Research
Research
Liquid crystals are phases of matter intermediate between the liquid and the solid phase. They are fluids made by components that spontaneously align with each other. When this spontaneous alignment is impossible, topological defects form. We study topological defects in various settings in liquid crystals.
Topological defects in cells. Many cell types align just like liquid crystals do, and form topological defects. In particular, the types of defects formed by monolayers of cells closely resemble those formed by nematic liquid crystals in 2 dimensions. There is increasing evidence that cells near topological defects experience a different level of stress than the other cells. With the use of topographic patterns, we investigate the similarities and differences between these two systems in order to understand more about the self-organization of cells in analogy with self-organization in liquid crystals (main contact: Kirsten Endresen, Aniruddh Murali). We have also investigated the deformation of cells near corners.
In our research, we discovered that some cells accumulate near some type of topological defects. In collaboration with Brian Camley's group, we found that cells tend to divide more frequently near these defects. This suggests that defects help regulate not only dynamics, but also division within a cell layer.
Finally, we have recently realized monolayers of cells that spontaneously fold in 3D structures, controllable from the initial cell alignment.
Here are some links to our papers:
K. Kayirbekov, K. Endresen, K. Sullivan, Z. Zheng, F. Serra, B. Camley, PNAS 2023 https://doi.org/10.1073/pnas.2301197120
A. Murali, P. Awasthi, K. Endresen, A. Goszczak, F. Serra, Soft Matter 2025 https://pubs.rsc.org/en/content/articlelanding/2025/sm/d5sm00093a
And our preprint:
K. Endresen, A. Murali, F. Serra, Actuation of cells in 3D, https://arxiv.org/abs/2411.17834
Topological defects at the phase transition. The control of topological defects in "traditional" liquid crystals is still a challenge in many case. In particular, topological defects change dramatically when liquid crystals undergo a transition to a different type of liquid crystal phase. We have explored various phenomena where we observe either the formation of new types of defects at the phase transition, or we can transform a defect into a different one preserving its location (main contacts: Zhaofei Zheng, Sean Hare).
Here is a link to our papers:
S. Hare, B. Lunsford-Poe, M.S. Kim, F. Serra, "Chiral liquid crystal lenses confined in micro-channels". Materials 13, 3761, 2020 ;
S. Hare, A. De la Vega, F. Serra, Soft Matter, 2025 https://pubs.rsc.org/en/content/articlelanding/2025/sm/d4sm00940a
In addition, we looked at the effect of confining liquid crystals within a polymer network and how the network influences the texture after the phase transition:
Z. Zheng, F. Serra, Phys. Rev. E 2024 https://journals.aps.org/pre/abstract/10.1103/PhysRevE.110.054703
Control of topological defect lines. How can we create an arbitrary pattern of defect lines in nematic liquid crystals? We tried to answer this question in collaboration with Hillel Aharoni's group (Weizmann institute). We found that we can think of defect lines as current lines in a magnetic field - with some differences! With a set of simple rules, we patterned defect lines to draw a heart that "beats" with temperature changes (main contact: Alvin Modin).
A. Modin, B. Ash, K, Ishimoto, R. Leheny, F. Serra, H. Aharoni, PNAS 2023 https://www.pnas.org/doi/10.1073/pnas.2300833120
Control of liquid crystals via photoalignment. One of the challenges in controlling liquid crystals on glass surfaces is that, while it is relatively easy to control the in-plane angle of alignment, it is very difficult to control the out-of-plane angle, also called tilt angle. Alvin Modin has developed a simple technique to spatially pattern the tilt angle using photo-sensitive coating and exposing it to polarized light first and to unpolarized light later (main contact: Alvin Modin).
A. Modin, R. Leheny, F. Serra, Adv. Mater. 2024 https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/adma.202310083
Arrays of topological defects. One of the more useful properties of defects is their capability to self-assemble into regular arrays without need for external manipulation. They can be used to create tunable gratings and other optical components. We have created arrays of the so-called “umbilical defects”, which can be used as diffraction gratings tunable with an external electric field. Thanks to a combination of electric field and an array of polymeric micro-pillars we can make the array regular over large areas. Ah, and we can make quasicrystals of defects! (main contact: MinSu Kim, now Research Professor @ Department of Nano Convergence Engineering, Jeonbuk National University, Korea).
Here are the links to our publications:
M.S. Kim, F. Serra, Adv. Opt. Mater. 2022 https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/adom.202200916
M.S. Kim, F. Serra, Crystals 2020: https://www.mdpi.com/2073-4352/10/4/314/htm
M.S. Kim, F. Serra, Adv. Opt. Mater. https://doi.org/10.1002/adom.201900991