From Clarkia to Escherichia and Janus: the physics of natural and synthetic active colloids

摘要: An active colloid is a suspension of particles that transduce free energy from their environment and use the to engage in intrinsically non-equilibrium activities such as growth, replication self-propelled motility. obvious example colloids bacteria Escherichia coli, physical dimensions being almost invariably colloidal range. Synthetic have also become available recently, two-faced, or Janus, propelled by differential chemical reactions on surfaces driving self-phoretic motion. In these lectures, I give pedagogical introduction physics single-particle collective properties colloids, focussing self propulsion. will compare contrast phenomena suspensions `swimmers' with behaviour passive particles, where only Brownian motion (discovered Robert Brown granules pollen wild flower {\it Clarkia pulchella}) relevant. pay particular attention issues pertain performing experiments using particle suspensions, how characterise suspension's swimming speed distribution, include an appendix guide physicists wanting start culturing motile bacteria.