Instability as a design tool for patterning

From dendritic snowflakes to river networks, nature ‘fabricate’ complex structures using instabilities characterized by self-amplified growth of small perturbations. The practical challenge is to steer such unstable growth into useful forms. We developed strategies to use viscous fingering, an interfacial instability when a less viscous fluid displaces a more viscous one in a confined environment, as a controllable writer of structure in anisotropic media. Using Hele-Shaw cells with engraved lattices (impose environmental anisotropy) and nematic lyotropic chromonic liquid crystals (supply intrinsic material anisotropy), we switched growth morphology from dense branches to stable dendrites. We then derived scaling rules for both mechanisms: with environmental anisotropy, the transition is governed by viscosity ratio and the degree of anisotropy in permeability; with intrinsic anisotropy, it is set by a single dimensionless ratio comparing flow‑induced viscous torque to molecular elastic relaxation. These results guide pattern fabrication and motivate applications in analogous systems with gradient-driven interfacial dynamics, such as directional solidification or template-assisted electrodeposition.

Flow-elastic coupling writes microstructures

In nematic liquid crystals, flow distorts director field against elastic restoring torques, producing microstructures that control transport and optical properties. Nematic lyotropic chromonic liquid crystals (LCLCs) are water‑based and biocompatible, with peculiar larger material anisotropy than classical thermotropic LCs. Their flow properties were barely explored, limiting the applications for biosensor and drug delivery. Using polarization‑resolved microscopy and custom microfluidics, I systematically mapped flow-induced structures in pressure‑driven LCLCs flow. I revealed twist‑type defects unique to nematic LCLCs and showed that their size is set by a tunable nucleation-annihilation balance. As flow velocity decreases, a periodic double‑twist structure emerges. This is a chiral structure assembled from achiral LCLC building blocks, highlighting a striking flow‑induced mirror symmetry breaking. These findings provide quantitative guidance for molecular assembly under flow.

Life in a freezing, porous world

Sea ice is a porous structure filled with brine channels. Ice diatoms dominate sea-ice algal communities and are the primary producers prior to the spring phytoplankton bloom. However, whether diatoms can actively navigate the ice matrix was unknown. Using a custom sub-zero temperature microscope during a 45-day Arctic expedition and together with laboratory assays, I show that ice diatoms uniquely glide across sea ice at subzero temperatures, whereas temperate species lose motility on contact. I adapt traction‑force microscopy to map single-cell forces and build a thermo‑hydrodynamic model that explains how internal myosin motors and external viscosity jointly sustain motion in extreme cold. These results transform static ice into a dynamic landscape, setting the mechanical basis for colonization and motion in freezing environment.

Polar diatoms affect ice nucleation and growth

By developing a temperature-controlled microfluidic system reaching -40°C with 0.1-degree precision, I reveal intriguing interactions between forming ice crystals and live diatoms, showing changes in crystal growth and ice frontier’s complexity. These findings show the critical role of polar diatoms in ice nucleation. Our work spotlights the complex interplay between ice crystal formation and live cells.

Genomic and transcriptomic basis of ice diatoms’ motility

In collaboration with Dr. Zev Bryant’s lab

How do diatoms maintain high-performance motility within the freezing constraints of sea ice? Working with graduate student Hope T. Leng, we are dissecting the genetic architecture of Navicula sp. to answer this question. Our specific focus lies on the intersection of the diatom motility engine and physical ice-cell interactions. We have performed DNA sequencing to identify marker genes responsible for cryo-adaptation. The current phase of the project involves subjecting cultures to a multidimensional environmental matrix, modulating temperature, light intensity, and nutrient availability, to observe how environmental stress controls RNA expression. Our ultimate goal is to bridge the gap between genomic potential and phenotypic expression, linking molecular strategies to the evolutionary success of microbes in extreme environments.

Photo-regulated buoyancy and vertical migration in chain diatoms

Diatoms are photosynthetic unicellular algae encased in siliceous shells and responsible for approximately 20% of global carbon fixation. Their ability to regulate vertical position within the water column is a critical, yet understudied, component of the ocean biological carbon pump. In this study, I designed a controlled irradiance experiment to decouple passive sedimentation from active buoyancy regulation. Preliminary results reveal a distinct behavioral switch: chain-forming diatoms exhibit passive sinking kinetics in darkness but undergo a rapid, light-induced ascent. This experiment establishes a basis for dissecting the vertical migration and quantifying the mechanics of carbon export fluxes in marine ecosystems.

Active nematics in ecosystems

On intertidal mudflats, the collective state of diatoms governs erosion thresholds, advective exchange, and the spatial patterning of primary production. Across tens of meter scales in the field of intertidal mudflats, I discover that dense mudflat diatom communities self-organize into an ecosystem‑scale active nematic phase. Within these carpets, self‑propagating trigger waves arise: cells abruptly accelerate and glide along their common alignment direction, enabling rapid, directional seeding. The mucilage (slime) they secrete onto the substrate imprints environmental memory, allowing rapid restoration of the nematic pattern after a trigger wave. Using micro‑injection, I can elicit waves on demand; with micropatterns, I align the nematics and show that weak physical cues can route biomass flow. This work reveals a dynamical mechanism for fast reorganization on coastal surfaces and establishes quantitative readouts (alignment order, colonization bias, environmental memory) for probing living active matter and active construction.

Active foam networks: Motility-driven topological remodeling

This project investigates the dynamic coupling between active matter and environmental topology within a soft matter system. By introducing a driven active fluid phase into a foam network, I explored how internal active stresses can drive macroscopic structural reorganization in a topologically constrained environment. The core of this research focuses on the mechanics of T1 topological transitions, the fundamental neighbor-swapping events that govern foam plasticity. Through experimental analysis, I derived a scaling law that quantitatively links the motility of the active phase to the rate and nature of these topological rearrangements. This work establishes a framework for understanding how localized energy input can be harnessed to modify global environmental topology, offering new insights into non-equilibrium statistical mechanics and material self-organization.