3D printing, also known as additive manufacturing (AM), has become one of the most significant technological advancements in recent years, enabling the creation of complex structures with high precision. However, a major concern about the vast majority of current photoresins used in 3D printing remains their environmental impact. These resins, typically derived from petroleum-based sources, are toxic, non-biodegradable, and rely on unsustainable feedstocks. Furthermore, they often contain harmful chemicals such as monomers that pose significant hazards to both human health and the environment.
Addressing these concerns, researchers have turned to non-traditional approaches for 3D printing that step away from conventional, unsustainable chemical methods and instead focus on sustainable, safe materials. One promising innovation comes from a collaboration between Prof. AJ Boydston from the Department of Chemistry at the University of Wisconsin and Prof. Audrey Girard from the Department of Food Science. Their groundbreaking work focuses on the use of protein denaturation as a new method for 3D printing, presenting an exciting and environmentally friendly alternative to traditional photoresins. This new technique is outlined in their paper published in Green Chemistry.
Breaking Away from Petroleum-Based Resins
The need for sustainable and non-toxic alternatives in 3D printing has never been more urgent. With growing concerns over plastic waste, the environmental and health impacts of petrochemical-based products, and the need to transition to a circular economy, researchers are increasingly exploring eco-friendly options. While some advances in biodegradable plastics have emerged, few are suitable for the precision and versatility offered by 3D printing. In this context, protein-based materials offer an exciting alternative. Proteins, abundant in nature and biodegradable, could represent a solution to the issues posed by the current state of 3D printing resins.
To explore this potential, Boydston and Girard developed the innovative concept of Additive Manufacturing via Protein Denaturation (AMPD), using a technique that allows for the fabrication of 3D-printed objects from aqueous protein solutions. Unlike conventional resins that require harsh chemicals or cross-linking agents, AMPD relies on the natural process of protein denaturation to solidify materials into intricate 3D shapes. Denaturation occurs when proteins lose their native structure due to changes in temperature or pH, causing them to unfold and aggregate. This process creates a solid, thermoset-like material without the need for additional toxic reagents.
The Innovation of HAPPI 3D Printing
The key to making this new protein-based 3D printing method feasible lies in a cutting-edge process known as Heating at a Patterned Photothermal Interface (HAPPI 3D). This approach, invented by Boydston and Dr. Chang-Uk Lee (a member of Boydston’s research group), leverages photothermal transduction to convert patterned light into heat, allowing for precise control over where and how heat is applied to the protein resin. By carefully manipulating the heat distribution through controlled light patterns, the team can effectively induce protein denaturation in specific areas of the resin.
On a practical level, this means that with HAPPI 3D printing, 3D shapes can be rapidly constructed layer by layer, with heat being used as the catalyst to solidify the protein-based resins. This method is both energy-efficient and highly adaptable, offering numerous advantages over traditional chemical-based processes that typically require additional harmful agents or curing steps.
Successful Demonstration of 3D Protein Printing
In their proof-of-concept demonstration, Boydston and his team, including undergraduate researcher Sung June Kim and postdoctoral researcher Dr. Rachel Dietrich, used protein-based resins for 3D printing, which were derived from natural, non-toxic feedstocks. Unlike typical resins made from synthetic polymers, these proteins were sourced from food-grade materials—one example being proteins derived from plant-based foods. This not only provides a safer option for the manufacturing process but also ensures that the resultant products are biodegradable.
The team was able to successfully print complex, three-dimensional objects from these protein resins by using the AMPD approach, where heat generated from patterned light caused the proteins to denature, leading to solidification of the structure. The mechanical properties of the printed objects were comparable to commodity plastics such as polyethylene and polystyrene. By adjusting the concentration of the protein in the resin, they were able to precisely control the porosity of the printed objects, opening up possibilities for diverse applications that require specific material properties, such as lightness, flexibility, or strength.
Biodegradability and Sustainability
One of the most significant breakthroughs of the team’s approach is the biodegradability of the resulting 3D-printed parts. The proteins used are naturally occurring and do not require any harmful chemical modifications to be 3D printable. This means that objects created with this technique will naturally break down in the environment over time, reducing the long-lasting pollution associated with plastic waste. This stands in stark contrast to conventional plastic-based 3D printing materials, which, despite their wide use, persist in the environment for hundreds of years, contributing to the growing problem of plastic pollution.
Additionally, the sustainability of this method extends beyond biodegradability. The proteins used in these 3D printing processes can be derived from a variety of sustainably sourced feedstocks, such as plant-based proteins, which are far more renewable than petroleum-based products. This significantly reduces the carbon footprint associated with manufacturing 3D-printed materials.
Applications in Healthcare: Bioresorbable Scaffolds
Looking ahead, Boydston and his colleagues are particularly excited about the potential of this new material in the field of biomedical engineering. One of their most promising future applications is the development of bioresorbable tissue scaffolds for medical use. These scaffolds could be custom-designed with patient-specific geometries using 3D printing techniques. These scaffolds would support the growth of new tissues and promote regeneration inside the body, while gradually degrading over time, leaving no trace behind once their function is complete. For example, bioresorbable scaffolds could be used in orthopedic implants or as a foundation for wound healing.
This approach could transform the field of regenerative medicine, providing patients with materials that not only serve to aid healing but also contribute to the sustainable and ethical production of medical devices. By using a material that’s both biodegradable and sourced from renewable biological sources, the medical field can move towards a more sustainable, patient-friendly solution.
Expanding the Horizons of 3D Printing with Protein Resins
The team’s work on protein-based 3D printing has wide-ranging implications. In addition to healthcare applications, the sustainable nature of the technique makes it viable for a host of other sectors, including packaging, construction, and consumer goods. Since these proteins can be derived from renewable sources, and since the AMPD method reduces energy use and chemical inputs, the environmental benefits could extend far beyond the printing laboratory.
Future research will focus on further improving the technology to expand its scope of applications. The team plans to explore other types of proteins for resin formulation, allowing them to optimize specific properties depending on the desired applications—such as protein resins from different plants, animal-based proteins, or even industrial waste products that can be turned into useful materials. There is also the potential to work on scaling the process and increasing the speed of the 3D printing system, enabling large-scale production while maintaining sustainability.
Conclusion: Paving the Way for a Greener Future
The successful development of Additive Manufacturing via Protein Denaturation (AMPD) represents a significant step forward in the evolution of 3D printing technology. By utilizing proteins in a non-toxic, biodegradable form, Boydston and Girard’s team has established a process that not only offers potential for sustainable manufacturing, but also holds promise for solving pressing healthcare challenges. With its ability to convert natural proteins into solid 3D parts via heat-induced denaturation, this new method significantly reduces reliance on environmentally harmful resins while providing a platform for future biomedical applications.
As research continues and new protein feedstocks are explored, the possibilities for greener, more sustainable 3D printing technologies will only expand, enabling more eco-conscious and health-focused applications. The future of 3D printing could look very different—more sustainable, efficient, and beneficial to both people and the planet.
Reference: Chang-Uk Lee et al, Additive manufacturing via protein denaturation, Green Chemistry (2024). DOI: 10.1039/D4GC02932A