Probing active nematics with in-situ microfabricated elastic inclusions

Synthetic active biomaterials are valuable tools to explore and understand the organization and dynamics of complex living systems. Proposed theories face limitations in their use since they are based on a few parameters that are challenging to measure.  Our work introduces a novel microfabrication method for the in-situ polymerization of hydrogel structures within a tubulin/kinesin active nematic gel. This method allows to imprint columnar objects of any size and shape, and with a wide range of stiffness: from rigid to compliant structures that can be deformed by forces exerted by the active material. 

After callibrating the mechanical properties of the hydrogel, our protocol has allowed us to measure the shear viscosity, activity parameter, and the bend rigidity of the active biofilaments. Our measurements also enable a quantitative mapping of the forces around topological defects in the active material, which not only play a fundamental role in biological organization but also hold the potential to drive advancements in biohybrid machines in the future. 

Beyond these quantitative results, our fabrication method will enable a new generation of experiments where channels and obstacles with arbitrary rigidity can be instantaneously included into encapsulated active soft materials.