Characterization of AlGaAs microstructure fabricated by AlGaAs/GaAsmicromachining

An AlGaAs/GaAs micromachining technique that is compatible with laser diode fabrication process is described. AlGaAs structural layers and GaAs sacrificial layers are prepared by metal organic vapor phase epitaxy. Reactive dry etching with chlorine is used to fabricate high-aspect structures. Peroxide/ammonium hydroxide solution is used for selective etching of the sacrificial layer. Since the epitaxial layer has low stress, precise undeformed microstructures are obtained. Good compatibility with the LD process makes it possible to integrate microcantilever beams with LD's without degradation of LD characteristics. Microcantilever beams of AlGaAs are characterized by directly measuring stiffness and natural frequencies. A fracture test is also performed on the AlGaAs microcantilever beams. The average fracture stress of AlGaAs is found to be 1 GPa at 1% strain, which shows that the material is strong enough to support the micrometer scale structures     

Structural study of degraded ZnMgSSe blue light emitters

Using electroluminescence (EL) topography and transmission electron microscopy (TEM), we investigated the nonluminescent regions which form while current is being injected into ZnMgSSe/ZnSSe/ZnCdSe-based blue light emitters. Small dark spots were observed just after turn-on and spread out forming rough nonluminescent triangles in the <100> directions in the EL image of the active region. TEM studies showed that the small dark spots are pre-existing stacking faults originating at the substrate/epitaxial layer interface. The nonluminescent triangles were found to be a dense region of dislocation dipoles and dislocation loops. Each dipole was aligned along two <110> directions in the {111} planes. The Burgers vectors were of the type a/2<011> inclined at 45° to the (001) junction plane.     

Control of secondary flow in concentrically traveling flow on centrifugal microfluidics

This paper reports a fundamental study of the stripe laminar flow pattern on a centrifugal microfluidic device with the goal of realizing a sedimentation-based, continuous mode particle separation technique. Microfluidic channels were designed with a concentrically integrated microchannel, and the patterning of the flow in the channel was investigated. A significant secondary flow was observed as a preliminary result. We conclude that the origin of this secondary flow was not the Dean force, because it was observed in a straight microchannel, but was not observed in curved channel during the spinning of the system at rest. The transition of the pattern was investigated using a simulation and experiment, and the flow pattern’s dependence on the rotational speed was determined, which suggested that the origin of the secondary flow was the Coriolis force. The significance of the secondary flow was controlled by adjusting the rotational speed of the disk, and the flow rate and laminar flow patterns were controlled by the stripe flow pattern.     

Polytetrafluoroethylene processing characteristics using high-energy X-ray

Polytetrafluoroethylene (PTFE) microstructures’ processing characteristics using X-ray photo dcomposition and desorption are studied in the highest energy region (2 keV to >12 keV). While the exposed surface states are seen melting and boiling from the remaining bubble structure of the irradiated surface, basic photochemistry of PTFE is also same as previous reports and high-aspect ratio structures are successfully formed. We developed new Ni stencil electroformed stencil masks and successfully fabricated first and practical example of PTFE micro fluidic parts. The characteristics of fabricated micro fluidic parts, a PTFE fluid filter for vertical fluid flow operation which works as passive valve, agreed with the calculated results. This suggests that the accuracy of patterning is adequate to apply this technique to fabricate microfluidic parts and other various microparts.     

Enzyme-linked immunosorvent assay using vertical microreactor stack with microbeads

The advantages of vertical microreactor stack with three-dimensional (3D) structure for immunoassay are discussed. The vertical microreactor stack uses vertical fluid flow operation with multifunctional fluid filters. The multi function of fluid filter is very effective for micromixing and passive valve operation. The mechanism of micromixing is discussed by using computational fluid dynamics (CFD), and we know that the mixing mechanism based on Coanda effect. To evaluate the micromixing performance of fluid filter, we demonstrated enzyme reaction with unique repeat mixing operation. As the results, we proved that the fluid filter has very effective mixing performance. The detection limit, which demonstrated by competition enzyme-linked immunosorvent assay (ELISA), is comparable with recommended detection limit, which suggested by Japanese ministry for the environment.     

High efficiency mixing by the use of cross-linked micro capillary fluid filter

A novel type passive mixing device that causes the three-dimensional flow was proposed. This mixer consists of the integrated capillary bundle structure. And the capillaries ware cross-linked each other. So it is called cross-linked micro capillary filter. The mixing effect of the cross-linked micro capillary filter was calculated by the computational fluid dynamics (CFD). The fluid behaviour in the fine three-dimensional structure could be analysed by the use of CFD. In the result of CFD calculation, the cross-linked micro capillary filter estimated high mixing effect. Moreover, the mixing efficiency was become higher by change the cross-linked form. The calculation result was decided the form of the cross-linked micro capillary filter. And this filter was fabricated by application of the Deep X-ray lithography. To form the cross-linked capillary, it was operated twice exposures. In these exposures, respectively the exposure stage was tilted to difference angle. The cross-linked capillary filter fabricated in this way was applied to vertical fluid flow operation. This cross-linked capillary filter could hold and transmit the fluid by the switchover of in impressed pressure. Herewith the cross-linked micro capillary filter showed availability as high efficiency mixing device.     

Simultaneous particle tracking in multi-action motion models with synthesized paths

This paper proposes human motion models of multiple actions for 3D pose tracking. A training pose sequence of each action, such as walking and jogging, is separately recorded by a motion capture system and modeled independently. This independent modeling of action-specific motions allows us 1) to optimize each model in accordance with only its respective motion and 2) to improve the scalability of the models. Unlike existing approaches with similar motion models (e.g. switching dynamical models), our pose tracking method uses the multiple models simultaneously for coping with ambiguous motions. For robust tracking with the multiple models, particle filtering is employed so that particles are distributed simultaneously in the models. Efficient use of the particles can be achieved by locating many particles in the model corresponding to an action that is currently observed. For transferring the particles among the models in quick response to changes in the action, transition paths are synthesized between the different models in order to virtually prepare inter-action motions. Experimental results demonstrate that the proposed models improve accuracy in pose tracking.     

Gaussian process motion graph models for smooth transitions among multiple actions

We propose a unified model for human motion prior with multiple actions. Our model is generated from sample pose sequences of the multiple actions, each of which is recorded from real human motion. The sample sequences are connected to each other by synthesizing a variety of possible transitions among the different actions. For kinematically-realistic transitions, our model integrates nonlinear probabilistic latent modeling of the samples and interpolation-based synthesis of the transition paths. While naive interpolation makes unexpected poses, our model rejects them (1) by searching for smooth and short transition paths by employing the good properties of the observation and latent spaces and (2) by avoiding using samples that unexpectedly synthesize the nonsmooth interpolation. The effectiveness of the model is demonstrated with real data and its application to human pose tracking.