Nature uses proteins for a variety of functions, such as for making high-hierarchical structures and in mediating charges. In our work, we are inspired by nature and utilize proteins as building-blocks for making conductive biopolymers. Having a sustainable approach, we focus only on proteins that can be produced in bulk quantities and at low cost from raw materials. Most of our work to date has been focused on the bovine serum albumin (BSA) protein, which is essentially a waste product of the extensive bovine industry, hence utilizing it for making new materials promotes its circular use. We show that using our newly designed (bio-)polymerization approach we can form free-standing (self-supporting) and insoluble materials on the macroscale, having a. highly elastic nature, capable of stretching more than 5 times their length. The water uptake of our protein-based polymers and the presence of many amino acid residues that can participate in hydrogen bonding promote good ionic conductivity across the polymer. Following the formation of the biopolymer, we show that it can be further functionalized in different ways. For enhanced protonic conductivity we add oxo-acids to the polymer, resulting in measured ionic conduction of &gt;10mS/cm. For enhanced electronic conductivity we can dope the formed polymer with natural electron-mediating small molecules. For gaining new light-stimuli-responsive we attach to the polymer light-responsive molecules, resulting in light-attenuation of its electrical properties. Our new protein-based biopolymers have several attractive properties for their integration in various applications. Our materials are environmentally friendly, they possess inherent biodegradability and biocompatibility, they have attractive mechanical properties, and their formation obeys most principles of green chemistry. From a practical point of view, we introduce here an easy energy-efficient polymerization method without any synthesis. Moreover, due to the low price-tag of our chosen proteins and the simple formation process, the cost of our new biopolymers can reach merely 1USD for 100cm<sup>2</sup> of the final polymer. Currently, our main targeted application for our new family of materials is for biological interfaces, and we show their use in biosensing applications, while other lines of applications include the use of our biopolymers for biomedical applications (tissue engineering) and energy applications such as membranes for fuel cells.

Proteins as sustainable building-blocks for making large scale (bio-)polymers capable of mediating charges

ACS Spring Meeting 2021

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