This paper presents the design of a novel flexure-based precision positioning stage with constant output force for biological cell micromanipulation. One uniqueness of the proposed design is that it produces a constant force without using a force controller. Only a motion control is needed to produce a constant output force, which significantly simplifies the system design process. The stage is driven by a piezoelectric actuator through a displacement amplifier. Analytical models of the displacement amplifier and the zero-stiffness structure are established and verified by conducting finite-element analysis simulations. The structure parameters are optimally designed to guarantee the requirement on output force, motion range, and physical size. A prototype stage is fabricated by 3-D printing process and a series of experiments is carried out. Experimental results show that the developed positioning stage delivers a near constant output force with slight fluctuation in the reachable constant-force motion range of 138 mu m. The applications of the developed constant-force stage in biological cell manipulation have been demonstrated through experimental investigations.

Note to Practitioners—A constant-force stage can produce a constant output force without using a force control. It is attractive for biological micromanipulation. This paper presents the design and testing of a novel constant-force flexure stage. The constant force indicates a zero stiffness for the mechanism. The stage mechanism is devised using modified leaf flexure (MLF) to achieve positive-stiffness structure. Bistable beams are used to design negative-stiffness structure by making use of their postbuckling characteristics. Two bistable beams and two MLFs are combined together to construct a zero-stiffness structure. A conventional stage is also fabricated for comparison study. The performance of the proposed constant-force stage has been verified by simulation and experimental studies. Results indicate that the developed stage system has great superiority over conventional one in terms of reducing driving force, increasing motion range, and reducing force fluctuation. Experimental demonstration of bio-micromanipulation has been presented to reveal its potential applications.