Topic
Active matter research, explained
13 open-access active matter studies, each with a flashcard deck and a quiz.
- Can light alone drive and steer tiny swimming particles?
Half-gold microbeads swim when heated by a wide laser and can be turned by a focused laser, letting a computer steer them to a target without chemical fuel.
- Why do swimming bacteria drift sideways in a flowing channel?
The corkscrew shape of E. coli's flagella makes the bacteria drift across the flow at a speed that rises linearly with shear at first and then levels off well below their swimming speed.
- Can simple buzzing robots be programmed to clump like a material?
Mindless vibrating robots with magnets switch from scattered to clumped at a threshold attraction, just as a statistical-physics lattice model predicts.
- Can magnetic beads stack themselves upward against gravity?
A carefully shaped oscillating magnetic field makes tiny magnetic beads build and maintain tall towers against gravity that can change shape, move and cooperate to cross obstacles.
- Why do swimming micro-disks clump into slow pairs?
Self-propelled disk-shaped particles grab each other through the flows they create, forming slow pairs that trap more particles and freeze the crowd's motion.
- Can a particle-based fluid simulation capture active nematic turbulence?
A new mesoscale simulation method for active liquid crystals reproduces active turbulence with the length and speed scalings theory predicts, while also showing the large density fluctuations seen in active particle systems.
- Why do moving protein filaments switch from swirls to aligned order?
As treadmilling FtsZ filaments get more crowded they straighten out, so their collective pattern changes from rotating chiral rings to a nematic, liquid-crystal-like order, and a flexible-filament model reproduces this.
- Can an algorithm find the equations behind active nematic flows?
A physics-constrained regression algorithm, fed with movies of motor-driven microtubules, recovered simple flow equations in which active stress balances viscous friction with no elastic term, differing from standard models.
- Do the tiny hairs on algal flagella help the cell swim?
Removing the fine hairs from Chlamydomonas flagella does not change how fast the cells swim, how their flagella beat, or how much fluid they push.
- How do field-powered colloidal dumbbells and triangles move?
Changing the shape of self-rolling colloids from spheres to dumbbells or triangles produces qualitatively new motions: spinning, orbiting, spinning bound pairs and flipping.
- How do motors make microtubule bundles stretch?
Adding a crowding agent packs microtubules more tightly and changes how the filaments move inside a bundle, even though the bundle as a whole keeps stretching.
- Can frustrated self-propelled particles become hyperuniform?
In simulations, self-propelled particles whose alignment rule is frustrated can settle into a disordered yet hyperuniform state, even though no single orientation group is hyperuniform on its own.
- Can swimming bacteria spin a perfectly symmetric disc?
A bacterium trapped under a symmetric disc makes it rotate because its body and its tail spin in opposite directions, even without pushing on any wall.