From customized hearing aids to complex dental implants, 3D printing has transformed how we make finely detailed products. However, there is a major problem with this promising technology that is rarely discussed. 

During 3D printing, to keep the printed object stable, temporary support structures are fabricated along with the final product. Made from the same material as the product, these supports must be manually removed after printing. This process is time-consuming, delicate, and generates a lot of waste that can’t be reused.

For quite some time, scientists have been scratching their heads to solve this problem. Finally, a new study from MIT researchers proposes a practical solution that could dramatically reduce the time, effort, and waste involved in 3D printing.

The study reveals a peculiar light-sensitive resin that can easily solidify and dissolve whenever required, making it easy to remove the supports and recycle them for future use. Here is how the MIT team developed this material.

Cracking the problem of waste in 3D printing

In one version of 3D printing, a model is built layer by layer using light to harden a liquid resin, this process is called vat photopolymerisation. However, once the conventional resin hardens, it stays solid and can only be removed by manually chipping it away.

To tackle this, MIT researchers developed a resin that behaves differently under two kinds of light. The team started by mixing two readily available chemicals (IBOA and EPOX), called monomers, which are building blocks of plastics. 

When this mixture is exposed to UV light, the monomers form tight chemical bonds, producing a hard, durable solid. However, when the same resin is exposed to visible light (like from an ordinary LED), it forms a softer solid with loosely connected strands.

This soft solid can easily dissolve in gentle solvents, including baby oil or even the original liquid resin itself. Initially, when they tested this resin in a small lab setup, it worked as planned: one material became tough and the other, dissolvable. 

However, when they tested it in a real 3D printer using dimmer LEDs, the hard parts weren’t holding up; they were falling apart in solution. To fix this issue, the team added a third ingredient, a special “bridging monomer” (3,4‑epoxycyclohexylmethyl acrylate, aka ECHA) that helped link everything tightly when UV light was used, creating a sturdy final product.

Using the modified resin, the researchers could now print both the main object and its supports at the same time using different light patterns. Once the printing was done, they simply dipped the structure into a solution that dissolved the supports; no clipping or breaking was required. Even better, the dissolved material could be recycled into fresh resin for the next print job. 

They named their approach selective solubility vat photopolymerization (SSVP) and employed it to 3D print complex shapes like gear trains, lattices, and even a small dinosaur inside an egg — the kind of design that would be nearly impossible to create in a waste-free manner using traditional methods.

“This shows we can print multipart assemblies with a lot of moving parts, and detailed, personalized products like hearing aids and dental implants, in a way that’s fast and sustainable,” Nicholas Diaco, lead researcher and a PhD candidate at MIT, said.

A step towards making 3D printing sustainable

While 3D printing is often better than conventional fabrication and construction methods, it is not entirely an eco-friendly technology. For instance, a report suggests that 33 percent of all 3D printed structures (supports) form waste, and most of them end up in landfills, causing harm to the environment. 

“For the most part, these supports end up generating a lot of waste,” Diaco said.

Moreover, traditional methods, like Filament-based 3D printing, which is a popular 3D printing approach in the UK and many other countries, generate thousands of kilograms of plastic waste each year.

The newly developed resin opens the door to faster, cleaner, and more efficient 3D printing technology. By eliminating the need to manually remove supports and reducing material waste, the process could become more scalable and eco-friendly. 

The next step would be to test SSVP with a wider variety of materials, especially ones that are strong enough for industrial or long-term use. The researchers also plan to develop other resins with similar dual behavior and work on automating the recycling of the waste so that the entire system becomes self-sustaining.

The study is published in the journal Advanced Materials Technologies.