Novel Acoustic Wave Microsystems for Biophysical Studies of Cells

The platform presented in this study exploits high frequency acoustic interaction and uses direct coupling of Rayleigh type SAWs with various samples placed inside microcavities to analyze their structural properties. The proposed microsystem was analyzed using finite element methods. Prototype devices were fabricated on quartz and lithium niobate in a cleanroom environment. Soft microprobes and microchannels were fabricated out of SU-8 and PDMS, respectively. Experimental results are given first for analysis of high glycerin content in deionized water as wells as counting and size differentiation of polystyrene microbeads. Ultimately, biological cells are sensed and characterized. After tumor cells in media are transported to and trapped in microcavities using soft microprobes, the proposed platform uses SAW interaction between the substrate and the cells to extract their mechanical stiffness based on the ultrasound velocity differentials. Small populations of various types of cells such as MCF7, MDA-MB-231, SKBR3, and JJ012 were characterized and characteristic moduli are estimated for each cell population. In conclusion, the results indicate that high frequency stiffness modulus is a possible biomarker for aggressiveness of the tumor and that microcavity coupled SAW devices are a good candidate for non-invasive interrogation and high frequency biophysical studies of single cells. The proposed system is a successfully miniaturized ultrasonic biosensor and can be integrated with microchannels to obtain higher throughput upon refinement of the design as evidenced by the initial results with microfluidics. Improvement in performance and signal strength is also shown to be possible through matching circuits as demonstrated

A Novel Surface Acoustic Wave Sensor for Microparticle Sensing and Quantification

This paper presents a new method for sensing and the quantification of the number of solid microparticles using surface acoustic wave (SAW) devices. In contrast to the standard mass loaded delay line approach, microcavities with varying geometrical shapes and sizes are formed between SAW interdigitated transducer pairs. The system operation relies on the resonance condition occurring inside the microcavity through the coupling of Rayleigh waves to the sample, and the output phase angle is used for obtaining measurement results. It is shown through measurements that it is possible to interact with polystyrene solid microbeads trapped inside the microcavity and extract information about the size of the sample. Furthermore, the number of microbeads placed in a single file along the microcavity width can be quantified using this platform. Experimental results are compared and verified with finite-element method simulations. In essence, this novel approach resulted in a platform capable of analyzing sample volumes less than 10 pL in a non-invasive manner. For size differentiation, experimental phase shifts of 0.14° ± 0.05°, 0.81° ± 0.26°, and 3.54° ± 0.49° were obtained in rectangular microcavities for 10, 15, and 20 \mu \text{m} microbeads, respectively. On the other hand, a distribution of phase shifts as 0.51° ± 0.19°, 0.98° ±0.12°, and 1.34° ± 0.15° are obtained for counting one, two, or three microbeads, respectively. The proposed system was designed, simulated, fabricated, and tested successfully

A novel approach for differentiation of liquid samples with surface acoustic wave transducers and embedded microcavities

We discuss a novel method for sensing and differentiation of analytes trapped in a microcavity with an emphasis on liquids. The proposed sensing mechanism relies on capturing the analyte of interest in a microcavity etched on the delay line in contrast to the conventional mass loading method. The structure mainly consists of input and output interdigitated transducer (IDT) electrodes in an otherwise standard delay line configuration operated in Rayleigh mode along with a microcavity etched between the IDTs to trap minute amounts of liquids. Firstly, the responses of the system with the microcavity are explored using finite element method (FEM) analysis. Then, experimental results from delay lines on two different substrates, namely, Y-Z lithium niobate and ST-X quartz are analyzed. The system can distinguish between liquids with glycerin concentrations ranging from 60% to 90% in water and less than 5pL in volume in the high frequency range of 197MHz and 213MHz based on frequency and phase shift readings. Lithium niobate samples with 1.2μm deep microcavities provide an overall frequency sensitivity of −7.7kHz/(% glycerin). Quartz samples with 8.5μm deep microcavities have a sensitivity of −0.13°/(% glycerin). The minimum density–viscosity product experimentally differentiated using embedded microcavities is 1.9kg/m2√s. It is concluded that this method can be used to trap and interrogate minute amounts of liquids with different properties. Experimental results demonstrate that our approach can possibly be extended to certain solids, and to more complex structures like single biological cells

Microcantilever suspension using hard masks and a two phase RIE method

[Display omitted] •A cost effective RIE method consisting of two phases is used for suspension.•The two sequential phases of etching were anisotropic and isotropic, respectively.•Process gases are SF6, CF4, and O2 which were optimized separately for each phase.•100μm×300μm microcantilevers were suspended in a total of 90min.•Etch progression analysis using contrast differentials in SEM are shown. This study presents the application of simple and efficient Reactive Ion Etching (RIE) methods to suspend microcantilevers using a two electrode plasma reactor. The process consists of two steps and poses a viable, robust, and cost effective alternative to other methods such as XeF2 vapor etching. Aluminum hard mask was employed for general purpose use in processes where materials other than silicon are used to form the microcantilever. Successive etching steps of silicon substrate with SF6/O2 and CF4/O2 plasmas were applied sequentially in a two phase configuration where the first phase is relatively anisotropic and the second phase is more isotropic. This allowed for suspension of microcantilevers while maintaining well-defined undercut characteristics. Etch characteristics were measured for different process parameters, and the effect of O2 concentration, power, and pressure on etch rate and isotropy was presented. The selectivity to aluminum mask was measured to be larger than 250:1 in the used recipes. It was also shown on the test structures that the amount of undercut is observable as contrast differentials using simple SEM imaging techniques on metal film hard mask. During individual characterization of etch profiles, isotropy parameters varying between approximately 0.4–0.95 were obtained under different etch conditions. The maximum etch rates of SF6 based and CF4 based etch recipes were found to be 30.5μm/min and 3.2μm/min, respectively, for varying conditions. Aluminum microcantilevers with dimensions of 100μm×300μm were successfully released after 90min of processing with 30μm of travel distance to the underlying notch

