Facile fabrication of marshmallow-like gels as flexible thermal insulators and liquid nitrogen retention materials: Application to a cryopreserved embryo container

Low bulk density porous monoliths were prepared by using two types of silicon alkoxide methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) as precursors and controlling phase separation under appropriate conditions. By changing the ratio of the aqueous solution to the precursors in the starting composition, it was possible to control the microstructure of the resulting porous monoliths or to prepare microparticles. Those marshmallow-like monoliths with a skeleton diameter of a few micrometers and pore diameter of several tens micrometers has high flexibility against compression and bending, and shows low thermal conductivity of ~30 mW m⁻¹ K⁻¹ at room temperature. We show that those materials can be used as a simple cryopreserved embryo container like small dry shippers by packing gels and adsorbing liquid nitrogen in a vacuum-insulated water bottle.