter Materials Group of Queensland University of Technology (QUT) in Brisbane, Australia.

Over a year ago, the working groups of Professor Martin Wegener at the Institute of Applied Physics (APH) and the Institute of Nanotechnology (INT) of KIT and of Professor Christopher Barner-Kowollik developed an erasable 3D printing ink. Thanks to reversible binding, small structures of up to 100 nanometres (with one nanometer corresponding to one millionth of a meter) can be erased and rewritten repeatedly.

Now, the scientists from Karlsruhe and Brisbane have largely refined their development. As reported in the journal Nature Communications, they have developed several inks, in different colors, so to speak, that can be erased independently of each other. This enables selective and sequential degradation and reassembly of the laser-written microstructures.

In case of highly complex constructions, temporary supports can be produced and removed again later on. It may also be possible to add or remove parts to or from three-dimensional scaffolds for cell growth, the objective being to observe how the cells react to such changes. Moreover, the specifically erasable 3D inks allow for the exchange of damaged or worn parts in complex structures.

When producing the cleavable photoresists, the researchers were inspired by degradable biomaterials. The photoresists are based on silane compounds that can be cleaved easily. Silanes are silicon-hydrogen compounds. The scientists used specific atom substitution for preparing the photoresists. In this way, microstructures can be degraded specifically under mild conditions without structures with other material properties being damaged.

This is the major advantage over formerly used erasable 3D inks. New photoresists also contain the monomer pentaerythritol triacrylate that significantly enhances writing without affecting cleavability.

 

 

Posted in 3D Printing Technology

 

 

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