Noah Ziethen
@nziethen.bsky.social
24 followers 68 following 5 posts
Postdoctoral researcher in theoretical physics, curious about living and active matter.
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Reposted by Noah Ziethen
stefankoestler2025.bsky.social
New preprint 🥳
In our new paper, we show that “Advection selects pattern in multi-stable emulsions of active droplets” — which provides a path toward controlling regular arrangements of droplets. 🧵
📄 arxiv.org/abs/2510.00827
nziethen.bsky.social
🔬 Cells use droplets to organize their interior, sometimes forming liquid bridges between intracellular structures.
While passive bridges attract, we show that activity can make them repel. Cells might use this to control organelle placement & morphology.
nziethen.bsky.social
By combining the fixed bridge radius with a thin-interface approximation, we derived an analytic force expression for a cylindrical active bridge.

✅ It matches the scaling found in simulations—showing that size control is the main driver of the observed effects.
nziethen.bsky.social
Why?
Passive: Stretching increases surface energy, pulling walls together
Active: Chemical reactions maintain fixed bridge radius regardless of wall separation
👉 The bridge doesn't thin but can grow in volume → it is energetically favorable for the walls to move apart, generating repulsion.
nziethen.bsky.social
New preprint 🎉
What began as Frieder Johannsen’s bachelor thesis in the @zwickergroup.bsky.social (which I had the pleasure to supervise) evolved into our latest paper: “Chemically Active Liquid Bridges Generate Repulsive Forces” — unlike passive ones, which attract.
📄 arxiv.org/abs/2509.18777