Noah Ziethen
@nziethen.bsky.social
Postdoctoral researcher in theoretical physics, curious about living and active matter.
Many thanks to Frieder Johannsen and the @zwicker-group!
📄 arxiv.org/abs/2509.18777
📄 arxiv.org/abs/2509.18777
Chemically Active Liquid Bridges Generate Repulsive Forces
Droplets help organize cells by compartmentalizing biomolecules and by mediating mechanical interactions. When bridging two structures, such droplets generate capillary forces, which depend on surface...
arxiv.org
September 29, 2025 at 5:19 PM
Many thanks to Frieder Johannsen and the @zwicker-group!
📄 arxiv.org/abs/2509.18777
📄 arxiv.org/abs/2509.18777
🔬 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.
While passive bridges attract, we show that activity can make them repel. Cells might use this to control organelle placement & morphology.
September 29, 2025 at 5:19 PM
🔬 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.
While passive bridges attract, we show that activity can make them repel. Cells might use this to control organelle placement & morphology.
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.
✅ It matches the scaling found in simulations—showing that size control is the main driver of the observed effects.
September 29, 2025 at 5:18 PM
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.
✅ It matches the scaling found in simulations—showing that size control is the main driver of the observed effects.
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.
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.
September 29, 2025 at 5:17 PM
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.
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.