3D printing of flexible porous silicone

A METHOD of 3D-printing porous, biocompatible silicone directly inside aqueous medium has been described by researchers, which could lead to biomedical or soft-robotics products.

Thermoplastics can be easily 3D-printed, as their extruded hot melt material solidifies rapidly during the process, allowing the addition of the next layer. Liquid polymer precursors such as polydimethylsiloxane (PDMS), however, are more challenging as they take longer to cure. PDMS, often known as silicone, is of particular interest for the additive technique as it is a widely used elastomeric polymer with unique physical properties and biocompatibility.

A new technique capable of directly 3D-printing PDMS has now been described by an international team of researchers. Printing was demonstrated in both dry and wet environments, with the group suggesting that it has the potential to be used to print on to live tissue for example bandages.

Their method used a capillary suspension ink containing PDMS in the form of both precured microbeads and uncured liquid precursor, dispersed in water as continuous medium. The liquid silicone rubber was used to form bridges between the PDMS microbeads, resulting in a printable granular paste. As the ink was ejected onto already deposited underlayers at a typical speed of 300mm/sec, any new layers did not affect the 3D shape of the existing structures. The printed structure was then cured at 85 °C.

Orlin Velev, professor of chemical and biomolecular engineering at North Carolina State University in the US, said: “Our method uses an extremely simple extrudable material that can be placed in a 3D printer to directly prototype porous, flexible structures – even under water.

“And it is all accomplished with a multiphasic system of just two materials – no special chemistry or expensive machinery is necessary. The 'trick' is that both the beads and the liquid that binds them are silicone, and thus make a very cohesive, stretchable and bendable material after shaping and curing.'

The authors of the paper, published in Advanced Materials, believe that the resulting elastic structures could have a broad range of uses where soft materials or microarchitectures are required. This could include soft-robotics or biomedical applications such as the creation of ultraflexible meshes to encapsulate a droplet of medicine, or soft bandages that can be applied or directly printed onto a portion of the human body.

Advanced Materials: http://doi.org/b8b9