Jikui Luo

196Progress in ZnO thin films and nanostructures for the acoustic wave microfluidic and sensing applications are reviewed in this chapter. ZnO thin films with good piezoelectric properties possess large electromechanical coupling coefficients and can be fabricated for the surface acoustic wave (SAW) and film-bulk acoustic resonator (FBAR) devices with a good acoustic performance. The SAWs can be excited to mix, stream, pump, eject, and atomize the liquid, and precision sensing can be performed using SAWs and FBARs. Therefore, the ZnO SAW devices are attractive to be integrated into a lab- on-chip system where the SAWs can transport bio-fluids to the desired area, mix the extracted DNA or proteins, and detect the changes of the signals using SAWs or FBARs. The ZnO SAW and FBAR devices in combination with different sensing layers could also be used to successfully detect gas, UV light, and biochemicals with remarkable sensitivities. This chapter reviews the progress in Zinc oxide (ZnO) thin films and nanostructures for the acoustic wave microfluidic and sensing applications. ZnO thin films with good piezoelectric properties possess large electromechanical coupling coefficients and can be fabricated for the surface acoustic wave (SAW) and film-bulk acoustic resonator (FBAR) devices with a good acoustic performance. The ZnO SAW devices are attractive to be integrated into a lab- on-chip system where the SAWs can transport bio-fluids to the desired area, mix the extracted DNA or proteins, and detect the changes of the signals using SAWs or FBARs. ZnO-based microfluidics is presented as one of the key the main applications for ZnO thin films and nanostructures. The electronic band structure of ZnO is one of the basic properties and has been investigated through the theoretical calculations and experimental determination. The size reduction of the ZnO materials to nanoscale can enhance the piezoelectricity.

Grasping and manipulating small or micro-objects is critical for a wide range of essential biological applications, such as the assembly of small parts in microsurgery, nerve repair, and selective manipulation or separation of cells, microbes, localized cell probing, measurement etc. Different microgripping and releasing mechanisms have been reviewed and discussed in this chapter. Smart microgrippers or microcages based on the combination of highly compressively stressed diamond-like carbon (DLC) and electroplated Ni bimorph structures or SU8 polymer layer and shape memory thin films have been designed, simulated, fabricated, and characterized. Theoretical, simulation, and experimental results revealed that the radius of curvature of the bimorph layer can be adjusted by varying the DLC film stress and thickness ratio of the DLC to metal or polymer layers. The angular deflection of the bimorph structures can be adjusted by varying the finger length. The radius of curvature of the microcage is in the range of 20-100 mu m, suitable for capturing and confining micro-objects with similar sizes. The operation of this type of device is based on either (1) a large difference in thermal expansion coefficients of the DLC and the metal or polymer layers or (2) the shape memory effect. Electrical tests have shown that these microcages can be opened efficiently utilizing a power smaller than 20 mW and a frequency of 100 Hz.

This paper presents a non-invasive, self-powered system that can be used in the suppression of vibrations medically affecting people. Mechanical vibratory signals are picked up by piezoelectric sensors. Magnitude and frequency information is given as a voltage. Electronic circuitry filters, amplifies and gates the signal before either storing or manipulating and feeding the signal back to piezoelectric actuators, at the required phase and amplitude to suppress the vibrations. Outcomes of the paper show the use of different flexible piezoelectric materials to effectively increase energy storage and reduce vibrations. Advances in low power electronics have provided a means of solely powering devices from piezoelectric harvested energy, especially with the advent of piezoelectric ceramic fibre composites. Energy harvesting has been implemented in hand cranked radios, shake powered flashlights, wind farms, and solar energy. Through the use of standard electronic techniques acquired power can be converted, stored and regulated. Piezoelectric fibre composites are capable of extracting energy from mechanical forces with the aim of collecting a portion of the mechanical energy associated with normal activates and utilising this in the creation of a self powered device to suppress low level vibrations.