A novel piezoelectric inchworm actuator driven by one channel DC signal is developed in this paper to simplify excitation signal of the inchworm actuators, and the clamping force of the developed actuator is generated by a DC motor and two permanent magnets. The piezoelectric stack is excited by a sensing signal, which is generated by the separate photoelectric sensor to detect the position of the rotational permanent magnets. A mathematical model is established to predict the motion of the slider. The prototype of the proposed piezoelectric actuator is fabricated, and mechanical output performance is measured. At a voltage of 75 V and frequency of 3.2 Hz, the average output step is 0.241 μm under no-load conditions. The proposed inchworm actuator can be operated by just one channel DC signal and the output displacement is stable, which provides a new idea for the integration design of the piezoelectric actuators in the future.

In order to decrease the backward motion and improve the motion efficiency, a walking type piezoelectric actuator has been proposed with two ‘legs’ based on the parasitic motion of obliquely assembled PZT stacks. The structure and motion principle of the proposed walking type piezoelectric actuator are described, and its experiment system is set up. Experimental results indicate the proposed piezoelectric actuator could reduce the backward motion effectively. The minimum backward rate α = 2.26% is achieved under the condition of the phase difference θ = 180°, the input voltage U = 120 V and the input frequency f = 1 Hz; the minimum stepping displacement is 0.24 μ m under the condition of U = 5 V, f = 1 Hz and θ = 180°; the maximum speed V _max is 2472 μ m s ⁻¹ under the condition of U = 120 V and θ = 180°; the maximum vertical load force F _Vmax = 6850 g under the condition of U = 120 V, f = 1 Hz and θ = 180°. Furthermore, a dynamic model of the whole walking type piezoelectric actuator is established, and it has been employed to simulate the motion of the proposed walking type piezoelectric actuator. Simulation results present a great agreement of experimental results. This study shows a novel idea for the design of piezoelectric actuators to eliminate the influence of backward motion and improve the output efficiency of the actuator.

The piezoelectric inchworm actuator with high-positioning accuracy and large output force is a potential device to implant microelectrode in the invasive brain–computer interface (BCI). However, the traditional piezoelectric inchworm actuator adopts multichannel electrical control signals from external equipment and rigid-to-rigid friction contact to drive, resulting in complex control and uneven friction. To solve the above problems, in this article, magnetorheological elastomer (MRE) is first proposed as the clamping material of the piezoelectric inchworm actuator. An MRE–capillary–cover sandwich structure is adopted to achieve rigid-to-elastomeric clamping. The driving and clamping actions of the actuator are controlled by two cam mechanisms mounted on the same shaft, and a battery can feed the actuator. A kinetic model is established to analyze and predict the actuator motion. Several crucial clamping parameters are explored, and the performance experiments are conducted to evaluate actuator characteristics. A verification experiment is carried out to prove the feasibility of the microelectrode implantation in the pig brain (0.6% agarose gel). The actuator can reach the maximum velocity of 1250.4 μ m/s and the maximum output force of 420 mN; in the forward/backward motion, the minimum step is 0.5837/0.5912 μ m, and the repeatability is 0.0465/0.0469 μ m; thus, the actuator has great application potential in BCI.

The backward motion phenomenon is widespread in inertial impact, stick-slip, and parasitic piezoelectric actuators, and seriously limits the development of these actuators for micro-manipulation applications. To solve this problem, a piezoelectric inertial rotary actuator based on a special wiring scheme is proposed. By changing the pair of piezoelectric vibrators in the traditional actuator to have opposite connection modes, the proposed actuator implements a two-step operating mode over one cycle and suffers no backward motion. Thus, the proposed actuator essentially eliminates the backward motion phenomenon under all conditions. Compared with other methods for controlling backward motion, which typically require additional friction-control or complex signal-control systems, the proposed wiring method has the advantages of simplicity of structure, ease of control, and high stability.