By leveraging the unique qualities of microorganisms, engineered living materials (ELMs) offer functional and economic advantages in everyday applications along with notable ecological benefits. This study contributes to the growing field of biodesign by examining the potential of Flavobacteria for thermochromic ELMs. Many Flavobacteria, commonly found in marine environments, produce iridescent structural colorations as their colonies expand on semi-solid surfaces through gliding motility. In this study, we analyzed the effects of temperature variations on flavobacterium Cellulophaga lytica PLY-A2, characterizing distinct changes in colony growth and iridescent colorations at a macroscopic and microscopic scale. Using scanning electron microscopy, we investigated the relationship between iridescent color and the underlying cell-based optical structures. By providing insights into the temperature-responsive behavior of Flavobacteria, our findings highlight their potential for future thermochromic ELMs—with applications ranging from sustainable food packaging to smart textiles—while encouraging further characterization studies within biodesign research.

This dissertation presents an in-depth exploration of iridescent Flavobacteria, integrating laboratory characterisation, design-led experimentation, and a longitudinal study of everyday engagement. It shows how their living colour unfolds over time, captures external conditions, and opens space for relational dynamics and reflection on interconnectedness between microbial life, humans, and their surroundings. The work develops knowledge, tools, and approaches that support designing living artefacts for everyday human–microbe engagement.

HCI designers increasingly engage in the integration of microbes into artefacts, leveraging their distinct biological affordances for novel interactions. While in many explorations the interaction between humans and microbes is mediated, scholars also highlight the potential of direct interactions, such as visualising mechanical distortions or fostering a sense of relationality with nonhumans through eliciting intimate encounters. Seizing upon this potential, our study delves into the realm of direct interactions involving Flavobacteria, recently introduced as a colour-changing interactive medium in HCI. We present a design space for direct interactions where humans can (re)activate, (re)direct, and (re)arrange Flavobacteria’s colourations, thereby fostering a personal and dynamic interplay between humans and microbes. With our work, we aspire to provide pathways and ignite inspiration among HCI designers to create living artefacts that cultivate active engagement and heightened attentiveness towards microbial worlds and beyond.

In recent years, there has been a notable proliferation and diversification of works in HCI, that integrate living microorganisms; an imperative lifeform dominating ecosystems of our planet. Yet despite the growing interest, there is a lack of structured lenses with which designers can strategize their processes of surfacing livingness; a material quality inherent in living artefacts with a potential to enrich user experiences and to initiate mutualistic care between humans and microorganisms. Through a systematic artefacts review and a case study on Flavobacteria, we have developed and instantiated a Taxonomy of Surfacing Livingness in Microbial Displays, consisting of six microbe-sensitive, tuneable mechanisms for human noticing of microorganisms: 1) Canvassing, 2) Marking, 3) Magnifying, 4) Translating, 5) Nudging, and 6) Molecular Programming. The taxonomy invites diverse and adaptable ways of generating and crafting microbial displays; towards overcoming microbe-specific surfacing constraints, integrating diverse stakeholders' values, and enabling nuanced address of microbial welfare.

Flavobacteria, which can be found in marine environments, are able to grow in highly organized colonies producing vivid iridescent colorations. While much is known about the biology of these organisms, their design potential as responsive media in user interfaces has not been explored. Our paper aims at bridging this gap by providing insights into the type, degree, and duration of change in Flavobacteria's expression, i.e., their living aesthetics. We present a tool to capture and characterize these changes concerning form, texture and iridescent color. To support the long-term study of their living aesthetics, we designed Flavorium. This bio-digital artifact provides the necessary habitat conditions for Flavobacteria to thrive for a month. Granting insights into the responsive behavior of this organism, this work presents a design space, vocabulary, and application concepts to inspire HCI and design scholars to investigate the complex temporal qualities of living media for future user interfaces.