3D printing allows for the efficient manufacture of complex geometries. A very promising method is direct laser writing in which a computer-controlled focused laser beam acts as a pen and produces the desired structure in a photoresist. In this way, three-dimensional structures with details in the sub-micrometer range can be produced for applications requiring very precise filigree structures such as biomedicine, microfluidics, microelectronics, or optical metamaterials.

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

A previously developed erasable ink for 3D printing has been refined, enabling the building blocks of the ink to be separated again. Several inks, in different colors, can be erased independently of each other. This enables selective and sequential degradation and reassembly of the laser-written microstructures. In the case of highly complex constructions, for instance, temporary supports can be produced and removed later. 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.

The cleavable photoresists are based on silane compounds that can be cleaved easily. Silanes are silicon-hydrogen compounds. Specific atom substitution was used in preparing the photoresists. In this way, microstructures can be degraded specifically under mild conditions without structures and without damaging other material properties. 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.

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Tech Briefs Magazine

This article first appeared in the January, 2019 issue of Tech Briefs Magazine.

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