The bio-future was made small enough to hold, and warm enough to need you.
The green, sleek visions of more-than-human futures propose a profound shift in how we relate to microorganisms, and they stay on the shelf of theory because nobody can hold one. KojiGotchi is a wearable that keeps a living koji culture, Aspergillus oryzae, alive on the wearer's body heat. Neglect or attention decides the fate of the organism and the function of the device. It went to the Biodesign Challenge finals in New York in June 2025.
The Biodesign Challenge asks student teams to develop a biodesign project over a year. Our team at the Royal Danish Academy and DTU set itself the problem of sharing the bio-future's ideas with our own families and friends, past the elitist barrier of its narratives.
The Tamagotchi once introduced us to portable, attention-demanding technology and unknowingly prepared us for the mobile world. The same format, universally known and triggering no adverse reaction, could ease people into nurturing a living thing.
A working bioelectronic wearable with a growth chamber, temperature, humidity, CO₂ and VOC sensing and an avatar, the KojiMoji, that reflects the culture's state; a two-part user study; experiments showing body heat sustains koji; the finals in New York, a feature in Algae Magazine and the iGEM Art & Design exhibition.
Living wearables become everyday products, and people learn the care they need the way a generation learned to look after a Tamagotchi.
Koji was the organism for three reasons. Rice and koji spores can be ordered online and the result, fermented food, is something anyone can relate to. Its ideal growth temperature, twenty-five to thirty-five degrees, matches the surface of the human body, so the wearer practises care by literally entering a symbiosis, keeping it like an egg. And its livingness is surfaced by smell, which gives immediate sensory feedback on how well the care is going.
The device holds the culture in a growth chamber against the skin, with probes for temperature and moisture, a sensor for air temperature, humidity, CO₂ and volatile compounds, an aroma dispenser and a small screen. Some radical biodesigners criticise proxy interfaces that mediate between human and biology; I believe a step-by-step learning process is essential, so the device gives partial direct engagement, through metabolic symbiosis and smell, and a digital interface that helps the wearer read the subtle cues koji gives.
Biodesign is a shift in how we see our place in the world, away from the idea that humans control nature and toward life itself as a guide for design, objects that are partners rather than tools. The project came out of a personal frustration: the difficulty of sharing any of that with our own families and friends. The complex narratives around it create an elitist barrier, and the team formed specifically to get past it, to bridge the gap between abstract principles and something you can carry in your pocket.
The experiments first had to establish that body heat is sufficient to sustain koji at all. It was, and only then did we test the electronics to find which parts had to be in the final prototype to make the experience educational rather than merely functional. Colour readings and probe temperatures were logged across growth runs with two or three replicates, which is enough to build a device on and not enough to publish.
We drew on the Tamagotchi because it is a format everyone knows and that triggers no adverse reaction, and because it is a tool for practising caretaking. It avoids extreme direct exposure to microbes and instead teaches, gently, what a microbe needs and how to provide it. Sifting through the sensor data we realised the wearer needed a simpler way to know how the koji was doing, so we drew the KojiMoji, an avatar that reacts to the conditions in the chamber and prompts the wearer, a digital guide to fermentation that builds sensory fluency over time. For the promo video we leaned into a nineties aesthetic, a tribute to the Tamagotchi and an argument for a plurality of aesthetic choices in biodesign, which usually defaults to clean and neat.
Co-production with a living thing, practised daily.
The user study had two parts. In an interactive session participants smelled, touched and optionally tasted koji and handled the prototype while we watched their responses. An online survey then asked about comfort, curiosity, knowledge and concerns around fermentation and microbially powered technology.
Synthetic biology shows us that livingness is a key quality in materials, and that life and technology are more deeply connected than the old picture of control admits. The holobiont, a host and all its microbes as one living unit, describes the wearer of a KojiGotchi accurately. What the device demonstrates is small: a daily caretaking ritual with a fungus, and a person who comes away able to read what a living thing needs. That reading skill is what the more-than-human future will run on, and it can be practised now.
The project is a demo-version of a reciprocal relationship, and I keep calling it that. What it managed was to turn a distant, theoretical utopia into an object that asks something of you every day, and to do it in a format that nobody outside the field had to be talked into.
The finals in New York and the Algae Magazine feature put it in front of the biodesign field. It was built for the people outside it, and the user study is early evidence for anyone making living products: how people respond when they smell, touch and wear a living culture is the first question that market will face.
Care is a mindful way of acting and relating, where everyone relies on each other.
From the project glossary · 2025