Standardized tensile testing of soft tissue using a 3D printed clamping system
Biomechanical testing of soft tissues forms the backbone in the experimental validation of tissue engineering and for modelling purposes. The standardized testing of soft tissues requires different experimental protocols and fixtures compared to hard tissues or non-biological materials due to their characteristics. Some of the most commonly-used clamping methods for soft tissue testing affect the tissues’ mechanical properties as chemicals are involved to decelerate degradation and autolysis. Moreover, they are unsuitable for standardized and high-throughput testing. Material slippage is also a recurrent unwanted influence on the testing routine with impact on measurement validity. Addressing these issues, this protocol presents a clamping system for simplified testing of biological soft tissues with all necessary components manufactured utilizing 3D printing technology. Templates allow trimming the samples into standardized shapes and sizes while preparation tables facilitate clamping in a fixed distance. The key parts of the system are clamps with a pyramid design, which allow to mount biological soft tissues before transferring it into the testing device and minimize material slippage during tensile testing. Flexible holder arms are used to transfer samples from preparation tables into the testing device and simplify positioning. Mechanical testing itself is performed with digital image correlation (DIC) for precise strain measurements. Files included: STL files for 3D printing and CAD files (PTC Creo): Clamp flat pyramids, Clamp flat pyramids, Cutting plate bottom, Cutting plate top, Holder arm, Molding device bottom, Molding device top, Mounting adapters, Preparation table Video: Standardized soft tissue tensile testing Also see publication: Utilization of 3D printing technology to facilitate and standardize soft tissue testing Nature Scientific Reports https://doi.org/10.1038/s41598-018-29583-4
Steps to reproduce
For optimal results the application of a rigid material with 100% infill (printed with a 0.4 mm nozzle and 0.15 mm layer height) is strongly recommended for the clamps (PLA works fine and was used for several studies). PLA is also recommended for the preparation table and templates due to good printability and low warping (0.4 mm nozzle, 0.15 mm layer height, 15% infill). TPU is recommended for holder arms and mounting adapters (0.4 mm nozzle, 0.20 mm layer height, 15% infill) as it is an elastic material and therefore easy to attach to and remove from the clamps. All STL files are already oriented in the recommended orientation for printing without any support.