Takayuki Shibata

Bio: Takayuki Shibata is an academic researcher from Toyohashi University of Technology. The author has contributed to research in topics: Vorticella & Etching (microfabrication). The author has an hindex of 14, co-authored 120 publications receiving 825 citations. Previous affiliations of Takayuki Shibata include Ibaraki University.

Characterization of sputtered ZnO thin film as sensor and actuator for diamond AFM probe

Abstract: In order to develop a diamond atomic force microscopy (AFM) probe with a piezoelectric sensor and actuator, we fabricated piezoelectric zinc oxide (ZnO) thin film and measured its piezoelectric constant. First, we developed a simple measurement method for the piezoelectric constant of the thin film, d 31 . This was based on the free vibration theory of cantilever beams. The values of d 31 were determined by measuring an electric charge induced in the piezoelectric thin film on the vibrating cantilever beam and its displacement. Using this method, we evaluated d 31 for ZnO thin film sputtered at various substrate temperatures. The ZnO thin film deposited at temperatures of less than 350 °C was highly c -axis oriented and showed a high piezoelectric constant d 31 of −3.5 pC/N. Using this value, we calculated properties of the diamond cantilever AFM probes of various dimensions and of 5 μm in thickness with a ZnO sensor and actuator of 1 μm in thickness. The resolution of displacement and actuation force for a probe of 150 μm in length and 50 μm in width were estimated to be about 1.5 nm at a resolution of charge measurement of 1×10 −15 C and 7 μN at an applied voltage of 10 V, respectively.

Cofocal microscope, fluorescence measuring method and polarized light measuring metod using cofocal microscope

Abstract: A cofocal microscope, and a fluorescence measuring method and a polarized light measuring method using it, the microscope comprising an incident optical system (10, 10’) for beaming a polarized light from a lighting light source (11) into an object of observation (2) via a matrix type liquid crystal element (22) having a micro-lens array (21) disposed thereon and an object lens (23), a detection optical system (30, 30’) for detecting a reflection light from the object of observation or a fluorescence, and a liquid crystal control unit (52) for controlling the liquid crystal element (22), wherein each micro-lens-related light passed through the micro-lens array (21) is allowed to pass through each pixel (22a) of the liquid crystal element (22) and then into an object lens (23) that forms a plurality of focal points (24) on the object of observation (2), and the polarizing directions of lights passing through respective pixels of the liquid crystal element (22) are controlled by the liquid crystal control unit (52) so as to be orthogonal to one another.

Analysis of lipoproteins by capillary zone electrophoresis in microfluidic devices: Assay development and surface roughness measurements

Abstract: The development of a new assay for lipoproteins by capillary electrophoresis in fused-silica capillaries and in glass microdevices is described in this paper. The separation of low-density (LDL) and high-density (HDL) lipoproteins by capillary zone electrophoresis is demonstrated in fused-silica capillaries with both UV absorption and laser-induced fluorescence detection. This separation was accomplished using Tricine buffer (pH 9.0) with methylglucamine added as a dynamic coating. With UV detection, LDL eluted as a relatively sharp peak with a migration time of ∼11 min and HDL eluted as a broad peak with a migration time of 12.5 min. Fluorescence detection of lipoproteins stained with NBD-ceramide was used with the same buffer system to give comparable results. Furthermore, fluorescence staining of human serum samples yielded results similar to the fluorescently stained LDL and HDL fractions, showing that this method can be used to quantify lipoproteins in serum samples. The method was also used to detect lipoproteins in glass micro-CE devices. Very similar results were obtained in microdevices although with much faster analysis times, LDL eluted as a sharp peak at ∼25 s and HDL as a broad peak at slightly longer time. In addition, higher resolution was obtained on chips. To our knowledge, these results show the first separation and detection of lipoproteins in a microfluidic device using native serum samples. Atomic force microscopy was used to characterize the rms surface roughness (Rq) of microfluidic channels directly. Devices with different surface roughness values were fabricated using two different etchants for Pyrex wafers with a polysilicon masking layer. Using 49% HF, the measured roughness is Rq q = 10.9 ± 1.6 nm and with buffered HF (NH4F + HF) the roughness is Rq = 2.4 ± 0.7 nm. At this level of surface roughness, there is no observable effect on the performance of the devices for this lipoprotein separation.

Fabrication and characterization of diamond AFM probe integrated with PZT thin film sensor and actuator

Abstract: In order to develop a diamond probe with a piezoelectric sensor and actuator for atomic force microscope (AFM), we fabricated lead zirconate titanate (PZT) thin film on a diamond thin film substrate and examined its piezoelectric properties. The PZT thin film was sputtered at room temperature and then annealed to obtain a perovskite structure. After rapid thermal annealing at temperature ramp rate of more than 10 °C/s and at temperatures of more than 500 °C in a nitrogen (N2) ambient, the PZT thin film fabricated on flat Si substrates showed high piezoelectric constant, d31, of about −90 pC/N, as well as in an oxygen (O2) ambient. On diamond thin film substrates, the value of piezoelectric constant was as low as about −20 pC/N due to rough surface of the diamond film. After a poling treatment, however, its piezoelectric constant improved to about −65 pC/N. For realization of a PZT sensor and actuator on a diamond cantilever, the PZT thin film was also successfully patterned by reactive ion etching (RIE) in sulfur hexafluoride (SF6) plasma using a platinum (Pt) upper electrode layer as an etching mask without any damage on the diamond layer. Based on the fabrication and patterning of PZT thin film together with microfabrication techniques of diamond film formed by chemical vapor deposition (CVD), we demonstrate the diamond AFM probe of 150 μm in length, 50 μm in width, and 5 μm in thickness with a PZT sensor and actuator of 1 μm in thickness. The resolution of image sensing and actuation force were estimated to be about 0.4 nm at a resolution of charge measurement of 1×10−15 C, and 17 μN at an applied voltage of 8 V, respectively.

