Locating the carrier: what a living material asks of you

Dear {{first_name | reader}},

There's no right way to start a biodesign project. Some people begin with a material they've fallen for, some with a place or a community they want to work alongside, some with a question, a technique, or an ecological worry they can't put down. Those are all good doors, and none is more right than another.

So take this week's letter as one option among many, not a method you have to adopt. It's a way of thinking I reach for in two moments: 1) when a living material has been described to me with a promise I find slippery, and 2) when I'm stuck at the very start, holding something alive and not yet sure what I'm actually working with.

When it does help, it's usually because of a single move. Before you design with a living material, it's worth finding out what actually carries the property that drew you to it.

Name what you're holding and you can see where the real work sits, and how the promise is most likely to fail: chasing a purer molecule when the property is really a geometry, say, or promising a shippable material when it only exists while the organism is alive.

Here are the four kinds of thing a property can live in. Try them on, and keep them only if they earn a place in how you work.

Whatever a biological or living material is sold on, some colour, some strength, a way it seems to sense or heal, that property depends on one of four things.

I've started calling that thing its biodesign carrier: the level of organisation, or the relationship, the property primarily depends on. Take it away and the property goes with it.

These are not sealed compartments: A property can lean on more than one at once, so the useful question is which one is indispensable: which level has to stay intact for the property you care about to survive. That one is the primary carrier; the rest are supporting conditions.

Naming the property is yours to do: "the angle-shifting blue" rather than "colour", "re-seals a cut within a day" rather than "it heals". That takes looking closely, over days and in different light, and no AI tool can do it for you.

Working out which of the four carries it is mostly something the material itself will tell you, if you test it and give it time. I'll come to how, and to the one narrow place an AI tool helps. What the four add is the part nothing else gives you: knowing what each one then asks of you.

One example runs through the rest of this letter. The marble berry, a small forest fruit, holds an intense blue that comes from no blue pigment at all. The colour is carried by an arrangement of ordinary cellulose, stacked in fine helical layers in the outer cell walls of the fruit.

So it belongs to the second kind below, and the work is to preserve that geometry, not to chase a blue that was never there. I'm writing a full read of it now, taken all the way down, and I'll share it at the end of this week, when the members' library opens (Vignolini et al., 2012).

Each one below says the same four things in plain terms: what actually carries the property, how you can tell you're looking at it, what it then asks of you to hold on to it, and the way it most often falls apart.

Here the property lives in a molecule: a dye, a pigment, a compound, a protein. You can tell because you can take the molecule out and it still works, even dissolved in a drop of liquid.

So you keep it, and the work is chemistry: making enough of it, pure enough, and stable once it's out of the organism. It falls apart when the molecule breaks down, when there's too little to matter, or when it stops working the moment it leaves the living thing.

Here the property lives in an arrangement: a spacing, a geometry, the way something is packed. You can tell because it survives being taken out, but not being ground up or reshaped. Wreck the arrangement and the property goes, even though nothing was removed.

So you preserve it, and the work is fabrication: making that geometry again and holding it through drying, handling, and scaling up. It falls apart when the arrangement collapses as the material dries, is handled, or is made bigger. The marble berry's blue lives here.

Here the property lives in something the organism is actively doing while it's alive: sensing, repairing, growing, feeding. You can tell because it stops when that activity stops.

So you tend it, and the work is keeping the organism alive, fed, and in the right conditions, at the size and for the length of time your design needs. It falls apart when you can't keep it alive long enough or large enough, and the property dies with the organism.

This one is easy to oversell, because the activity is often shown briefly, at lab scale, and then described as if it will stay dependable in use.

Here the property depends on an interaction between organisms, usually together with the conditions around them, and no single partner has it alone. You can tell because it weakens or goes when you separate the partners, or when the conditions that hold their interaction are disrupted.

A lichen greens bare rock through a fungus living with one or more photosynthetic partners, usually an alga or a cyanobacterium, inside a wider microbial community.

So you tend the relationship, caring for the partners together and the conditions that sustain them, rather than putting one of them to work. It falls apart when a partner drops out or the conditions shift, and it's easy to misread as a portable material when the property really depends on keeping a whole relationship alive (Karana, Barati and Giaccardi, 2020; Groutars, Kim and Karana, 2024).

This is a well-grounded instrument, not a new theory. It carries two established ideas into the moment a promise reaches you.

The first is the materials idea that a property lives in a substance or in a structure, and that a structural property is set by how a thing is made, not only what it is made of (National Research Council, 1989; Olson, 1997).

Many biological material properties arise from hierarchical arrangements across scales, not from chemical composition alone (Fratzl and Weinkamer, 2007; Meyers et al., 2008; Vincent, 2012), which is why the marble berry's blue is a stack of ordinary cellulose and not a dye.

The framework keeps that substance-versus-structure distinction and adds the two dimensions a materials paradigm built for inert matter leaves out: an ongoing living process, and a relationship between organisms. With them comes the separation test, which asks whether a property survives once it is taken out of the living thing, or the relationship, that carries it.

The second is the biological view that many organisms live and work through lasting associations with other organisms (Sagan, 1967; Zilber-Rosenberg and Rosenberg, 2008; Gilbert, Sapp and Tauber, 2012), so some properties we can see arise from the interaction between partners rather than from any one of them alone (Anderson, 1972).

