Dong Li1 Marimikel Charrier1 Sneha Jani1 Wei Li1 Travis Massey3 Victor Mann1 Michel Maharbiz3 Kathleen Ryan2 Caroline Ajo-Franklin1 Paul Ashby1

1, Lawrence Berkeley National Laboratory, Berkeley, California, United States
3, University of California, Berkeley, Berkeley, California, United States
2, University of California, Berkeley, Berkeley, California, United States

Despite the unlimited potential for intelligent materials that can change their functionalities in response to various environmental cues, significant challenges still present for precisely controlling the material formation under different length scales. We report here the design and synthesis of a nacre-mimicking, hybrid material with tunable porosity and toughness using bacteria as the patterning and self-regenerating template. Caulobacter Crescentus is a Gram-negative, oligotrophic bacterium with exceptional strong surface binding and dense biofilm forming abilities. They can survive in a nutrient poor habitat for weeks. The outmost part of their cell envelope is covered by a monolayer of 2D crystalline proteins. This so-called S-layer is self-assembled from identical protein monomers of RsaA into hexagonal arrays with many functional residues exposed in a precisely repetitive manner. Taking advantage of these unique properties of C. Crescentus and its s-layer, a hierarchically-ordered, brick-and-mortar composites is created through programmed multicellular patterning between bacterial cells and silicon microplatlets. Selected elastin like peptides (ELPs) expressed by C. Crescentus were displayed on its s-layer protein arrays and cross-linked into a hydrogel network. The porosity and toughness of the hybrid material are reversibly controlled by temperature induced phase transition of ELP domains.