A novel surface acoustic wave sensor with embedded microcavities for size differentiation of solid microparticles

Here we present a novel method for sensing of solid microparticles using surface acoustic wave (SAW) devices. In contrast to the standard mass loaded delay line approach, microcavities with varying geometrical shapes and sizes are formed between SAW interdigitated transducer (IDT) pairs. The system operation relies on the resonance condition occurring inside the microcavity through coupling of Rayleigh waves to the sample, and the output phase angle is used for obtaining measurement results. We show through measurements that it is possible to interact with polystyrene solid microbeads trapped inside the microcavity and extract information about the size of the sample. Experimental results are compared and verified with finite element method (FEM) simulations. In essence, this novel approach resulted in a micro acoustic microscopy device with the capability of analyzing sample volumes less than 10 pL in a non-invasive manner. Experimental phase shifts of 0.14°±0.05°, 0.81°±0.26°, and 3.54°±0.49° were obtained in rectangular microcavities for 10 μm, 15 μm, and 20 μm microbeads, respectively The proposed system was designed, simulated, fabricated, and tested successfully

Biosensors in the small scale: methods and technology trends

This study presents a review on biosensors with an emphasis on recent developments in the field. A brief history accompanied by a detailed description of the biosensor concepts is followed by rising trends observed in contemporary micro- and nanoscale biosensors. Performance metrics to quantify and compare different detection mechanisms are presented. A comprehensive analysis on various types and subtypes of biosensors are given. The fields of interest within the scope of this review are label-free electrical, mechanical and optical biosensors as well as other emerging and popular technologies. Especially, the latter half of the last decade is reviewed for the types, methods and results of the most prominently researched detection mechanisms. Tables are provided for comparison of various competing technologies in the literature. The conclusion part summarises the noteworthy advantages and disadvantages of all biosensors reviewed in this study. Furthermore, future directions that the micro- and nanoscale biosensing technologies are expected to take are provided along with the immediate outlook

A Thermal Conductance Optimization and Measurement Approach for Uncooled Microbolometers

This paper introduces an optimization approach of thermal conductance for single level uncooled microbolometer detectors. An efficient detector design is required due to the limited availability of silicon area per pixel, i.e., the pixel pitch, and due to the capabilities of the fabrication line. The trade-offs between physical parameters are studied to attain the best performance, including the thermal conductance, the thermal time constant, the effective temperature coefficient of resistance (TCR), and the active area, where the main performance criterion has been selected as the Noise Equivalent Temperature Difference (NETD). A microbolometer pixel is modeled using theoretical formulations, and simulations are carried out using this model, and then, the accuracy of the model is verified by Finite Element Method (FEM) analysis. Consequently, optimum design parameters, such as the length of the support arms and the choice of interconnect metal can be extracted from the simulations for a defined process flow. Furthermore, a simple and reliable method for measuring the thermal conductance has been introduced. With this method, it is possible to accurately measure the thermal conductance in a large pixel temperature range, which is required especially for high thermal resistance microbolometers as they heat up rapidly in vacuum. The validity and accuracy of this method are also verified by comparing the simulation results with measurements performed on a single pixel microbolometer that is designed and fabricated based on the optimization approach outlined in this paper

Synthesis of ZnO nanowires using lower temperature vapor based methods

In this paper, we elaborate on protocols for growing ZnO nanowires using different vapor deposition techniques to provide a comparative study for low temperature based deposition. Effects of various parameters ranging from process temperatures to material compositions were investigated. Growth from ZnO thin film seed layers and catalytic growth using Au nanoparticles were performed as well as growth on blank Si substrates for comparison. Detailed results of SEM and XRD studies are presented for the ZnO nanowires. The lowest temperature achieved was approximately 750 °C with nanowires having diameters of 30-50 nm and lengths of 200-300 nm using VS method with a ZnO thin film seed to obtain complete surface coverage. In order to make the vapor based methods compatible with biosensors with monolithic readout circuits, the conventional thermal budget of commonly employed CMOS technology (usually around 450 °C) needs to be considered. Thus, lower temperature growth is preferable. In this regard, we address the temperature aspect of the growth for CMOS compatibility. We identify the effects of important process parameters and present a comprehensive investigation and comparative study of various factors on ZnO nanowire growth

The information requirements and self-perceptions of Turkish women undergoing hysterectomy

WOS: 000369318000036PubMed ID: 27022368Objectives: To investigate the affects, information requirements and self-perceptions of Turkish women undergoing hysterectomy. Methods: A descriptive cross-sectional study was conducted on 37 Turkish women undergoing hysterectomy and followed in a gynecology unit of a state hospital in Canakkale, Turkey, between February and August 2012. Data were collected before discharge with a questionnaire composed of 32 questions. Percentage distributions and Chi-square test were used in the evaluation of the data. Results: There was a significant relationship between fear of anesthesia and number of pregnancies (p=0.007) and between death during surgery and number of pregnancies in the preoperative period (p=0.027). The relationship between knowing type of surgery and knowing when sutures would be removed was also significant in post-operative period (p=0.045). In addition, there was a significant relationship between women's living only with their husbands and worrying about not having children anymore (p=0.032). Conclusion: The women's information needs were high and women's self-perceptions had been affected negatively after hysterectomy. It is recommended that nurses, primarily health professionals should have adequate knowledge on comprehensive care and psychosocial support after hysterectomy