Clustering of self-propelled particles

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Many experimental realizations of self-propelled particles exhibit a strong tendency to aggregate and form clusters, [1] [2] [3] [4] [5] whose dynamics are much richer than those of passive colloids. These aggregates of particles form for a variety of reasons, from chemical gradients to magnetic and ultrasonic fields. [6] Self-propelled enzyme motors and synthetic nanomotors also exhibit clustering effects in the form of chemotaxis. Chemotaxis is a form of collective motion of biological or non-biological particles toward a fuel source or away from a threat, as observed experimentally in enzyme diffusion [7] [8] [9] and also synthetic chemotaxis [10] [11] [12] or phototaxis. [12] In addition to irreversible schooling, self-propelled particles also display reversible collective motion, such as predator–prey behavior and oscillatory clustering and dispersion. [13] [14] [15] [16] [17]

Contents

Phenomenology

This clustering behavior has been observed for self-propelled Janus particles, either platinum-coated gold particles [1] or carbon-coated silica beads, [2] and for magnetically or ultrasonically powered particles. [5] [6] Clustering has also been observed for colloidal particles composed of either an embedded hematite cube [3] or slowly-diffusing metal ions. [4] [13] [14] [15] [16] Autonomous aggregation has also been observed in anatase TiO2 (titanium dioxide) particles. [18] Clustering also occurs in enzyme molecule diffusion. [7] [8] [9] [19] Recently, enzymes such as hexokinase and alkaline phosphatase were found to aggregate in the presence of their substrates. [20] In all these experiments, the motion of particles takes place on a two-dimensional surface and clustering is seen for area fractions as low as 10%. For such low area fractions, the clusters have a finite mean size [1] while at larger area fractions (30% or higher), a complete phase separation has been reported. [2] The dynamics of the finite-size clusters are very rich, exhibiting either crystalline order or amorphous packing. The finite size of the clusters comes from a balance between attachment of new particles to pre-existing clusters and breakdown of large clusters into smaller ones, which has led to the term "living clusters". [3] [4] [13] [14] [15] [16]

Mechanism for synthetic systems

The precise mechanism leading to the appearance of clusters is not completely elucidated and is a current field of research for many systems. [21] A few different mechanisms have been proposed, which could be at play in different experimental setups.

Self-propelled particles can accumulate in a region of space where they move with a decreased velocity. [22] After accumulation, in regions of high particle density, the particles move more slowly because of steric hindrance. A feedback between these two mechanisms can lead to the so-called motility induced phase separation. [23] This phase separation can, however, be arrested by chemically-mediated inter-particle torques [24] or hydrodynamic interactions, [25] [26] which could explain the formation of finite-size clusters.

Alternatively, clustering and phase-separation could be due to the presence of inter-particle attractive forces, as in equilibrium suspensions. Active forces would then oppose this phase separation by pulling apart the particles in the cluster, [27] [28] following two main processes. First, single particles can exist independently if their propulsion forces are sufficient to escape from the cluster. Secondly, a large cluster can break into smaller pieces due to the build-up of internal stress: as more and more particles enter the cluster, their propulsive forces add up until they break down its cohesion.

Diffusiophoresis is also a commonly cited mechanism for clustering and collective behavior, involving the attraction or repulsion of particles to each other in response to ion gradients. [4] [13] [14] [15] [16] Diffusiophoresis is a process involving the gradients of electrolyte or non-electrolyte concentrations interacting with charged (electrophoretic interactions) or neutral (chemophoretic interactions) particles in solution and with the double layer of any walls or surfaces (electroosmotic interactions). [15] [16]

In experiments, arguments have been put forward in favor of any of the above mechanisms. For carbon-coated silica beads, attractive interactions are seemingly negligible and phase-separation is indeed seen at large densities. [2] For other experimental systems, however, attractive forces often play a larger role. [1] [3] [15] [16]

