In this paper we present a simple method for determining the linear thermal expansion coefficients (LTECs) of thin films using compact micromachined structures and common experimental apparatus. The structures can be fabricated by simple silicon-based micromachining techniques with one mask process and in situ along with active devices on the same chip for monitoring the LTECs of the thin film. An analytical expression is derived to relate the LTECs of thin films with the lateral displacements of microstructures. The displacements can be measured directly under an optical microscope with the specimen placed in a heating stage. The analytical expression is free from any correction factor. Furthermore, the accuracy of LTEC determination is significantly enhanced because the analytical expression is not necessary to know the Young's modulus, the Poisson's ratio and the thickness of the thin film. A finite element model is used herein to support the analytical model and also to perform nonlinear analysis. In this research, experimental results with a heavily phosphorus-doped low-pressure chemical vapour deposition polycrystalline silicon film are used to demonstrate the effectiveness of the proposed method. According to the results, the LTEC is dependent on temperature and increases as the temperature rises. The average value of the obtained LTEC is 2.7 × 10−6 °C−1 from room temperature to 400 °C.

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In this paper, a novel wireless and mobile piezoelectric micro robot has been presented. The dimensions of the robot are within several centimeters (such as 7.5cm x 6.5cm x 7.5cm) and the weight is approximate a hundred gram, including the drive and control circuits, the main structure, the piezoelectric beams and the batteries. In contrast to existing mobile micro robots, the actuating mechanism of the proposed robot is piezoelectric bimorph beams, and the driving principle is the piezo-based vibromotor technique with vibration wave (traveling-wave) as drive source to actuate the robot. Since the robot is wireless, the challenge subject of the research is how to minimize the drive and control circuits with high voltage supply (up to 50V) based on battery voltage alone. The robot has speed up to 14 mm/s in 50V and with a frequency of 75Hz on a polished steel surface without extra loading. The robot can bear approximate 96g extra loading.

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This paper presents a novel microactuator driven by shape memory alloy (SMA). First, the helical spring-shaped SMA is fabricated from SMA wire (Ti50%-Ni45%-Cu5%) with one way shape memory effect and 0.6 mm in diameter. Subsequently, a compliant tube-type microactuator driven by helical spring-shaped SMA is developed. The performances of the helical spring-shaped SMA and the compliant tube-type microactuator, such as the response time, the recovery force and the surface temperature in terms of the driving currents, are investigated. The driving circuit system comprising a pulse width modulation (PWM) control circuit is used to drive the actuator. Experiments demonstrate that control of the SMA actuator using PWM effectively reduces the energy consumption and ensures a short cooling time to guarantee a high response time in actuating cycles. Finite element software (COSMOSWorks) is applied for the analysis of the compliant tube-type actuator, which aim is to demonstrate the agreement between the theoretical analysis and experiment as well as to improve the performance of the actuators.