Straining 3D Hydrogels with Uniform Z-Axis Strains While Enabling Live Microscopy Imaging.

External forces play an important role in the development and regulation of many tissues. Such effects are often studied using specialized stretchers-standardized commercial and novel laboratory-designed. While designs for 2D stretchers are abundant, the range of available 3D stretcher designs is more limited, especially when live imaging is required. This work presents a novel method and a stretching device that allow straining of 3D hydrogels from their circumference, using a punctured elastic silicone strip as the sample carrier. The system was primarily constructed from 3D-printed parts and low-cost electronics, rendering it simple and cost-efficient to reproduce in other labs. To demonstrate the system functionality, > 100 μm thick soft fibrin gels (< 1 KPa) were stretched, while performing live confocal imaging. The subsequent strains and fiber alignment were analyzed and found to be relatively homogenous throughout the gel's thickness (Z axis). The uniform Z-response enabled by our approach was found to be in contrast to a previously reported approach that utilizes an underlying elastic substrate to convey strain to a 3D thick sample. This work advances the ability to study the role of external forces on biological processes under more physiological 3D conditions, and can contribute to the field of tissue engineering.