"Liquid crystal patterns to command living matter"

Lavrentovich Figure 1

Figure 1. (a) Director lattice with +1 and -1 defects commands (b) bacteria to swim counterclockwise around +1 defects and avoid cores of -1 defects; (c) tissue of human dermal fibroblasts patterned by a liquid crystal elastomer substrate.

Microscale biological systems such as swarms of swimming bacteria and cell tissues demonstrate fascinating out--of-equilibrium dynamics. These dynamics are difficult to control by factors other than transient gradients, such as gradients of nutrients; visual, acoustic and tactile communication channels that humans use to control large animals are not effective at the scale of micrometers. To establish communication with microscale biological systems, we propose to use special classes of nontoxic liquid crystal with long-range orientational order. The anisotropy axis of the liquid crystal can be designed as uniform or be pre-patterned into various structures. We explore how the patterned liquid crystals can be used to command, and sometimes even enable, dynamics in systems of (i) swimming bacteria; (ii) living tissues of human dermal fibroblast (HDF) cells. Topological defects impact the biological microstructures most strongly, causing spatial variation of bacterial concentration, controlling their dynamics, and defining living cells' orientation and phenotype, Fig. 1. The control of active living matter by patterned liquid crystals might result in new approaches to harness the energy of collective motion for micro-robotic, biomechanical, and sensing devices.

The REU students will test how different liquid crystal environmental patterns affect the individual and collective behavior of swimming nonvirulent bacteria and the growth of living tissues. Significance of the proposed research will be in the development of concepts to command the behavior of microorganisms, direct them towards targeted locations, manipulate their distribution and concentration in space and time, thus triggering biochemical effects such as quorum sensing and fertilization. This knowledge will advance the science of active matter and microbiology. It could inspire new approaches to technologies of microscale robotics, regenerative medicine, fabrication, transport, sensing, and delivery at the microscale, as well as alternative treatments of infectious diseases.