Week 10: Biofabrication and additive manufacturing


In this class, Fiorenzo Omenetto and Benedetto Marelli from SilkLab at Tufts University, described how we can use naturally derived materials for making and building. The guiding principle is to reinvent structural biopolymers into high-technological materials through basic principles of materials science, advanced fabrication and ingenuity. The class will be focused on silk and keratin, materials with thousands of years of history and that now can be engineered to serve at the interface between the biotic and abiotic world. The natural origin of biopolymers also allows for the engineering of materials with remarkably low-energy processing and little environmental impact. By discussing biopolymer regeneration, self-assembly and advanced fabrication we will not only explore a material platform technology at the interface between innovation and sustainability but also introduce a biomaterials based approach that can operate between growing anything and making anything.

Lab Homework Assignment - Extract Silk fibroin!

Fig. 1: Regeneration of silk fibroin into an aqueous suspension (Refer to Step 1-23 in Rockwood et al. Nature Protocols, 6, 1612–1631 (2011)).

Pre-step! Making Baking Soda (Sodium Bicarbonate, NaHCO3)into Washing Soda (Sodium Carbonate, NaCO3). Heating at 400 degrees does the job to pop off that extra hydrogen.

Cutting the cocoons into small pieces.

We boiled the cocoons for 30 min in our 0.02 M Washing Soda solution. This denatures the outer seracin coating that adheres the two fibroin strands together. Thus, a few rinses and drying and we've got a big fluffy knot!

Preparation of the Lithuim Bromide (LiBr) required us to brush off some old stocheometry; also- exothermic, it should be prepared on ice. Next, the addition of LiBr to our tightly packed silk to solubilize the proteins.

Here you can see the before and after LiBr chemical reaction. The silk fibers are completely dissolved.

During 4 hr incubation, the silk disolves into a golden syrup. We must inject this into a dialysis cassette, and filter via submersion in DI water for 48 hours.

Cleaned up, the biopolymer is ready to rock. It can be poured out into flat sheets (below). It can pick up the fine grooves of a hologram or even loaded into a addative printer.