Study Of Laser Microactuators Based On Photoacoustic Mechanism

The micro-opto-electro-mechanical system (MOEMS) and micro/nano technology have recently experienced rapid developments with strong requirement to actuate micrometer-sized and even nanometer-sized targets. Common actuation methods are electromagnetic actuation, electrostatic actuation, piezoelectric actuation, thermoelectric actuation and photothermal actuation, in which electromagnetic, electrostatic, piezoelectric and thermoelectric actuation methods require a conductor to guide the electric current into actuating devices, which is not favorable in micro/nano actuators. By comparing with electric-driven and solar-electric-driven devices, light-driven devices exhibit superior performances in MOEMS area, e.g., easily to actuate and control in remote mode, to have high resistance toward the electromagnetic interference, no requirement of battery and electric wire, and easier miniaturization down to micrometer and nanometer scales. Several mechanisms for light-driven actuators have been reported. However a satisfied performance for actuators has never been achieved. Thus, the development of laser-driven micro-actuators or micro-motors with higher efficiency is urgently demanded. In this work, we successfully design micro/nano-actuators with high amplitude and high response frequencies using photoacoustic mechanism, namely the photoacoustic resonation microactuator (PRMA) and the laser surface acoustic wave microactuator.Firstly, the mechanism of photoacoustic transformation is analyzed in this article. The physical and math model is established for theoretical calculation. The laser heat equation is developed using Gaussian function. The heat conduction equation and thermal-elastic equation is derived from the basic thermodynamic theory.For the study of PRMA, the laser induced resonance on the sample is analyzed. The basic function unit-PRMA beam is designed and studied in the first place, the resonance spectrum, energy, temperature and deformation related to the photoacoustic process is calculated by the simulation software COMSOL Multiphysics. On this basis the PRMA-1 and PRMA-2 with energy storage unit are designed, which can help these PRMAs acquire larger output. The advanced PRMA-3 is then proposed in the following research, which overcomes the shortcomings of PRMA-1, PRMA-2 and realizes miniaturization, large output and quick response speed.The LIGA (Lithographe Galvanoformung Abformtechnik) technology and electric spark linear cutting are used to manufacture the PRMAs. The response features and actuating abilities of the PRMAs are experimented. The displacement is detected using EMAT (Electromagnetic acoustic transducer, EMAT) and compared with the simulation, agreement results are acquired between the theory and experiment. The 10μm and 100μm microspheres are selected as the actuating targets, and the results are monitored by the optical microscope system. The performance of the PRMAs are compared and summarized at last, of which the PRMA-3 performs optimally for both the response feature and actuating ability.In order to overcome the shortcomings of PRMA in some actuating area, the laser SAW actuator is further studied. This kind of actuator utilizes the propagation of SAW to drive the target. The physical and math model are established and the wave characteristic is studied. The optimal design of laser SAW actuator is analyzed. The imagined linear and annular stype SAW actuator are introduced, and a kind of annular stator is designed based on the hypothetical actuator. The laser ultrasonic visualization (LUV) technique is used to detect and observe the propagation of the SAW on the actuator stator. Futhermore the SAW is also experimented by the PZT detector and EMAT to validate the results acquired by the LUV. A micro gear is experimented with the laser SAW actuator, and preliminary results are acquired.In the end, the research achievements are summarized:the novel photoacoustic microactuator is proposed, the corresponding physical and math model are established. The PRMA and laser SAW actuator are designed and studied. Futher improvement of our work is analyzed and expected in the future research.