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Planar and flexible climbing robots suffer from buckling while climbing on a vertical surface. This paper analyzes two different modes: one-end free buckling and two-ends fixed buckling. As an example for buckling analyses, the paper focuses on an electrostatic climbing robot that features thin body. As the body of the robot has only 2.5 mm of thickness, it is more prone to buckling than any other flexible robots, making it the best example for the buckling problem. Based on the analyses, the paper proposes a buckling-free control strategy for the electrostatic robots. The proposed strategy guarantees the force balance between adhesive force and weight force, as well as the elastic stability of the robot. To implement the strategy, the paper investigates the available region of the proper forces and optimal parameters on the prototype robot. A prototype of climbing robot was developed to verify the analyses and solutions, weighing merely 29 g (excluding battery and control circuits). It successfully climbed up a vertical wall without buckling, carrying the payload of 0.4 N. [ABSTRACT FROM PUBLISHER]

A new bistable micro-electro-mechanical systems actuator functioned by the potassium ion electret technique is presented. We utilize a three-terminal comb-drive actuator with a built-in electret potential. We first describe the operation principle of the bistable device that is driven by a pulse and/or step-function voltage. We next explain the fabrication results and the procedure of the electret polarization. Device operation is demonstrated to determine the switching characteristics from one stable state to another with a 12 V pulse voltage of 300~\mu \texts duration. We also establish bistable switching operation with a step voltage of 5 V or less, which is manageable by a battery for portable equipment. Discrepancy of switching characteristics between the theory and the experiments is discussed from a point of view on the fringe electrical fields between the comb electrodes. [2016-0079] [ABSTRACT FROM AUTHOR]

A three-degrees-of-freedom microelectromechanical systems (MEMS) electrostatic actuator was developed, fabricated, and tested. The actuator utilizes a piston-tube configuration that enables the use of electrodes with a wide area. Therefore, a large output force can be generated. The actuator also utilizes a flexure mechanism in which the in-plane ( $x$ - $y)$ stiffness is high compared with the out-of-plane ( $z$ -axis) stiffness. This flexure mechanism enables a large translation stroke along the $z$ -axis before experiencing lateral pull-in instability. A prototype of the actuator was able to achieve a pure translation (piston-style motion) of $28~\mu $ m at 80 V and an angle of rotation of 0.78° at 70 V. A mass of 1 mg was translated $24~\mu $ m at 80 V, indicating the ability of the actuator to provide high output force. The actuator was fabricated using the Micralyne MicraGEM-Si MEMS fabrication process, in which the pistons and tubes are fabricated in the device layers of two bonded Silicon on insulator (SOI) wafers. The misalignment between the pistons and the tubes using this process was $\sim 0.005$ of the gap between adjacent pistons and tubes. This amount of misalignment leads to a negligible lateral instability effect. [2014-0277] [ABSTRACT FROM AUTHOR]

To further decrease feature sizes, the semiconductor industry heavily improved the photolithography. Photoresist layers are exposed through photomasks and structured accordingly. The underlying substrate is then selectively altered by adding or subtracting material. The unrivaled precision, resolution, and accuracy allow an unmatched level of miniaturization, and several thousand electrical components can be processed simultaneously. This technology was expanded to the fabrication of sensors and actuators, creating microelectromechanical systems. With silicon, the possibilities of further expanding this technology to new dimensions and applications are limited. Reasons are the stiffness, 2.5-D fabrication, and lack of optical transparency. To enable new applications, we present the successful translation of wafer-level fabrication to millimeter-scale actuators. This was achieved by changing the material to ultraviolet (UV)-curable polymers. Based on the electrostatic zipper actuator, avoiding the common pull-in-effect is essential for the successful realization of an acceptable microactuator. Therefore, the bottom electrodes are split and shaped to adjust the generated electrostatic forces, balancing the mechanical restoring forces. Besides the theoretical design, the fabrication technology based on classic photolithography is explained. Experimental results include voltage-dependent deflection measurements, achieving 110- $\mu $ m deflection with 70 V driving voltage. The dynamic response measurements show resonance frequencies of 1.89 kHz. [2014-0181] [ABSTRACT FROM PUBLISHER]

This paper reports a development of a transparent planar electrostatic actuator, which is useful for constructing interactive human–computer interfaces on flat panel displays. The actuator is a pair of transparent plastic films with strip electrodes in three-phase connections. Half of the electrodes in each film are X electrodes, and the rest are Y electrodes; electrostatic forces excited by applying three-phase voltage to these electrodes drive the actuator at speeds proportional to the excitation frequency. The stator film of the actuator has its X and Y electrodes alternately arranged in a four-by-four checkerboard pattern. The slider is a square film with its side twice that of a single square in the stator, with its electrodes separated by diagonal lines. A geometric analysis shows that this electrode arrangement brings position independence of overlapping areas of electrodes. The position independence gives the actuator a uniform thrust force characteristic required for long-stroke planar motion. Based on this concept, we fabricated a prototype by screen-printing. The prototype could exert approximately 100-mN thrust force with an excitation by a pair of 500-V three-phase voltages, and could travel along straight and curved paths within a 132 mm by 132 mm movable range. [ABSTRACT FROM PUBLISHER]

Capacitive comb actuators are widely used as MEMS motors due to their long range of linear motion, low power consumption, and ease of fabrication. Here, we present data from a thin comb capacitive actuator where fringe fields contribute significantly to the device performance. We characterize the observed levitation effect and discuss two methods to control the out-of-plane forces: 1) by means of alternating the comb polarity; and 2) by using an additional electrode below the comb. Considering two alternative designs, it is shown how the levitation force can be mitigated. One design decreases the out-of-plane motion by a factor of two, but also reduces the lateral range. An alternative design proved successful in decreasing out-of-plane motion by 75%, while enhancing the in-plane displacement of the linear comb actuator by over 35%. [ABSTRACT FROM AUTHOR]

This paper reports the modeling and analysis of a linear resonant electrostatic induction motor, with an imbalance in capacitance taken into consideration. The motor is an asynchronous motor consisting of film-type stator and slider with three-phase electrodes, driven by three-phase voltage applied to the stator. The slider electrodes are connected to three coils, which enable the slider voltage to rise high at resonance, producing large thrust force. The motor is highly sensitive to an imbalance of capacitance, particularly at resonance. A model is developed to relate each capacitance formed among the electrodes to symmetrical components of the slider voltage and to the thrust force of the motor. The model indicated that the capacitance imbalance leads to an unbalanced slider voltage with two frequency components and causes thrust force ripple. These nonideal effects were confirmed by experiments, using a motor with geometric asymmetry in its electrode design. [ABSTRACT FROM PUBLISHER]