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Fecal incontinence caused by sphincter dysfunction is a difficult medical problem which has not been fully resolved. An artificial anal sphincter (AAS) is considered an eventual choice as prosthesis to maintain anal continence. Currently, Acticon Neosphincter, the only device certified by the US Food and Drug Administration can not maintain the long-term effectiveness. The crucial problem of this study was to keeping long-term biomechanical compatibility between the AAS and the surrounding tissue. This paper presented a design of an AAS with constant force or pressure using superelastic shape memory alloy (SMA) to solve the problem. A C-shaped superelastic SMA sheet was optimized to obtain constant force or pressure by combing finite element analysis with ANSYS and genetic algorithm in MATLAB. The result of optimization was validated by performing an experiment. The optimized model was embedding into the device to realize clamping the soft tissue with constant force, which was confirmed by experiments. [ABSTRACT FROM AUTHOR]