Developing materials in which porosity can be controlled has been an aim for scientists due to their diverse uses in energy storage, sensors, tissue engineering, and myriad other applications.

However, polymer-based porous material design has been a challenge because of limitations in the materials, something that 3D printing and other new fabrication technologies have helped but not solved.

The graphic shows the concept of a new 3D-printing process that can control the porosity of polymeric materials. Researchers at Singapore University of Technology and Design (SUTD) developed the method. (Image source: SUTD)

Now researchers from Singapore University of Technology and Design (SUTD) have developed a new 3D-printing method to fabricate 3D porous models in one step, demonstrating for the first time that researchers can digitally control porosity in polymers, researchers said.

The approach researchers took is called immersion precipitation 3D printing, or ip3DP, and it allows for controlled deposit of materials, said Rahul Karyappa, a postdoctoral research fellow at SUTD who worked on the research.

In the new approach, researchers directly print inks containing polymers in a bath of a non-solvent, using immersion precipitation to solidify the ink rapidly, said Karyappa, who works in the Soft Fluidics Lab at SUTD. This spontaneous solidification via immersion precipitation generated porosity at micro-to-nano scales, he said.

“The polymer ink is directly dispensed in a non-solvent from a motion-controlled syringe,” he explained to Design News. “Immersion precipitation of the dissolved polymers occurred in situ when the ink was in contact with the non-solvent. In general, solvent extraction occurs much faster than solvent evaporation; ip3DP permitted the use of solvents with low vapor pressure such as water, DMF (dimethylformamide), and DMSO (Dimethyl sulfoxide).”

Diverse Materials, Diverse Uses

The wider selection of solvents in the process also gave researchers more freedom in the type of materials they could use, permitting a wider selection of thermoplastics to be printed, Karyappa told Design News. To demonstrate this, researchers fabricated centimeter-scale models in 13 polymers dissolved in six solvents, he said.

Researchers published a paper on their work in the journal Materials Horizons.

Overall, ip3DP permits a wide selection of printable materials by the selection of

the solvents applicable to the printing, researchers said. In particular, ip3DP enabled 3D printing of copolymers and polymer composites that have never been demonstrated for 3D printing, Karyappa told Design News.

“ip3DP permits 3D printing of responsive materials (hydrogels, shape memory polymers and elastomers) and powder materials (metal, glass and ceramic) suspended in solvents,” he told us. “ip3DP will offer unprecedented flexibility and pave avenues to fabricate biocompatible scaffolds, reinforced composites, and functional devices by 3D printing.”

Indeed, scientists already have found many uses for materials with controlled porosity. In materials science, they are used for separation and catalysis; in electronics, for sensors and actuators; and in medicine, tissue engineering and drug delivery.

Researchers plan to continue to develop the material library for the ip3DP method to expand the possibilities for porous materials that can be fabricated using it, Karyappa told Design News.

They also plan to “optimize printing conditions for the fabrication of 3D structures with controlled porosity,” as they envision “broad applications in material processing and biomedical engineering,” he added.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.