Non-rigid cutting of soft tissue: physical evidences of complex mechanical interaction process of soft materials

The application of medical waterjet achieves non-rigid separation of soft tissues. The separation effect is the result of the interaction between hydrodynamic and biomechanical nonlinear responses. In this study, a non-rigid cutting model of soft tissue was established based on fracture mechanics and energy conversion processes. It can clearly explain the physical reasons for the advantages of non-rigid separation: The extremely high impact speed, which is difficult to achieve through rigid separation, makes the stress and deformation of the soft tissue smaller. The non-rigid cutting model reveals the impact mechanism of waterjet impact velocity or pressure on the static separation effect. Based on the experimental observation of the physical morphology during the interaction process and the measurement of the dynamic separation rate, imaging evidences for dynamically evaluating the separation effect were proposed. The method of adjusting the separation effect including the splashing behavior of the waterjet was verified. The research results precisely link the application requirements of precision surgery with the physical form of the interactive process, establish a physical basis for expanding the advantages of non-rigid separation of soft tissue and provide guidance for the evaluation of dynamic separation effects.