Fabrication of Robust 2-D and 3-D Microfluidic Networks for Lab-on-a-Chip Bioassays

We describe a new method for the fabrication of robust three-dimensional (3-D) lab-on-a-chip devices comprising microfluidic channels and integrated electroanalytical sensors and show their potential application in supporting leak-free pressure driven fluid flow. The technology is based upon the lithographic patterning of a soluble negative photoresist and an insoluble, crosslinked, positive photoresist (SU-8) to produce the pattern of a large area microfluidic network, followed by coating the pattern with silicone rubber or PDMS. After curing, immersion in acetone rapidly elutes the soluble resist to yield the network of channels. As a result the channels formed are robust and it is possible to fabricate a device that supports fluids flowing at high flow rates (without leakage) without the need for special pre-treatment or surface modification of the substrate or silicone covering. We also demonstrate the flexibility of the methodology by producing more complex fluidic networks that comprise bridges which enable one fluid stream to pass over (and remain physically separated from) a second fluid stream. The sealing and packaging techniques, developed for this process do not require the use of extreme conditions and are thus compatible with a broad range of lithographic processes (including, for example, the definition of and incorporation of in situ electrochemical sensor elements). Finally, measurements on a model bioelectroanalytical system applicable to analysis of a model immunoassay are shown, demonstrating the application of this new fabrication method in developing reproducible analytical methods within an encapsulated device.hfillhbox[1297]     

基于模拟退火法的优化线阵的前视三维SAR模型

提出了一种基于模拟退火法的优化线阵的前视三维合成孔径雷达（SAR）模型。针对实线阵需要的阵元个数多、数据计算量大等问题,利用模拟退火法优化3D-SAR的天线阵列得到一个位置优化的非均匀稀疏线阵。分析比较非均匀稀疏线阵和几种不同结构的线阵：非均匀稀疏线阵能以较少的阵元数目达到与其他几种阵列相似甚至更好的波束分辨率,并有效地避免了均匀稀疏阵列的栅瓣问题。分析了前视三维SAR的信号模型。将位置优化的非均匀稀疏线阵应用于前视三维SAR成像并结合BP成像算法。通过仿真实验验证了该模型的正确性和有效性。     

Calibration of a magnetometer array using motion capture equipment

This paper studies the problem of calibrating an array of single‐axis magnetometers in an unknown static inhomogeneous magnetic field using motion capture equipment. A proof of identifiability is given, practical identifiability of calibration parameters is established in simulation, and real world experiments are conducted to demonstrate the feasibility of this approach. Unlike many state of the art techniques, the proposed solution does not require a homogeneous field, as in fact, we demonstrate that an inhomogeneous field enlarges the set of identifiable parameters. Under the above‐mentioned assumptions, this approach may be used to extend self‐calibration techniques of visual‐inertial setups to magnetic sensor arrays in indoor environments.     

A high speed multi-level-parallel array processor for vision chips

This paper proposes a high speed multi-level-parallel array processor for programmable vision chips.This processor includes 2-D pixel-parallel processing element(PE)array and 1-D row-parallel row processor(RP)array.The two arrays both operate in a single-instruction multiple-data(SIMD)fashion and share a common instruction decoder.The sizes of the arrays are scalable according to dedicated applications.In PE array,each PE can communicate not only with its nearest neighbor PEs,but also with the next near neighbor PEs in diagonal directions.This connection can help to speed up local operations in low-level image processing.On the other hand,global operations in mid-level processing are accelerated by the skipping chain and binary boosters in RP array.The array processor was implemented on an FPGA device,and was successfully tested for various algorithms,including real-time face detection based on PPED algorithm.The results show that the image processing speed of proposed processor is much higher than that of the state-of-the-arts digital vision chips.     

Real-time rendering of 3-D scenes using subband 3-D warping

Three techniques for increasing the frame rates of three-dimensional warping, namely subsampling, wavelet baseband, and wavelet transform (including high frequencies) are presented. Additionally noninteger and integer splats are applied for the techniques. The Haar baseband and subsampling methods using integer splats both produce excellent frame rates and perceptual quality of warped images.     

