Research interests
We design an amorphous material with a full photonic bandgap inspired by how cells pack in biological tissues. The size of the photonic bandgap can be manipulated through thermal and mechanical tuning. These directionally isotropic photonic bandgaps persist in solid and fluid phases, hence giving rise to a photonic fluid-like state that is robust with respect to fluid flow, rearrangements, and thermal fluctuations in contrast to traditional photonic crystals. This design should lead to the engineering of self-assembled nonrigid photonic structures with photonic bandgaps that can be controlled in real time via mechanical and thermal tuning.
Related Publication:
X. Li, A. Das, D. Bi "Biological Tissue-inspired Tunable Photonic Fluid" PNAS,115 (26) 6650-6655, (2018)
Related Publications:
X. Li, A. Das, D. Bi “Mechanical Heterogeneity in Tissues Promotes Rigidity and Controls Cellular Invasion", Phys. Rev. Lett.,123, 058101 (2019)
T. Fuhs et al, “Rigid Tumors Contain Soft Cancer Cells", Nature Physics, https://doi.org/10.1038/s41567-022-01755-0 (2022)
Heterogeneity amongst cells in a tumor has been recognized as one of the hallmarks of cancer. This so-called intratumor heterogeneity is thought to facilitate metastasis by allowing a cellular community the flexibility and efficiency to adapt to new environments. It is also largely responsible for therapeutic resistance. Cellular differences within a tumor result from an interplay of both genetic and extrinsic influences. Whereas fitness or genotypic heterogeneity has been studied extensively, the role of mechanical heterogeneity in a tumor or cellular collective is still not well understood. In this work, we study explicitly the effect of heterogeneity on the mechanics of the confluent cell monolayer using the vertex model. We also connect tissue rigidity to cellular migration using model for the invasion of a single metastatic cell in a heterotypic microenvironment of the tissue.
Related Publication:
X. Li, D. Bi “Nature-inspired designs for disordered acoustic bandgap materials", Soft Matter (2023)
We introduce an amorphous mechanical metamaterial inspired by how cells pack in biological tissues. The spatial heterogeneity in the local stiffness of these materials has been recently shown to impact the mechanics of confluent biological tissues and cancer tumor invasion. Here we use this bio-inspired structure as a design template to construct mechanical metamaterials and show that this heterogeneity can give rise to amorphous cellular solids with large, tunable acoustic bandgaps. Unlike in acoustic crystals with periodic structures, the bandgaps here are directionally isotropic and robust to defects due to their complete lack of positional order. Possible ways to manipulate bandgaps are explored with a combination of the tissue-level modulus and local stiffness heterogeneity of cells. To further demonstrate the existence of bandgaps, we dynamically perturb the system with an external sinusoidal wave in the perpendicular and horizontal directions. The transmission coefficients are calculated and show valleys that coincide with the bandgaps.
We develop a composite hydrogel that mimics changes in the stiffness of the tumor microenvironment to explore how physical confinement influences individual and collective cell migration in 3D spheroids. The mechanical properties of the hydrogel can be tuned through crosslinking and crosslink reversal. Using this hydrogel system and computational Self-Propelled Voronoi modeling, we show that spheroid sorting and invasion into the matrix depend on the balance between cell-generated forces and matrix resistance. Sorting is driven by high confinement and reducing matrix confinement triggers a collective fluidization of cell motion. The findings support a model where matrix stiffness modulates spheroid sorting and unjamming in an adhesion-dependent manner, providing insights into the mechanisms of cell sorting and migration in the primary tumor.
Related Publication:
G. Cai et al, “Matrix stiffness modulates 3D spheroid sorting and burst-like collective migration", Acta Biomaterialia, https://doi.org/10.1016/j.actbio.2024.03.007 (2024)