See also

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References

  1. 1 2 3 4 Theurkauff, I.; Cottin-Bizonne, C.; Palacci, J.; Ybert, C.; Bocquet, L. (26 June 2012). "Dynamic Clustering in Active Colloidal Suspensions with Chemical Signaling". Physical Review Letters. 108 (26): 268303. arXiv: 1202.6264 . Bibcode:2012PhRvL.108z8303T. doi:10.1103/PhysRevLett.108.268303. PMID   23005020. S2CID   4890068.
  2. 1 2 3 4 Buttinoni, Ivo; Bialké, Julian; Kümmel, Felix; Löwen, Hartmut; Bechinger, Clemens; Speck, Thomas (5 June 2013). "Dynamical Clustering and Phase Separation in Suspensions of Self-Propelled Colloidal Particles". Physical Review Letters. 110 (23): 238301. arXiv: 1305.4185 . Bibcode:2013PhRvL.110w8301B. doi:10.1103/PhysRevLett.110.238301. PMID   25167534. S2CID   17127522.
  3. 1 2 3 4 Palacci, Jeremie; Sacanna, Stefano; Steinberg, Asher Preska; Pine, David J.; Chaikin, Paul M. (31 January 2013). "Living Crystals of Light-Activated Colloidal Surfers". Science. 339 (6122): 936–40. Bibcode:2013Sci...339..936P. doi:10.1126/science.1230020. ISSN   0036-8075. PMID   23371555. S2CID   1974474.
  4. 1 2 3 4 Ibele, Michael; Mallouk, Thomas E.; Sen, Ayusman (20 April 2009). "Schooling Behavior of Light-Powered Autonomous Micromotors in Water". Angewandte Chemie. 121 (18): 3358–3362. Bibcode:2009AngCh.121.3358I. doi:10.1002/ange.200804704. ISSN   1521-3757.
  5. 1 2 Kagan, Daniel; Balasubramanian, Shankar; Wang, Joseph (10 January 2011). "Chemically Triggered Swarming of Gold Microparticles". Angewandte Chemie International Edition. 50 (2): 503–506. doi:10.1002/anie.201005078. ISSN   1521-3773. PMID   21140389.
  6. 1 2 Wang, Wei; Castro, Luz Angelica; Hoyos, Mauricio; Mallouk, Thomas E. (24 July 2012). "Autonomous Motion of Metallic Microrods Propelled by Ultrasound". ACS Nano. 6 (7): 6122–6132. doi:10.1021/nn301312z. ISSN   1936-0851. PMID   22631222.
  7. 1 2 Muddana, Hari S.; Sengupta, Samudra; Mallouk, Thomas E.; Sen, Ayusman; Butler, Peter J. (24 February 2010). "Substrate Catalysis Enhances Single-Enzyme Diffusion". Journal of the American Chemical Society. 132 (7): 2110–2111. doi:10.1021/ja908773a. ISSN   0002-7863. PMC   2832858 . PMID   20108965.
  8. 1 2 Sengupta, Samudra; Dey, Krishna K.; Muddana, Hari S.; Tabouillot, Tristan; Ibele, Michael E.; Butler, Peter J.; Sen, Ayusman (30 January 2013). "Enzyme Molecules as Nanomotors". Journal of the American Chemical Society. 135 (4): 1406–1414. doi:10.1021/ja3091615. ISSN   0002-7863. PMID   23308365.
  9. 1 2 Dey, Krishna Kanti; Das, Sambeeta; Poyton, Matthew F.; Sengupta, Samudra; Butler, Peter J.; Cremer, Paul S.; Sen, Ayusman (23 December 2014). "Chemotactic Separation of Enzymes". ACS Nano. 8 (12): 11941–11949. doi: 10.1021/nn504418u . ISSN   1936-0851. PMID   25243599.