Registration for 3-D point cloud using angular-invariant feature

This paper proposes an angular-invariant feature for 3-D registration procedure to perform reliable selection of point correspondence. The feature is a k-dimensional vector, and each element within the vector is an angle between the normal vector and one of its k nearest neighbors. The angular feature is invariant to scale and rotation transformation, and is applicable for the surface with small curvature. The feature improves the convergence and error without any assumptions about the initial transformation. Besides, no strict sampling strategy is required. Experiments illustrate that the proposed angular-based algorithm is more effective than iterative closest point (ICP) and the curvature-based algorithm.     

3-D curve matching using splines

A machine vision algorithm to find the longest common subcurve of two 3-D curves is presented. The curves are represented by splines fitted through sequences of sample points extracted from dense range data. The approximated 3-D curves are transformed into 1-D numerical strings of rotation and translation invariant shape signatures, based on a multiresolution representation of the curvature and torsion values of the space curves. The shape signature strings are matched using an efficient hashing technique that finds longest matching substrings. The results of the string matching stage are later verified by a robust, least-squares, 3-D curve matching technique, which also recovers the Euclidean transformation between the curves being matched. This algorithm is of average complexity O(n) where n is the number of the sample points on the two curves. The algorithm has applications in assembly and object recognition tasks. Results of assembly experiments are included.     

Self-assembly of 3-D structures using 2-D folding tiles

Natural Computing - Self-assembly is a process which is ubiquitous in natural, especially biological systems. It occurs when groups of relatively simple components spontaneously combine to form...     

3-D pose from 3 points using weak-perspective

This correspondence discusses computing the pose of a model from three matching point pairs under weak-perspective projection. A new approach to the problem that is motivated geometrically is described. Like previous methods, the method here involves solving a biquadratic equation, but here the biquadratic's solutions, comprised of an actual and a false solution, are interpreted graphically. The final equations take a new form, which leads to a simple expression for the image position of any unmatched model point     

Microfluidic reactor array device for massively parallel in situ synthesis of oligonucleotides

We have designed and fabricated a microfluidic reactor array device for massively parallel in situ synthesis of oligonucleotides (oDNA). The device is made of glass anodically bonded to silicon consisting of three level features: microreactors, microchannels and through inlet/outlet holes. Main challenges in the design of this device include preventing diffusion of photogenerated reagents upon activation and achieving uniform reagent flow through thousands of parallel reactors. The device embodies a simple and effective dynamic isolation mechanism which prevents the intermixing of active reagents between discrete microreactors. Depending on the design parameters, it is possible to achieve uniform flow and synthesis reaction in all of the reactors by proper design of the microreactors and the microchannels. We demonstrated the use of this device on a solution-based, light-directed parallel in situ oDNA synthesis. We were able to synthesize long oDNA, up to 120 mers at stepwise yield of 98%. The quality of our microfluidic oDNA microarray including sensitivity, signal noise, specificity, spot variation and accuracy was characterized. Our microfluidic reactor array devices show a great potential for genomics and proteomics researches.     

Microfluidic bioreactors for culture of non-adherent cells

Microfluidic bioreactors (μBR) are becoming increasingly popular for cell culture, sample preparation and analysis in case of routine genetic and clinical diagnostics. We present a novel μBR for non-adherent cells designed to mimic in vivo perfusion of cells based on diffusion of media through a sandwiched membrane. The culture chamber and perfusion chamber are separated by a sandwiched membrane and each chamber has separate inlet/outlets for easy loading/unloading of cells and perfusion of the media. The perfusion of media and exchange of nutrients occur through the sandwiched membrane, which was also verified with simulations. Finally, we present the application of this device for cytogenetic sample preparation, whereby we culture and arrest peripheral T-lymphocytes in metaphase and later fix them in the μBR. The expansion of T-lymphocytes from an unknown patient sample was quantified by means of CFSE staining and subsequent counting in a flow cytometer. To conclude on the applicability of μBR for genetic diagnostics, we prepare chromosome spreads on glass slides from the cultured samples, which is the primary step for metaphase FISH analysis.     

