Seed-Seeded Wrinkles and an Everlasting Avalanche Win Gallery Contest
The APS Division of Soft Matter announced the winners of the Gallery of Soft Matter 2026 contest at the APS Global Physics Summit, which took place last week in Denver. Here is a rundown of the two posters and the video that were selected.
Expanding Basil Seeds
Watching online short-form videos is a notorious time sink, but for doctoral student Juyeong Hong and colleagues at Seoul National University in South Korea, the pastime turned out to be surprisingly productive. In a video about a popular basil-seed drink, Hong noticed that the seeds swelled in size when placed in water, creating self-organized wrinkling patterns on the surface. That video served as the motivation for the team’s winning poster presentation.
The patterns of wrinkles that Hong saw in the video emerge owing to a buckling instability that relieves compressive stresses generated by the swelling seeds. Hong and colleagues studied this phenomenon using not only basil seeds but chia seeds and granules of superabsorbent polymer. They also varied the density of the liquid on which the seeds and granules floated and the proportion of the surface that was covered by the particles. When the particles had expanded to their limit, the researchers added blue dye to highlight the contours of the resulting pattern.
In their initial experiments, they explored the link between the wavelength of the wrinkle pattern and the swelling ratio of the floating particles. In future research, they intend to include the effects of the density and surface tension of the liquid and the packing density of the floating particles. Hong says that the work could offer a way to study biological systems in which the controlling variables are hard to manipulate, such as developing tissues or bacterial biofilms.
Self-Assembling Nanostars
A self-organization process is also the subject of the other winning poster presentation; in this case, the spontaneous assembly of four-armed DNA “nanostars” into a complex network. Graduate student Ian Lillie and colleagues at the University of San Diego aim to use these nanostars as the basis for an autonomous material-fabrication process. “We are engineering systems that don’t just exist but ‘behave’—restructuring themselves from molecular building blocks into programmed architectures,” says project leader Rae Robertson-Anderson.
In the featured work, the team exploited this self-assembly process in a solution containing DNA nanostars and starch granules. The ends of the DNA arms form weak, reversible bonds with the starch granules. The creation and destruction of these bonds cause the configuration of nanostars to evolve over time. Eventually, the nanostars engulf the starch granules and, by crosslinking their arms, form a porous network.
The precise configuration adopted by the DNA nanostars is influenced by the nature of their interactions with the starch granules. Modifying that interaction provides a way to tune the nanostars’ behavior, potentially leading to applications such as self-growing synthetic tissues, adaptive soft robotics, and infrastructure that can heal or restructure its own anatomy in response to environmental cues, Robertson-Anderson says.
An Endless Avalanche
The winning video presentation was created by doctoral student Rylan Hodgson and colleagues at the University of Colorado Boulder. The researchers’ video showcases a unique view of the dynamics of granular flows. “Events such as avalanches are short-lived, and taking long-term experimental data is very difficult,” Hodgson says. Yet such long-term measurements are necessary to accumulate useful statistical information about these flows.
To solve this problem, Hodgson and colleagues simulate a granular flow without end. They rotate a drum that is partially filled with clear plastic disks. These disks are photoelastic, meaning that circularly polarized light transmitted through a disk has its degree of polarization changed depending on stresses present within the material. Viewing the drum through a circular-polarization filter reveals how these stresses form force chains and networks, which appear briefly as lightning-like flashes of light. Such interparticle interactions are impossible to observe in a real-world granular flow.
Hodgson says that, although the rotating-drum setup captures the physics underlying granular flows, the extent to which it reproduces their statistical properties is a key outstanding question. In future work, Hodgson hopes to build a larger version of the experiment, which should mimic natural flows more accurately.
–Marric Stephens
Marric Stephens is a Corresponding Editor for Physics Magazine based in Bristol, UK