Enter the morphing age with 4-D printing

"Intelligent" clothes that change colour, furniture which assembles itself and surgical instruments that can morph to fit different hands may sound far-fetched.

But research is now being carried out in Singapore that could turn these ideas into reality.

The Singapore University of Technology and Design (SUTD) is looking into 4-D printing, taking 3-D printing one step further by producing items that can be programmed to change their shape and properties.

In 3-D printing, advanced printers are used to build three-dimensional objects from the bottom up through layers of printing.

4-D printing may use the same machines to make materials that can be programmed to change over time.

The SUTD scientists created a way to make flat sheets, using a combination of materials, which fold themselves into a box or the shape of an aeroplane when heated. These could be the precursor to furniture which puts itself together.

The field of 4-D printing has gained traction globally in recent years because of its wide range of applications.

The United States Army Research Office recently funded work in this area in the hope of creating camouflage- changing uniforms.

The SUTD associate provost of research Martin Dunn said its four-strong team received funding from the Ministry of Education and US Air Force Office of Scientific Research earlier this year. He declined to comment on how much it was awarded.

The US office wants the team to work on the research's aerospace potential. The engineers' research includes how to create a spacecraft support structure that can morph into an antenna and back again to save space on board.

They will also look into creating new "shape-memory" composite materials that can "store" multiple shapes, and techniques to print them.

A simple version might consist of a composite material made of two plastics with different melting points - which could hold one shape at room temperature. When heated, one plastic relaxes, changing the material's shape. Heated further, the other plastic softens as well, allowing the material to take on a third shape.

The SUTD scientists are working on advanced composites that can revert back to the previous shapes.

These shape-memory materials can be printed as fibres in composites. "Multiple complex shapes can be achieved depending on how the fibres are embedded, such as their orientation, volume and location," said Prof Dunn. The researchers are also experimenting with different triggers for the transformations. These could include heat, electrical current, light and water thresholds.

The team published a paper on self-assembling structures in the science journal, Applied Physics Letters, last month.

zengkun@sph.com.sg

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