Researchers at the Singapore University of Technology and Design (SUTD), under the leadership of Associate Professor Michinao Hashimoto, have introduced a new technique for 3D printing electrically conductive structures using eco-friendly materials. By merging immersion precipitation with direct ink writing (DIW), they successfully produced robust and accurately shaped components from a composite of cellulose acetate and graphite.
Cellulose acetate is a biodegradable, bio-based plastic. However, its low thermal resistance makes it unsuitable for conventional techniques like fused deposition modeling (FDM), which require high temperatures. To address this, the researchers devised a room-temperature process. They created a custom ink by dissolving cellulose acetate in acetone and mixing it with graphite particles. This ink is then extruded into a water bath, where it solidifies instantly due to the rapid diffusion of acetone into the water.
“As 3D printing advances, the technology isn’t just about shaping plastics anymore,” said Associate Professor Hashimoto. “It’s also about weaving in functionality, such as conductivity, to create devices directly from sustainable materials. This is the first time immersion precipitation and 3D printing have been combined to realize conductive polymer composites. It lets us print inks with a much higher filler content than usual, without clogging or structural collapse.”
Performance and Applications
This method addresses typical issues encountered with high-filler-content inks, such as uncontrolled spreading and nozzle clogging. By incorporating as much as 60% graphite by weight, the team produced stable structures with electrical conductivities above 30 S/m—sufficient to operate low-power electronics. To showcase the material’s functionality, they printed conductive tracks capable of lighting LEDs. Additionally, the researchers fabricated complex and freestanding structures within a gel-based support bath, allowing for greater geometric freedom and design versatility.
“By tuning the material properties and refining the process, we aim to build a full library of printable, functional composites tailored for specific applications—whether it’s wearable tech, biosensors, or flexible circuits,” said Hashimoto.
Future Directions
Looking ahead, the SUTD team aims to expand their work by experimenting with a broader range of polymer–filler combinations and further refining their printing technique. Their long-term vision is to develop a scalable, resource-efficient platform for producing sustainable electronic components—one that reduces or eliminates the need for post-processing while maximizing both functional performance and design flexibility.
Innovations in Cellulose-Based 3D Printing
In addition to SUTD’s development, other researchers at MIT have also advanced cellulose-based 3D printing. In 2021, MIT scientists Dr. Sebastian Pattinson and Prof. A.J. Hart introduced a method for 3D printing cellulose acetate (CA), a cellulose derivative commonly found in cigarette filters, as an eco-friendly alternative to conventional plastics. They successfully printed complex shapes that exhibited toughness 46% higher than the original CA and outperformed materials like ABS, PLA, and certain nylon fibers. The addition of antimicrobial dyes further enabled the printed parts to reduce E. coli bacteria by 95% under light exposure, demonstrating potential for producing strong, flexible, and antibacterial components suitable for medical devices.
Elsewhere, researchers at the Swiss Federal Laboratories for Materials Science and Technology (EMPA) have used 3D printing to create a sustainable new class of supercapacitor. The fully-3D printed battery, composed of a flexible cellulose and glycerol substrate, patterned with a conductive carbon and graphite-laden ink, is able to withstand thousands of charging cycles while maintaining its capacity. Thanks to its biodegradable base, the novel cell can also be composted once finished with, potentially making it an ideal tool for tackling the world’s electronic waste issues.
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Featured image shows Use of 3D printed conductive structures to power an LED circuit, with panel (a) showing the circuit diagram and panels (b–d) displaying various CAD designs. Image via ACS.
