Abstract
The lack of standardization in tissue testing procedures results in a variety of custom-made devices. In the case of the determination of the mechanical properties of tendons, it is sometimes necessary to adapt the existing laboratory equipment for conducting experiments when specific commercial equipment is not applicable to solve issues such as proper gripping to prevent tendon slipping and rupturing, gripping control and manoeuvrability in case of tendon submerging and without contamination of the testing liquid. This paper presents the systematic development, design, and fabrication using 3D printing technology and the application of the double-acting linear pneumatic actuator to overcome such issues. It is designed to do its work submerged in the Ringers’ solution while gripping the tendon along with the clamps. The pneumatic foot valve unit of the Shimadzu AGS-X tensile testing machine controls the actuator thus preventing Ringers’ solution to be contaminated by the machine operator during specimen set-up. The actuator has a length of 60 mm, a bore of 50 mm, and a stroke length of 20 mm. It is designed to operate with an inlet pressure of up to 0.8 MPa. It comprises the cylinder body with the integrated thread, the piston, the piston head, and the gripper jaw. Fused deposition modeling (FDM) has been used as the 3D printing technique, along with polylactic acid (PLA) as the material for 3D printing. The 3D printed double-acting linear pneumatic actuator was developed into an operating prototype. This study could open new frontiers in the field of tissue testing and the development of similar specialized devices for medical purposes.
Highlights
Product design and development sometimes touch the boundaries of their usual field of activity, occasionally jumping into other scientific disciplines such as medicine to provide answers
Most of the knowledge about the biomechanical properties of tendons and ligaments comes from the tensile testing procedures in which the specimen is placed in the jaws of the machine and tensile force is applied to the breaking point [1,2,3,4,5,6]
3D printing has been used to manufacture soft pneumatic actuators that operate at relatively low supply pressures, 3D printing has not been used to manufacture conventional pneumatic actuators, such as the piston-cylinder assembly, that can operate at standard pneumatic supply pressures
Summary
Product design and development sometimes touch the boundaries of their usual field of activity, occasionally jumping into other scientific disciplines such as medicine to provide answers. The titanium alloy lateral block boards were used to prevent the soft tissues from being pushed out during compression, while the nylon asymmetric tooth jaws were used to grip and hold the soft tissues The ability of this new type of clamp was tested by stretching five bovine tendons to failure on the tensile and compression testing machine; none of them showed slippage before failure, and the maximum tensile force was 6.87 kN. An expensive and massive device is not needed to grip the tendon and to avoid slippage of the tendon due to the thawing of the tissue during the experiment Other advantages of this clamp are its relatively small size and weight, low labour requirement and short fabrication time due to the commercially available serrated plastic material. The other clamping techniques can be found in [11,12,13,14]
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