3D printed structure degrades on demand

Researchers at Brown University have developed a technique to make 3D printed biomaterials that degrade on demand. We interviewed Thomas Valentin, the study’s lead author.

In your research you developed the degradable structures using stereo lithography. Can you explain how this 3D printing technology works?

Stereo lithography is a type of 3D printing that uses photochemistry and a laser to trigger local cross linking of the polymer in a layer-by-layer approach.

Are there any restrictions in stereo lithography in terms of size and shape of the structures that it can create?

Standard stereo lithography machines require large amounts of resin (up to 45L), so we customized our printer to work with 300mL of resin. The minimum feature size is dictated by the laser beam diameter (~80um for our printer).

How was the technique adjusted to make degradation on demand possible?

Degradation was triggered using ethylenediaminetetraacetic acid (EDTA), which chelated / removed the cations from the alginate network, thereby degrading the printed structure.

What polymers were used in the experiment to build the structures?

We used a 3% (w/v) alginate formulation to fabricate the structures.

To what extend is it possible to vary the strength and stiffness of the structures?

The stiffness can be modified by post-curing the structure using a high-concentration cation salt solution (BaCl2, CaCl2, etc.). However, you will only be able to increase the stiffness until all of the alginate guluronate groups are occupied. At that point, adding more cations will not make a difference. You would need to increase the starting concentration of alginate to add more cations.

Can the pace of degradation also be varied? 

The rate of degradation can be varied by increasing the concentration of the chelator (EDTA), increasing the temperature at which the structure is degraded, by varying the concentration of and the type of cation used to cross link the alginate, and by varying the starting concentration of alginate.

Are the structures bio compatible?

The structures are very bio compatible. We saw very high cell viability in our cell migration experiments (see supplemental information).

What do you think are the possible applications for the degradable structures? We demonstrated applications for micro fluidic fabrication, collective cell migration, and we hope to explore its use as a sacrificial support material in fabrication of more complex 3D parts.

What will be the next steps in your research?

We are exploring methods to improve the pattern fidelity and mechanical properties of these hydro gels, and hope to print self-supporting, elevated structures.

Video: courtesy of Thomas Valentin, Brown University