title: Bacterial ratchet motors.
abstract: Self-propelling bacteria are a nanotechnology dream. These unicellular organisms are not just capable of living and reproducing, but they can swim very efficiently, sense the environment, and look for food, all packaged in a body measuring a few microns. Before such perfect machines can be artificially assembled, researchers are beginning to explore new ways to harness bacteria as propelling units for microdevices. Proposed strategies require the careful task of aligning and binding bacterial cells on synthetic surfaces in order to have them work cooperatively. Here we show that asymmetric environments can produce a spontaneous and unidirectional rotation of nanofabricated objects immersed in an active bacterial bath. The propulsion mechanism is provided by the self-assembly of motile Escherichia coli cells along the rotor boundaries. Our results highlight the technological implications of active matter's ability to overcome the restrictions imposed by the second law of thermodynamics on equilibrium passive fluids.
authors.affiliation: Consiglio Nazionale delle Ricerche-Istituto per i Processi Chimico-Fisici, c/o Università di Roma Sapienza, I-00185, Rome, Italy. roberto.dileonardo@phys.uniroma1.it
authors.forename: R
authors.initials: R
authors.lastname: Di Leonardo
authors.forename: L
authors.initials: L
authors.lastname: Angelani
authors.forename: D
authors.initials: D
authors.lastname: Dell'arciprete
authors.forename: G
authors.initials: G
authors.lastname: Ruocco
authors.forename: V
authors.initials: V
authors.lastname: Iebba
authors.forename: S
authors.initials: S
authors.lastname: Schippa
authors.forename: M P
authors.initials: MP
authors.lastname: Conte
authors.forename: F
authors.initials: F
authors.lastname: Mecarini
authors.forename: F
authors.initials: F
authors.lastname: De Angelis
authors.forename: E
authors.initials: E
authors.lastname: Di Fabrizio
mesh_terms: D004926:Escherichia coli / Q000502:physiology* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009068:Movement; D013816:Thermodynamics
references.citation: Proc Natl Acad Sci U S A. 2005 Aug 23;102(34):11963-7
references.pmid: 16103369
references.citation: Phys Rev Lett. 1995 Aug 7;75(6):1226-1229
references.pmid: 10060237
references.citation: Nature. 1973 Oct 19;245(5425):380-2
references.pmid: 4593496
references.citation: Phys Rev Lett. 2000 Mar 27;84(13):3017-20
references.pmid: 11019000
references.citation: Biochem Biophys Res Commun. 2005 May 27;331(1):318-24
references.pmid: 15845395
references.citation: Annu Rev Biochem. 2003;72:19-54
references.pmid: 12500982
references.citation: Phys Rev Lett. 2005 Nov 11;95(20):204501
references.pmid: 16384062
references.citation: Phys Rev Lett. 2002 Jul 29;89(5):058101
references.pmid: 12144468
references.citation: Phys Rev Lett. 2009 Jan 30;102(4):048104
references.pmid: 19257480
references.citation: Science. 1997 May 9;276(5314):917-22
references.pmid: 9139648
references.citation: Biophys J. 2004 Mar;86(3):1863-70
references.pmid: 14990512
references.citation: J Gen Microbiol. 1967 Feb;46(2):175-84
references.pmid: 4961758
references.citation: Nature. 2005 Jun 30;435(7046):1271-4
references.pmid: 15988531
references.citation: Proc Natl Acad Sci U S A. 2006 Sep 12;103(37):13618-23
references.pmid: 16950878