May 27, 2016 | By Kira

A team of Autodesk researchers and dedicated UC Berkeley students has released a report outlining three key approaches to improving the safety and sustainability of SLA 3D printing materials by asking “what would nature do?" The findings point to several naturally-derived materials that can replace toxic elements found in today's commercial resins.

Image of electrospun chitosan fiber strand via msaustero & Autodesk

While 3D printing is opening many doors for modern manufacturing—producing previously unimaginable geometries in record time and with little material waste—the undeniable drawback is that many 3D printing materials, and SLA resins in particular, are toxic to both humans and the environment.

“Products manufactured using 3D printing should be safe for humans and the environment throughout their lifespan: during their production, use, and disposal. Unfortunately, the chemical hazards associated with many of today’s SLA 3D printing materials present considerable drawbacks in all these areas,” explain Michael Floyd and Susan Gladwin of Autodesk, which sponsored the research.

“The development of ‘biofriendly’ materials—that are safe and sustainable—for 3D printing will allow for new use cases and open up whole new markets. Solving this piece of the puzzle is therefore critical to unlocking AM’s larger potential.”

The report begins with a health and hazard assessment of the 3D printing resins used in Autodesk’s Ember SLA 3D printer, as well as other commercially-available SLA resins. This assessment found that even after the polymerization process (where the resin is hardened via a UV light source), residual resin remains. This resin is considered a toxic, hazardous waste, and can cause sensitization over time, leading to increasingly harmful reactions in humans, including asthma and skin rashes.

Autodesk Ember SLA 3D Printer

In order to find an alternative, non-toxic formula (or formulas), the researchers focused on the concept of biomimicry that is, borrowing ideas from the natural world and applying them to technological development. The theory is that nature itself already provides the most efficient, sustainable and beneficial materials and processes, so why try to replace them with toxic and limited man-made 'solutions'?

Specifically, the team began with PR48, also known as Autodesk’s Standard Clear Prototype Resin. Using PR48 as a starting point allowed the researchers to isolate exactly which elements within the resin were hazardous, and devise a way to replace or eliminate them.

The offending elements turned out to be PR48’s photoinitiator and its acrylate-based monomer, both of which present hazards to human health and the environment. Following this, they came up with three approaches to improving the hazard profile of PR48 and similar SLA 3D printing resins:

  1. Replace the photoinitiator
  2. Modify the resin acrylates
  3. Create an entirely new resin

For example, naturally-derived food additives, such as curcumin and riboflavin (vitamin B2) can be used in tandem as a photoinitiating system, replacing the toxic TPO used in PR48 today.

As for the acrylates, which make up roughly 99% of PR48 by weight, these can be modified by increasing their molecular weight, decreasing their ability to be absorbed into the skin. For this, the researchers proposed using alcohol-containing triglycerides (fats) derived from castor oil, or chitosan, which can be derived from shrimp shells.

According to Floyd and Gladwin, these first two approaches are considered ‘incremental changes’ to the PR48 formulation: “These alternative bio-based components have the potential to be more sustainably sourced than their petroleum-based counterparts, which are currently used in commercial SLA resins. When used in combination, these incremental changes could increase safety and decrease costs, thus lowering hazards significantly and enabling new applications.”

Chitosan, derived from Chitin, can be found in shrimp shells and used as an alternative SLA material component

The third option, however, demands a complete overhaul: the development of entirely new SLA resin formulations that go beyond acrylates and are rooted in biological systems.

For example, two alternative formulations are inspired by the oyster and the mussel. “These species adhere to rock under tremendous force from moving seawater. We can learn from both their process and their materials as it relates to SLA additive manufacturing. These organisms take advantage of the pH change in the seawater to form adhesive cement. This cement forms filaments known as 'byssus', which these mollusks use to anchor themselves to solid surfaces” they explain.

By developing a photoactive resin that mimics the proteins excreted by mussels, the researchers believe they could create a resin that actually allows for different material properties within a single 3D print. “Producing a technology that can span a range of material properties within a single print, with micron layer precision, would represent a significant advancement in SLA technology.”

Clearly, there are extremely interesting materials and processes happening in the natural world that can not only improve the toxicity of SLA 3D printing, but advance its technological possibilities as well.


“This is an exciting, uncharted area of exploration that could change additive manufacturing greatly. It represents an opportunity to additively manufacture in a process much closer to biological systems,” said Floyd and Gladwin. “We hope that by sharing insights from this collaboration, we can foster the development of innovative SLA resins that are safer and healthier for people and for our planet.”

The research was carried out by Autodesk experts, including Chris Venter of the Bio/Nano team and Brian Adzima of the Digital Manufacturing Group, as well as the Fall 2015 University of California Berkeley Greener Solutions class at the Center for Green Chemistry (BCGC). The details of the report can be found in Autodesk Spark's three-part series, or in the final Autodesk Green Resin Project report.



Posted in 3D Printing Materials



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