Research Topics

Self-propulsion breaks equilibrium by locally generating forces, driving the swimmer. It is important that the drive is coupled to the particle and not an external field. Thus a swimming sperm cell is a microswimmer, a sedimenting polymer is not. Sometimes, the activity due to swimming can be mapped to an elevated effective temperature, but more often than not, the activity manifests itself in phenomena inexplicable in equilibrium physics. Often, however, equilibrium concepts and analogies can be used to depict what is going on. For example, collections of self-propelled disks spontaneously "phase separate", motile tissues undergo "glass-like arrest" as density or adhesion increases, or non-equilibrium surface accumulation occurs. The Biological Active Matter group studies microswimmers in many different forms, ranging from generic self-propelled particles and filaments to hydrodynamic simulations of sperm and ciliated microswimmers.

While other forms of growing materials exist (like bacterial colonies or possibly polymers during polymerization), the prime example is biological tissues. Biological tissues form functional parts of organisms composed of cells. They develop during embryogenesis and (most) are under constant renewal over the course of their lifetime. In the past decades, it became more and more clear that physics, and especially mechanics, plays an important role in cellular and tissue growth. The group focuses on particle-based mesoscopic simulations of growing tissues, and on finite-element simulations to model cortical folding due to an imbalance of growth.