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Sponges are animals that inhabit many aquatic environments while filtering small particles and ejecting metabolic wastes. They are composed of cells in a bulk extracellular matrix, often with an embedded scaffolding of stiff, siliceous spicules. We hypothesize that the mechanical response of this heterogeneous tissue to hydrodynamic flow influences cell proliferation in a manner that generates the body of a sponge. Towards a more complete picture of the emergence of sponge morphology, we dissected a set of species and subjected discs of living tissue to physiological shear and uniaxial deformations on a rheometer. Various species exhibited rheological properties such as anisotropic elasticity, shear softening and compression stiffening, negative normal stress, and non-monotonic dissipation as a function of both shear strain and frequency. Erect sponges possessed aligned, spicule-reinforced fibres which endowed three times greater stiffness axially compared with orthogonally. By contrast, tissue taken from shorter sponges was more isotropic but time-dependent, suggesting higher flow sensitivity in these compared with erect forms. We explore ecological and physiological implications of our results and speculate about flow-induced mechanical signalling in sponge cells. 

A ubiquitous structural feature in biological systems is texture in extracellular matrix that gains functions when hardened, for example, cell walls, insect scales, and diatom tests. Here, we develop patterned liquid crystal elastomer (LCE) particles by recapitulating the biophysical patterning mechanism that forms pollen grain surfaces. In pollen grains, a phase separation of extracellular material into a pattern of condensed and fluid-like phases induces undulations in the underlying elastic cell membrane to form patterns on the cell surface. In this work, LCE particles with variable surface patterns were created through a phase separation of liquid crystal oligomers (LCOs) droplet coupled to homeotropic anchoring at the droplet interface, analogously to the pollen grain wall formation. Specifically, nematically ordered polydisperse LCOs and isotropic organic solvent (dichloromethane) phase-separate at the surface of oil-in-water droplets, while, different LCO chain lengths segregate to different surface curvatures simultaneously. This phase separation, which creates a distortion in the director field, is in competition with homeotropic anchoring induced by sodium dodecyl sulfate (SDS). By tuning the polymer chemistry of the system, we are able to influence this separation process and tune the types of surface patterns in these pollen-like microparticles. Our study reveals that the energetically favorable biological mechanism can be leveraged to offer simple yet versatile approaches to synthesize microparticles for mechanosensing, tissue engineering, drug delivery, energy storage, and displays.