The thickness shear mode (TSM) resonator attached with living cells has been shown to be an effective functional biosensing device to monitor the process of cell adhesion to a surface. In this study, we first monitored the dynamic process of cell attachment and spreading as a function of cell seeding densities. Based on the steady state of cell adhesion to the substrate, a multilayer sensor structure model including a quartz substrate, a cell-substrate interfacial layer and a cell layer was constructed. The thickness of cell-substrate interfacial layer and the viscoelastic properties of human skin fibroblasts (HSF) were then determined by fitting experimental results with the theoretical model. It has been obtained that the thickness of the cell-substrate interfacial layer is 60-80 nm, and the elastic module and viscosity of cell layers are about 13 KPa and 3-4 mPa's respectively. These results are in a good agreement with those measured by other techniques, such as magnetic bead microrheometry, atomic force microscopy (AFM) and Surface Plasmon Resonance Microscopy (SPRM). In addition, knowing that the actin cytoskeleton is important for the mechanical properties of living cells, we investigated the motional resistance change caused by the disruption of actin cytoskeleton induced by fungal toxin Cytochalasin D in the human skin fibroblasts. The results indeed indicate the direct correlation between resistance changes and the disruption of actin cytoskeleton, which are again consistent with the results observed by fluorescence images.
In last few years, with the strong progress in thin film technologies for complex materials systems such as
PZT, ZnO and AlN, thin film bulk acoustic wave resonator (FBAR) and filter concepts are gaining more
and more importance for microwave frequency control applications. For resonators operating in the GHz
range, piezoelectric thin film layer in the order of a few microns with desirable electromechanical
properties (high Q and wide bandwidth) is required. Among these materials, AlN is very attractive due to
that it has a number of interesting properties such as high thermal conductivity, high electrical insulation,
and highly chemical stability. These characteristics make it possible to design and fabricate high frequency
resonators and bandpass filters for signal processing and communication devices. If the thin film bulk
acoustic resonator devices of sufficient performance can be fabricated, they will be the best choice to
replace the current crystal, ceramic or SAW devices due to their compactness and good compatibility with
the high frequency Si or GaAs integrated circuit processing. In this research, onchip AlN thin film
resonator has been investigated. AlN thin films with 0.5 to 2.5μm thickness and c-axis orientation have
been deposited by DC magnetron reactive sputtering method on silicon and sapphire substrates. The
nanoindentation and laser interferometer methods are used to characterize the mechanical properties and
electromechanical properties of the thin AlN film in the composite resonator structure. Patterning of AlN
film and electrode layers has also been studied for the fabrication of onchip thin film bulk acoustic wave
Energy harvesting using piezoelectric material is not a new concept, but its generation capability has not been attractive for mass energy generation. For this reason, little research has been done on the topic.
Recently, wearable computer concepts, as well as small portable electrical devices, are a few motivations that have ignited the study of piezoelectric energy harvesting again. The theory behind cantilever type piezoelectric elements is well known, but the transverse moving diaphragm elements, which can be used in pressure type energy generation is not yet fully developed. The power generation in a diaphragm depends on several factors. Among them, the thickness of each layer is important. In this paper, two diaphragm structures, unimorph and bi-morph, were used to calculate energy generation with varying thickness ratio using piezoelectric constitutive equation. The results of this analysis are presented with an eye toward guidelines for design of useful energy harvesting structure.
This paper presents the design and analysis of a cantilever beam resonator that is driven by a piezoelectric material. In this paper, we shall look at the effects of miniaturizing the resonator. The beam is a bimorph structure with a Lead Zirconate Titanate (PZT) layer and a stainless steel substrate layer. The PZT layer is electroded in segments to form a sensor and actuator pair for feedback to drive the resonator. Key issues are the effects of design choices on the gain required to cause self-oscillation. These choices are placement and sizing of the sensor and actuator. The study is based on an analytical model of the beam. Results show that the gain required for self-oscillation is highly dependent on the actuator and sensor size and location, the mode of vibration and the overall resonator size.
Acoustic source used for Active Noise Control at low frequency (80 - 250 Hz) is designed and developed by using a piezoelectric ceramic actuator and a flextensional panel diaphragm. In order to reach the vibration magnitude and radiation area needed for high and flat sound pressure level in the low frequency range. Pseudo-Shear Universal (PSU) actuator has been used as the driving part which is a new type of multilayer piezoelectric actuator originated from MRL offering the advantages of large displacement and high blocking force; on the other hand, Carbon Fiber Reinforced Composite has been used as the diaphragm material which provides a more rigid structure than conventional loudspeaker paper. A prototype device was fabricated which has the following characterizations: 40 layers PSU actuator with a compact dimension: 38 mm X 50 mm X 23.6 mm. Two of them are needed for a device. Diaphragm area is 126 mm X 152 mm. At quasistatic condition (5 Hz) and at the 0.84 kV/cm electric field, 344 micrometers displacement could be achieved at the apex of the diaphragm resulted from the flextensional amplifying mechanism with an amplification factor more than 11. The sound passive level in the frequency range 100 - 250 Hz shows better flat behavior than the acoustic sources studied earlier such as Double Amplifier and PANEL air transducers which exhibit a significant reduction of sound pressure level in the low frequency range. By a slight modification, it is likely to make this device in a total thickness of 10 - 15 mm range. High and stable sound pressure level as well as thin flat structure make it much more competitive in the whole area of applications for low frequency active noise control.