Organisms also build, and then depend on, the places they live in (Odling-Smee, Laland and Feldman, 2003): they do not just occupy an environment, they change it and can come to rely on the conditions they helped make.

Together these ideas support the relational category, and the idea that a relationship between organisms, held in its conditions, can be the real carrier.

I want to be careful here, because this is the part that matters most. Which of the four you're in is, at heart, a physical question, and the material will answer it more honestly than any description, if you let it.

Does the colour survive once a piece has dried? Compare an already-detached sample before and after, under the same light. Does it survive the structure being disturbed? Disturb a small sacrificial sample and set it beside an intact one. Does the repair depend on the organism still working? Change one condition at a time in a culture you can keep safely, and keep a control.

For a relationship, watch how the property shifts as conditions vary in the wild, or lean on published experiments, rather than pulling a lichen off its rock yourself.

These are diagnostic probes, not proofs: use a control, a safe or sacrificial sample, and the least destructive test that can answer the question. Run them on a bench or on a slow walk in a wood, and the watching is the whole education.

It is also how you come to care about the thing, which nothing can hand you and no shortcut can fake. Time spent with a living material, letting it stay a bit strange, is not a delay before the real work. It is the work.

So where does an AI tool come in? In one narrow place, and only after you've looked. When you want to know what is doing the work underneath, the specific molecule, the exact structure, the biology can sit behind a wall of papers you may not have time to climb. An AI tool (one of the chatbots you already use) can hand you a way in fast.

Use it to suggest search terms, name the candidate mechanisms, and point you at possible papers. Then open those papers and check them yourself: the title, the authors, that the paper is real, and that the passage really says what you were told. A fluent answer is not a proven one, and a fluent model will invent a convincing reference, so the wobble is worth catching.

The AI tool is a door into the literature, not the evidence itself. It's standing in for a library card, not for the bench, and not for your own judgement.

And keep the last question for yourself. An AI model might help you find evidence about the cost, but it cannot settle it for you: what does this property cost the organism or community from which it comes? That one you earn only by paying attention, over time, to the living thing in front of you.

That full read of the marble berry, how the colour comes to sit in the structure, the cell-wall growth that lays down those layers, and every source you can open yourself, arrives at the end of this week, with the launch of the members' library. If you are new here, the free Biodesign Promise Worksheet is the place to start, for taking a promise apart in the first place.

That is what From the Molecule Up is for. It builds the thin layer between a living-material word and the thing that actually does the work, one piece per issue, in the open, before it is a book.

Before you go, one favour. If a "living", "self-healing", or "grown" promise has stayed with you, from a product page, a degree show, or a studio brief, reply and tell me. I will read the sharpest of them through these four in a future issue.

Until next time,

Raphael

P.S. For those of you teaching: this runs better with a real sample than a screen. Give students a material they can handle, an afternoon, and one instruction: name the property, then test it.

Pick one safe test that fits the material, comparing it before and after drying, disturbing a sacrificial piece against an intact control, or changing a single growth condition while keeping one culture untouched, and watch what survives.

Only when they're stuck on the biology underneath should an AI tool come out, and even then as something to check, not to trust. They land on keep it, preserve it, tend it, or tend the relationship, with their own hands as the evidence.

Anderson, P. W. (1972). More is different. Science, 177(4047), 393–396.

Fratzl, P., & Weinkamer, R. (2007). Nature's hierarchical materials. Progress in Materials Science, 52(8), 1263–1334.

Gilbert, S. F., Sapp, J., & Tauber, A. I. (2012). A symbiotic view of life: We have never been individuals. The Quarterly Review of Biology, 87(4), 325–341.

Groutars, E. G., Kim, R., & Karana, E. (2024). Designing living artefacts for multispecies interactions: An ecological approach. International Journal of Design, 18(2), 59–78.

Karana, E., Barati, B., & Giaccardi, E. (2020). Living artefacts: Conceptualizing livingness as a material quality in everyday artefacts. International Journal of Design, 14(3), 37–53.

Meyers, M. A., Chen, P.-Y., Lin, A. Y.-M., & Seki, Y. (2008). Biological materials: Structure and mechanical properties. Progress in Materials Science, 53(1), 1–206.

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Odling-Smee, F. J., Laland, K. N., & Feldman, M. W. (2003). Niche Construction: The Neglected Process in Evolution. Princeton University Press.

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Sagan, L. [Margulis, L.] (1967). On the origin of mitosing cells. Journal of Theoretical Biology, 14(3), 255–274.

Vignolini, S., Rudall, P. J., Rowland, A. V., Reed, A., Moyroud, E., Faden, R. B., Baumberg, J. J., Glover, B. J., & Steiner, U. (2012). Pointillist structural color in Pollia fruit. Proceedings of the National Academy of Sciences, 109(39), 15712–15715.

Vincent, J. F. V. (2012). Structural Biomaterials (3rd ed.). Princeton University Press.

Zilber-Rosenberg, I., & Rosenberg, E. (2008). Role of microorganisms in the evolution of animals and plants: The hologenome theory of evolution. FEMS Microbiology Reviews, 32(5), 723–735.