Low-density lipoprotein analysis in microchip capillary electrophoresis systems

Abstract: Due to the mounting evidence for altered lipoprotein and cholesterol-lipoprotein content in several disease states, there has been an increasing interest in analytical methods for lipoprotein profiling for diagnosis. The separation of low- and high-density lipoproteins (LDL and HDL, respectively) has been recently demonstrated using a microchip capillary electrophoresis (CE) system [1]. In contrast to this previous study, the present report demonstrates that LDL analysis can be performed in an uncoated glass microchannel. Moreover, by adding sodium dodecyl sulfate (SDS) to the sample at a concentration well below the critical micellar concentration prior to injection, the LDL peak undergoes a focusing effect and exhibits an apparent efficiency of 2.2 × 107 plates/m. Laser light scattering experiments demonstrate that the low concentration of SDS used does not significantly alter lipoprotein particle size distribution within the time course that the analysis is performed. It is thus hypothesized that SDS nondisruptively coats LDL particles. The peak sharpening effect, observed only when SDS is added solely to the sample, is probably due to a mobility gradient created between the sample and the running buffer. The chip-based method demonstrated here has the potential for rapid analysis and sensitive detection of different LDL forms of clinical relevance.

Drug Discovery Today

Abstract: In recent years, tools for the development of new drugs have been dramatically improved. These include genomic and proteomic research, numerous biophysical methods, combinatorial chemistry and screening technologies. In addition, early ADMET studies are employed in order to significantly reduce the failure rate in the development of drug candidates. As a consequence, the lead finding, lead optimization and development process has gained marked enhancement in speed and efficiency. In parallel to this development, major pharma companies are increasingly outsourcing many components of drug discovery research to biotech companies. All these measures are designed to address the need for a faster time to market. New screening methodologies have contributed significantly to the efficiency of the drug discovery process. The conventional screening of single compounds or compound libraries has been dramatically accelerated by high throughput screening methods. In addition, in silico screening methods allow the evaluation of virtual compounds. A wide range of new lead finding and lead optimization opportunities result from novel screening methods by NMR, which are the topic of this review article.

Piezoelectric Characterization of Individual Zinc Oxide Nanobelt Probed by Piezoresponse Force Microscope

Abstract: Piezoresponse force microscopy (PFM) is used to measure the effective piezoelectric coefficient (d33) of an individual (0001) surface dominated zinc oxide nanobelt lying on a conductive surface. Based on references of bulk (0001) ZnO and x-cut quartz, the effective piezoelectric coefficient d33 of ZnO nanobelt is found to be frequency dependent and varies from 14.3 pm/V to 26.7 pm/V, which is much larger than that of the bulk (0001) ZnO of 9.93 pm/V. The results support the application of ZnO nanobelts as nanosensors and nanoactuators.

Single cell analysis: the new frontier in 'Omics'

Abstract: Single cell analysis: the new frontier in ‘Omics’ Daojing Wang 1 and Steven Bodovitz 2 1. Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 2. BioPerspectives, San Francisco, CA Corresponding author: Wang, D. (djwang@lbl.gov) Cellular heterogeneity arising from stochastic expression of genes, proteins, and metabolites is a fundamental principle of cell biology, but single cell analysis has been beyond the capabilities of ‘Omics’ technologies. This is rapidly changing with the recent examples of single cell genomics, transcriptomics, proteomics, and metabolomics. The rate of change is expected to accelerate owing to emerging technologies that range from micro/nanofluidics to microfabricated interfaces for mass spectrometry to third- and fourth-generation automated DNA sequencers. As described in this review, single cell analysis is the new frontier in Omics, and single cell Omics has the potential to transform systems biology through new discoveries derived from cellular heterogeneity. Single cell analysis: needs and applications Cellular heterogeneity Cellular heterogeneity within an isogenic cell population is a widespread event [1, 2]. Stochastic gene and protein expression at the single cell level has been clearly demonstrated in different systems using a variety of techniques [3-5]. Therefore, analyzing cell ensembles individually with high spatiotemporal resolutions will lead to a

Biomedical applications of thermally activated shape memory polymers

Abstract: Shape memory polymers (SMPs) are smart materials that can remember a primary shape and can return to this primary shape from a deformed secondary shape when given an appropriate stimulus. This property allows them to be delivered in a compact form via minimally invasive surgeries in humans, and deployed to achieve complex final shapes. Here we review the various biomedical applications of SMPs and the challenges they face with respect to actuation and biocompatibility. While shape memory behavior has been demonstrated with heat, light and chemical environment, here we focus our discussion on thermally stimulated SMPs.

MEMS actuators and sensors: observations on their performance and selection for purpose

Abstract: This paper presents an exercise in comparing the performance of microelectromechanical systems (MEMS) actuators and sensors as a function of operating principle. Data have been obtained from the literature for the mechanical performance characteristics of actuators, force sensors and displacement sensors. On-chip and off-chip actuators and sensors are each sub-grouped into families, classes and members according to their principle of operation. The performance of MEMS sharing common operating principles is compared with each other and with equivalent macroscopic devices. The data are used to construct performance maps showing the capability of existing actuators and sensors in terms of maximum force and displacement capability, resolution and frequency. These can also be used as a preliminary design tool, as shown in a case study on the design of an on-chip tensile test machine for materials in thin-film form.