Biopolymer-based inks and use thereof

A printable keratin ink comprising:

• an aqueous keratin solution, substantially free of an organic solvent and having a molecular weight of about 3.5 kD to about 350 kD and a concentration of keratin in a range of about 0.1 (wt/vol) % to about 10 (wt/vol) %;
• wherein when it is printed to a substrate, a droplet volume of about 0.1 pL to about 5 nL of the aqueous keratin solution is characterized by a viscosity of about 1 centipoise to about 20 centipoise when viscosity is measured at room temperature and a surface tension of about 15 dynes/cm to about 50 dynes/cm when measured at room temperature.