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Abstract Herein, a method that uses direct‐ink‐write printing to fabricate engineering living materials (ELMs) that respond by undergoing a programmed shape change in response to specific molecules is reported. Stimuli‐responsiveness is imparted to ELMs by integrating genetically engineered yeast that only proliferate in the presence of specific biomolecules. This proliferation, in turn, leads to a shape change in the ELM in response to that biomolecule. These ELMs are fabricated by coprinting bioinks that contain multiple yeast strains. Locally, cellular proliferation leads to controllable shape change of the material resulting in up to a 370% increase in volume. Globally, the printed 3D structures contain regions of material that increase in volume and regions that do not under a given set of conditions, leading to programmable changes in form in response to target amino acids and nucleotides. Finally, this printing method is applied to design a reservoir‐based drug delivery system for the on‐demand delivery of a model drug in response to a specific biomolecule. 

Stimuli-responsive materials are able to undergo controllable changes in materials properties in response to external cues. Increasing efforts have been directed towards building materials that mimic the responsive nature of biological systems. Nevertheless, limitations remain surrounding the way these synthetic materials interact and respond to their environment. In particular, it is difficult to synthesize synthetic materials that respond with specificity to poorly differentiated (bio)chemical and weak physical stimuli. The emerging area of engineered living materials (ELMs) includes composites that combine living cells and synthetic materials. ELMs have yielded promising advances in the creation of stimuli-responsive materials that respond with diverse outputs in response to a broad array of biochemical and physical stimuli. This review describes advances made in the genetic engineering of the living component and the processing-property relationships of stimuli-responsive ELMs. Finally, the implementation of stimuli-responsive ELMs as environmental sensors, biomedical sensors, drug delivery vehicles, and soft robots is discussed. 

This work establishes a means to exploit genetic networks to create living synthetic composites that change shape in response to specific biochemical or physical stimuli. Baker’s yeast embedded in a hydrogel forms a responsive material where cellular proliferation leads to a controllable increase in the composite volume of up to 400%. Genetic manipulation of the yeast enables composites where volume change on exposure to l -histidine is 14× higher than volume change when exposed to d -histidine or other amino acids. By encoding an optogenetic switch into the yeast, spatiotemporally controlled shape change is induced with pulses of dim blue light (2.7 mW/cm 2 ). These living, shape-changing materials may enable sensors or medical devices that respond to highly specific cues found within a biological milieu.