Researchers from the University of Washington (UW) have introduced a new way to 3D print mycelium-based biocomposites, sidestepping the need for traditional molds.
Led by Danli Luo, alongside Junchao Yang, and Nadya Peek this approach uses a specialized 3D printable paste called Mycofluid, a custom-built 3D printing system named Fungibot, and an incubation process that allows mycelium to grow within printed structures.
Published in the 3D Printing and Additive Manufacturing journal, the study highlights how this method could offer a more sustainable alternative to conventional fabrication without compromising on functionality.
Mycelium biocomposites offer structural strength and hydrophobic properties, but rigid molds limit design flexibility. Attempts with flexible formworks like knitting or weaving have led to uneven material distribution and structural inconsistencies, says the team.
“We’re interested in expanding this to other bio-derived materials, such as other forms of food waste,” Luo said. “We want to broadly support this kind of flexible development, not just to provide one solution to this major problem of plastic waste.”
A sustainable and affordable alternative
According to the team, 3D printing allows direct deposition of materials into custom shapes, reducing reliance on molds, but dense substrates hinder mycelium colonization.
That’s where Mycofluid comes in. This biopaste is made primarily of spent coffee grounds, making up 73% of its solid content, combined with brown rice flour for nutrients and xanthan gum for binding.
Its formulation balances granularity, viscosity, and efficient sterilization, making it a practical choice for 3D printing applications. Since spent coffee grounds are already widely used in small-scale mushroom cultivation, this method takes advantage of an abundant waste resource.
To print Mycofluid, the research team developed Fungibot, an open-source 3D printing system designed for moisture-sensitive biomaterials. It includes a material reservoir and a lightweight auger extrusion printhead, making it possible to control how the biopaste is deposited.
The entire setup costs about $1,700, far more affordable than commercial alternatives that can exceed $7,000.
Once printing was complete, the structures went through an incubation period where mycelium colonization takes place. The researchers selected Reishi (Ganoderma lucidum) grain spawn as the inoculating agent due to its resistance to microbial contamination.
Given the right conditions, proper moisture levels, air exchange, and low light, the mycelium spreads across the printed material, strengthening the structure as it grows.
One key feature of this approach is bio-welding, where living mycelium fuses separate printed parts, allowing complex geometries. Demonstrations included a Moai statue, stacked vase, and biodegradable packaging. A butterfly-sized mini-coffin was also printed to explore compostable applications.
Structural and mechanical performance
Physical and mechanical testing revealed some interesting results. Mycelium growth significantly improved hydrophobicity, creating a protective outer layer with a contact angle of 138°, which helped resist water absorption.
In contrast, uncolonized structures absorbed 65% of their weight in water, while colonized biocomposites absorbed only 7%, maintaining their shape and durability.
Strength and flexibility shifted as well. Uncolonized Mycofluid structures recorded the highest tensile strength at 3.21 MPa, which dropped to 1.41 MPa after colonization. However, elongation at break doubled from 0.4% to 0.8%, meaning the material became more flexible rather than brittle.
Compression tests showed that colonized biocomposites exhibited higher toughness compared to coffee-based biocomposites without mycelium, which fractured more easily.
The findings suggest that mycelium-based 3D printing could be a viable alternative to traditional mold-based fabrication. Removing the need for rigid molds expands design possibilities, while bio-welding opens up new ways to create larger, adaptable structures with minimal waste.
That said, the process isn’t without its challenges. Maintaining sterility during printing and incubation is crucial to prevent contamination. Freshly printed Mycofluid structures remain delicate during this phase, requiring careful handling to avoid deformation. Additionally, print quality is influenced by material consistency and extrusion accuracy, making precision an essential factor in the process.
Although the study didn’t formally test compostability, prior research suggests Mycofluid’s ingredients are biodegradable. However, production remains slow, with mycelial colonization taking over a week, limiting its scalability for now. To address this, researchers plan to explore faster incubation methods, a broader range of biomass substrates, and automated quality control to refine the process.
Lastly, the researchers emphasize that this is just the beginning of exploring mycelium’s role in customized manufacturing and biodegradable materials.
Bio-based 3D printing research
Away from UW, other institutes also contributed to bio-based 3D printing. For instance, Vilnius University and Kaunas University of Technology researchers developed a recyclable bio-resin using soybeans for Optical 3D Printing (O3P).
This material met the technological and functional requirements of traditional 3D printing polymers while providing greater biocompatibility at a lower cost. By incorporating soybean extracts, the resin facilitated small-batch production and aimed to reduce reliance on non-recyclable petroleum-based photopolymers.
Back in 2021, Nanyang Technological University (NTU) researchers developed a sunflower pollen-based bio-ink for bioprinting, offering both structural integrity and versatility for biomedical applications. Combining pollen microgel with alginate and rubber, this hybrid ink can be fine-tuned to create stable, multi-layered cell scaffolds and drug delivery systems.
Leveraging pollen’s unique properties, the team addressed challenges like print collapse and nozzle clogging while producing flexible, biocompatible materials. The findings suggested that this eco-friendly ink could yield cost-effective, custom biomedical devices such as wound patches and facial masks that contour to human skin.
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Featured image shows the packing material around this small glass was 3D printed from used coffee grounds. Image via UW.