  10. ↑ Pavlick, Ryan A.; Sengupta, Samudra; McFadden, Timothy; Zhang, Hua; Sen, Ayusman (26 September 2011). "A Polymerization-Powered Motor". Angewandte Chemie International Edition. 50 (40): 9374–9377. doi:10.1002/anie.201103565. ISSN   1521-3773. PMID   21948434. S2CID   6325323.
  11. ↑ Hong, Yiying; Blackman, Nicole M. K.; Kopp, Nathaniel D.; Sen, Ayusman; Velegol, Darrell (26 October 2007). "Chemotaxis of Nonbiological Colloidal Rods". Physical Review Letters. 99 (17): 178103. Bibcode:2007PhRvL..99q8103H. doi:10.1103/PhysRevLett.99.178103. PMID   17995374.
  12. 1 2 Chaturvedi, Neetu; Hong, Yiying; Sen, Ayusman; Velegol, Darrell (4 May 2010). "Magnetic Enhancement of Phototaxing Catalytic Motors". Langmuir. 26 (9): 6308–6313. doi:10.1021/la904133a. ISSN   0743-7463. PMID   20102166.
  13. 1 2 3 4 Hong, Yiying; Diaz, Misael; Córdova-Figueroa, Ubaldo M.; Sen, Ayusman (25 May 2010). "Light-Driven Titanium-Dioxide-Based Reversible Microfireworks and Micromotor/Micropump Systems". Advanced Functional Materials. 20 (10): 1568–1576. doi:10.1002/adfm.201000063. ISSN   1616-3028. S2CID   51990054.
  14. 1 2 3 4 Ibele, Michael E.; Lammert, Paul E.; Crespi, Vincent H.; Sen, Ayusman (24 August 2010). "Emergent, Collective Oscillations of Self-Mobile Particles and Patterned Surfaces under Redox Conditions". ACS Nano. 4 (8): 4845–4851. doi:10.1021/nn101289p. ISSN   1936-0851. PMID   20666369.
  15. 1 2 3 4 5 6 Duan, Wentao; Liu, Ran; Sen, Ayusman (30 January 2013). "Transition between Collective Behaviors of Micromotors in Response to Different Stimuli". Journal of the American Chemical Society. 135 (4): 1280–1283. doi:10.1021/ja3120357. ISSN   0002-7863. PMID   23301622.
  16. 1 2 3 4 5 6 Altemose, Alicia; Sánchez-Farrán, Maria A.; Duan, Wentao; Schulz, Steve; Borhan, Ali; Crespi, Vincent H.; Sen, Ayusman (2017). "Chemically-Controlled Spatiotemporal Oscillations of Colloidal Assemblies". Angew. Chem. Int. Ed. 56 (27): 7817–7821. doi:10.1002/anie.201703239. PMID   28493638.
  17. ↑ Zhang, Jianhua; Laskar, Abhrajit; Song, Jiaqi; Shklyaev, Oleg E.; Mou, Fangzhi; Guan, Jianguo; Balazs, Anna C.; Sen, Ayusman (10 January 2023). "Light-Powered, Fuel-Free Oscillation, Migration, and Reversible Manipulation of Multiple Cargo Types by Micromotor Swarms". ACS Nano. 17 (1): 251–262. doi:10.1021/acsnano.2c07266. ISSN   1936-0851. PMID   36321936. S2CID   253257444.
  18. ↑ Zhang, Jianhua; Song, Jiaqi; Mou, Fangzhi; Guan, Jianguo; Sen, Ayusman (26 February 2021). "Titania-Based Micro/Nanomotors: Design Principles, Biomimetic Collective Behavior, and Applications". Trends in Chemistry. 3 (5): 387–401. doi: 10.1016/j.trechm.2021.02.001 . ISSN   2589-5974.
  19. ↑ Zhao, Xi; Palacci, Henri; Yadav, Vinita; Spiering, Michelle M.; Gilson, Michael K.; Butler, Peter J.; Hess, Henry; Benkovic, Stephen J.; Sen, Ayusman (18 December 2017). "Substrate-driven chemotactic assembly in an enzyme cascade". Nature Chemistry. 10 (3): 311–317. Bibcode:2018NatCh..10..311Z. doi:10.1038/nchem.2905. ISSN   1755-4330. PMID   29461522.
