Active Matter is a rapidly expanding field that investigates the collective properties of materials composed of internally driven objects. The field first rose to prominence with the Vicsek model, which approximates the collective motion of swarms of birds or schools of fish, using point particles. We extend its study to systems at high density, where the interplay between driving, volume exclusion and alignment leads to new classes of dynamical patterns, including phase separation (top, from ), active jammed and active glassy states. Dense active matter systems are prevalent in developmental biology, for example during gastrulation or in the corneal epithelium.
Left: Stress is a boundary term in the shaded region of a frictionless granular packing (from ).Right: Detail of a low-energy normal mode of a frictional granular packing; sliding contacts are in red (from ).
The granular jamming transition is an out-of-equilibrium phase transition characterized by the loss of mechanical rigidity below a certain level of connectivity, and associated anomalous elastic properties. I have worked on the frictionless and the frictional jamming transition; in the former, we constructed a stress-based statistical mechanics ensemble akin the Gibbs ensemble building up from local force balance (right, from ). For frictional packings, the local connection between sliding contacts and normal modes is crucial for the criticality of jamming .
1. Y. Fily, S. Henkes and M. C. Marchetti, Freezing and phase separation of self-propelled disks, Soft Matter 10, 2132 (2014)
2. S. Henkes, M. van Hecke and W. van Saarloos, Critical jamming of frictional grains in the generalized isostaticity picture, EPL 90 14003 (2010)
3. S. Henkes, C. S. O'Hern and B. Chakraborty, Entropy and Temperature of a Static Granular Assembly: An Ab Initio approach, PRL 99, 038002 (2007)
Current Group members:
Kaja Kostanevec, doctoral student
Dr. Luke Coburn, postdoc
NRP PECRE award, with Dr. Rastko Sknepnek, "Modelling active systems in curved geometries" (2014-15)
EASTBIO doctoral scholarship 'Building and artificial Cornea', with Prof. J. Martin Collinson, student Kaja Kostanjevec (2015-)
BBSRC award "Epithelial Sheet Dynamics during Primitive Streak formation as Active Matter", together with Prof. Kees Weijer and Dr. Rastko Sknepnek (2016-)
I teach the computing half of the 3rd year Research Methods course, PX3017. This course is now fully in the open source language Python. I also teach the relativity parts of PX2510 for physics and science degree students. I also co-teach the more general modern physics 2nd year course PX2512.
From the spring semester on, I will be teaching a part of the classical mechanics course PX4017.
The university runs an Access to Degree program for people who are looking to get into university after a nontraditional pathway. I co-teach the Mathematics Access evening course.