Design of a biaxial soft tissue testing machine

Abstract

The design of a biaxial testing machine to evaluate the mechanical response of biological tissues under controlled tension in two perpendicular directions is presented. This type of testing is essential for determining the elastic constants of materials and for evaluating their anisotropic and orthotropic characteristics. However, the expense of commercial equipment often restricts its accessibility for laboratories whose financial resources are limited. The proposed design relies on both affordable and widely available components, including two-phase NEMA 23 servo motors and DYMH-103 load cells, attached on a perforated acrylic plate. The configuration of the servo motors enables the application of forces perpendicular to the specimen, while the rake clamping system distributes loads more effectively, thereby preventing damage to fragile tissues. The Arduino Mega 2560 board was complemented with TB6600 controllers and HX711 amplifiers to independently manipulate each axis. The design was later validated with the use of simulations in SolidWorks Premium 2022, employing finite element analysis (FEA) to identify critical stress zones and optimize the structure. The findings indicated that the load distribution was sufficient without surpassing the elastic limits of the material, thereby ensuring the safety and functionality of the device during operation. In summary, this design offers a compact, economical and versatile alternative for biomechanical studies.