Chitosan Biofilm Actuators: Humidity Responsive Materials for Sustainable Interaction Design

Shape-changing interfaces have been critiqued for not being sustainable despite their promising opportunities for tangible interaction. Incorporating nature inspired passive actuation mechanisms with embedded responsiveness can offer benefits for shape-changing interfaces. We introduce chitosan, a widely available biodegradable and humidity-responsive actuator that absorbs moisture from air and undergoes shape changes in response to fluctuations in humidity. Through explorative yet systematic material driven research through design, we uncover the utility and accessibility of chitosan as a reversible actuator to enable interactivity. We present the characterization of a variety of responsive structures made from chitosan films, combined with a variety of substrates. Outcomes from a generative session with designers/engineers from diverse backgrounds, provided insights into experiential properties and possible applications. We conclude with early prototypes that hold potential for wearables, haptics, self-assembly, and data-physicalization.