Life Finds Its Way: the Engineering Miracle of Centric Diatom
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- 7 min read
When I was visiting Barcelona and saw the windows of Casa Batlló designed by Antoni Gaudí, I found myself thinking: don’t they look like centric diatom?
Gaudí himself left almost no official explanation of Casa Batlló. What we do know is that the building as a whole was inspired by the ocean. He lived from 1852 to 1926, and in the late 19th to early 20th century, diatoms were once a popular subject of microscopic photography, so popular that they were even displayed at social gatherings. Around the same time, the German zoologist Ernst Haeckel published Art Forms in Nature, which included detailed plates of diatoms and influenced the aesthetics of many Art Nouveau creators, including Gaudí.
So perhaps those windows in the living room of Casa Batlló are not entirely unrelated to diatoms after all.
These geometrically striking structures we see under the microscope come from the diatom’s silica shell, its frustule. This is what fascinates engineers the most: using nothing more than biochemical processes, diatoms fabricate highly complex, multifunctional nanostructures.
Their shells are not only beautiful; their strength approaches the theoretical limits of strength-to-density ratios found in natural materials.
So why are diatom shells so complex and diverse? How can they be both light and strong? And what can human engineers learn from them?
Any species that has survived to the present with such diversity is, in a sense, an expert in multi objective optimization. To understand diatoms, we can ask a simple question: what does a single algal cell floating in seawater need to optimize in order to survive?
Avoid being eaten
Manage energy efficiently
Capture sufficient light
Diatoms’ primary defense strategy is to build a silica shell, one that is strong enough to withstand predators. In the ocean, their main predators are copepods with sharp feeding teeth. These predators can apply static and impact loads when biting, and may also subject the diatom to repeated mechanical actions, almost like a tiny jackhammer, introducing vibrational loads that can fracture the shell.
So diatoms are engaged in an arm race with copepod.
At the same time, they must conserve energy. The resources used to build the shell should be minimized, while nutrient uptake efficiency should be maximized. The shell cannot be too thick or heavy, otherwise the cell will sink too quickly and lose access to light. Ideally, the shell should even help optimize how light reaches the cell.
How do you build a shell that is strong, light, and optically functional at the same time? This is essentially a topology optimization problem.
Diatoms have spent around 200 million years evolving into tens of thousands of species, each offering its own solution. The result is an astonishing diversity of geometric forms.
This is their kind of engineering mindset: solving real-world constraints creatively under limited resources.
For example, the shell of many centric diatoms exhibits a sandwich structure.
The outermost layer is Cribrum, a sieve-like plate with nanoscale pores. Because its feature size is comparable to the wavelength of light, it does not simply allow light to pass through. Instead, it scatters and diffracts incoming light, increasing the optical path length and redistributing light in ways that enhance wavelengths more suitable for photosynthesis. It effectively redirects light that would otherwise be lost, improving light capture efficiency in real aquatic environments. It may also attenuate harmful ultraviolet radiation, and potentially shift part of it into wavelengths usable for photosynthesis.
The middle layer consists of honeycomb-like chambers called Areola.
If we take a vertical cross-section of a centric diatom, the walls of these chambers, together with the top and bottom layers, form a structure reminiscent of an I-beam. When resources are limited, the most effective way to increase strength is not to add more material in one structural unit, but to place it strategically. One key measure of strength is stiffness, the resistance to deformation. Engineers discovered that distributing material away from the neutral axis maximizes bending stiffness, leading to the invention of the I-beam. Interestingly, diatoms converged on a similar solution.
What about the horizontal cross-section?
Some diatoms exhibit hexagonal patterns. Why hexagons? As early as 36 BCE, the Roman scholar Marcus Terentius Varro proposed what is now known as the honeycomb conjecture, proven in 1999: regular hexagons partition a plane into equal areas with minimal total perimeter. Under physical constraints, diatoms naturally form similarly sized units, and hexagonal tilings correspond to configurations that minimize boundary length for equal area divisions. Other diatoms exhibit irregular polygons with a gradient in size, denser near the edges and sparser toward the center.
Both structures help distribute stress. Hexagonal networks spread stress across the entire structure, while gradient structures act as a stress management strategy. When a predator bites down, the outer regions bear higher loads. By increasing structural density in these regions, diatoms enhance local stiffness and distribute forces across more microstructures, reducing peak stress.
The innermost layer of the sandwich contains reinforced openings known as Foramen.
Computational fluid dynamics simulations show that reinforcement rings around these openings alter flow patterns. Without reinforcement, fluid tends to accumulate near the edges. With reinforcement, recirculation occurs, allowing fluid that initially fails to enter the pore to return in a second pulse. Researchers, therefore, hypothesize that this structure may improve nutrient capture and retention in environments where nutrient distribution is heterogeneous. When fluid flows outward, these structures increase the tortuosity of flow paths, reduce flow velocity, and promote a more uniform internal pressure distribution.
In addition to resisting static and impact loads, diatoms may also use structural features to cope with vibrational loads.
If the frequency of periodic disturbances generated by predators approaches one of the shell’s natural frequencies, resonance may occur, leading to amplified deformation and an increased risk of structural failure. The stability of a diatom shell under vibration depends both on whether its natural frequencies align with external excitation and on the stiffness that determines its deformation amplitude. Higher stiffness generally leads to higher natural frequencies and smaller deformation, thereby reducing the likelihood of damaging resonance. For example, the bulging structure of Actinoptychus sp. may increase stiffness and disrupt continuous vibration modes, making it harder for large amplitude resonance to develop.
The most fascinating aspect of diatom engineering lies in the fact that it is not designed, but emerges. As single celled organisms, diatoms do not possess the capacity to compute moments of inertia or optimize topological functions. They follow what Richard Dawkins described as the logic of the blind watchmaker.
Over hundreds of millions of years, evolution continuously filters the rules governing silica deposition. Structures that fail to develop efficient load bearing pathways, or whose natural frequencies coincide with predators’ disturbances, are more likely to break and disappear under external pressures. Through this process of blind selection, highly effective engineering solutions are gradually embedded into material form.
Perhaps life is not searching for a destined answer, but instead exploring through continuous trial and error, retaining only what happens to work. What remains is not an intentionally derived optimum, but one repeatedly validated by time.
Diatoms arrive at their solutions through unconscious intelligence; today, human engineers are attempting to translate these solutions into design rules. Rather than imitating specific shapes as in the era of Gaudi, engineers input material properties, boundary conditions, loading scenarios, performance objectives, and geometric design variables into parametric models, optimization algorithms, and even generative AI systems. These systems simulate a selection process similar to that of diatoms, automatically generating new material architectures. Materials inspired by diatoms may one day combine the organic aesthetics seen in Gaudí’s work with the logic of algorithms, redefining the boundaries of human manufacturing.
I hope that one day I can sit by the sea with a microscope, observe diatoms of different shapes, and witness the ingenuity of nature firsthand. If this sparked your curiosity as well, feel free to check out the portable microscope project I am working on: eurekamicroscope.com