  20. ↑ Gentile, Kayla; Bhide, Ashlesha; Kauffman, Joshua; Ghosh, Subhadip; Maiti, Subhabrata; Adair, James; Lee, Tae-Hee; Sen, Ayusman (22 September 2021). "Enzyme aggregation and fragmentation induced by catalysis relevant species". Physical Chemistry Chemical Physics. 23 (36): 20709–20717. Bibcode:2021PCCP...2320709G. doi:10.1039/D1CP02966E. ISSN   1463-9084. PMID   34516596. S2CID   237507756.
  21. ↑ Ball, Philip (11 December 2013). "Focus: Particle Clustering Phenomena Inspire Multiple Explanations". Physics. 6: 134. doi:10.1103/physics.6.134 . Retrieved 22 September 2015.
  22. ↑ Schnitzer, Mark J. (1 October 1993). "Theory of continuum random walks and application to chemotaxis". Physical Review E. 48 (4): 2553–2568. Bibcode:1993PhRvE..48.2553S. doi:10.1103/PhysRevE.48.2553. PMID   9960890.
  23. ↑ Cates, Michael E.; Tailleur, Julien (1 January 2015). "Motility-Induced Phase Separation". Annual Review of Condensed Matter Physics. 6 (1): 219–244. arXiv: 1406.3533 . Bibcode:2015ARCMP...6..219C. doi:10.1146/annurev-conmatphys-031214-014710. S2CID   15672131.
  24. ↑ Pohl, Oliver; Stark, Holger (10 June 2014). "Dynamic Clustering and Chemotactic Collapse of Self-Phoretic Active Particles". Physical Review Letters. 112 (23): 238303. arXiv: 1403.4063 . Bibcode:2014PhRvL.112w8303P. doi:10.1103/PhysRevLett.112.238303. PMID   24972234. S2CID   15305058.
  25. ↑ Matas-Navarro, Ricard; Golestanian, Ramin; Liverpool, Tanniemola B.; Fielding, Suzanne M. (18 September 2014). "Hydrodynamic suppression of phase separation in active suspensions". Physical Review E. 90 (3): 032304. arXiv: 1210.5464 . Bibcode:2014PhRvE..90c2304M. doi:10.1103/PhysRevE.90.032304. PMID   25314443. S2CID   34233710.
  26. ↑ Zöttl, Andreas; Stark, Holger (18 March 2014). "Hydrodynamics Determines Collective Motion and Phase Behavior of Active Colloids in Quasi-Two-Dimensional Confinement". Physical Review Letters. 112 (11): 118101. arXiv: 1309.4352 . Bibcode:2014PhRvL.112k8101Z. doi:10.1103/PhysRevLett.112.118101. PMID   24702421. S2CID   12399192.
  27. ↑ Redner, Gabriel S.; Baskaran, Aparna; Hagan, Michael F. (26 July 2013). "Reentrant phase behavior in active colloids with attraction". Physical Review E. 88 (1): 012305. arXiv: 1303.3195 . Bibcode:2013PhRvE..88a2305R. doi:10.1103/PhysRevE.88.012305. PMID   23944461. S2CID   6919624.
  28. ↑ Mognetti, B. M.; Šarić, A.; Angioletti-Uberti, S.; Cacciuto, A.; Valeriani, C.; Frenkel, D. (11 December 2013). "Living Clusters and Crystals from Low-Density Suspensions of Active Colloids". Physical Review Letters. 111 (24): 245702. arXiv: 1311.4681 . Bibcode:2013PhRvL.111x5702M. doi:10.1103/PhysRevLett.111.245702. PMID   24483677. S2CID   46111375.
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