A 2-D microcantilever array for multiplexed biomolecular analysis

An accurate, rapid, and quantitative method for analyzing variety of biomolecules, such as DNA and proteins, is necessary in many biomedical applications and could help address several scientific issues in molecular biology. Recent experiments have shown that when specific biological reactions occur on one surface of a microcantilever beam, the resulting changes in surface stress deflect the cantilever beam. To exploit this phenomenon for high-throughput label-free biomolecular analysis, we have developed a chip containing a two-dimensional (2-D) array of silicon nitride cantilevers with a thin gold coating on one surface. Integration of microfluid cells on the chip allows for individual functionalization of each cantilever of the array, which is designed to respond specifically to a target analyte. An optical system to readout deflections of multiple cantilevers was also developed. The cantilevers exhibited thermomechanical sensitivity with a standard deviation of seven percent, and were found to fall into two categories-those whose deflections tracked each other in response to external stimuli, and those whose did not due to drift. The best performance of two "tracking" cantilevers showed a maximum difference of 4 nm in their deflections. Although "nontracking" cantilevers exhibited large differences in their drift behavior, an upper bound of their time-dependent drift was determined, which could allow for rapid bioassays. Using the differential deflection signal between tracking cantilevers, immobilization of 25mer thiolated single-stranded DNA (ssDNA) on gold surfaces produced repeatable deflections of 80 nm or so on 0.5-/spl mu/m-thick and 200-/spl mu/m-long cantilevers.     

Visual capture and understanding of hand pointing actions in a 3-D environment

We present a nonintrusive system based on computer vision for human-computer interaction in three-dimensional (3-D) environments controlled by hand pointing gestures. Users are allowed to walk around in a room and manipulate information displayed on its walls by using their own hands as pointing devices. Once captured and tracked in real-time using stereo vision, hand pointing gestures are remapped onto the current point of interest, thus reproducing in an advanced interaction scenario the "drag and click" behavior of traditional mice. The system, called PointAt (patent pending), enjoys a careful modeling of both user and optical subsystem, and visual algorithms for self-calibration and adaptation to both user peculiarities and environmental changes. The concluding sections provide an insight into system characteristics, performance, and relevance for real applications.     

Constructing 3-D object models using multiple simulated 2.5-D sketches

Many applications involve the construction of 3-D object models from which images, often requiring a high degree of realism, are later produced. Constructing such models frequently involves considerable human intervention, even in cases where a physical model or the actual object to be modelled exists. This paper describes an approach to the automatic construction of 3-D object models using images of scenes. This method employs a representation of the visible surfaces in a scene called the 2.5-D sketch and a model construction process is described that utilizes multiple simulated 2.5-D sketches.     

3-D object segmentation using ant colonies

3-D object segmentation is an important and challenging topic in computer vision that could be tackled with artificial life models.A Channeler Ant Model (CAM), based on the natural ant capabilities of dealing with 3-D environments through self-organization and emergent behaviours, is proposed.Ant colonies, defined in terms of moving, pheromone laying, reproduction, death and deviating behaviours rules, is able to segment artificially generated objects of different shape, intensity, background.The model depends on few parameters and provides an elegant solution for the segmentation of 3-D structures in noisy environments with unknown range of image intensities: even when there is a partial overlap between the intensity and noise range, it provides a complete segmentation with negligible contamination (i.e., fraction of segmented voxels that do not belong to the object). The CAM is already in use for the automated detection of nodules in lung Computed Tomographies.     

Personal authentication using 3-D finger geometry

In this paper, a biometric authentication system based on measurements of the user's three-dimensional (3-D) hand geometry is proposed. The system relies on a novel real-time and low-cost 3-D sensor that generates a dense range image of the scene. By exploiting 3-D information we are able to limit the constraints usually posed on the environment and the placement of the hand, and this greatly contributes to the unobtrusiveness of the system. Efficient, close to real-time algorithms for hand segmentation, localization and 3-D feature measurement are described and tested on an image database simulating a variety of working conditions. The performance of the system is shown to be similar to state-of-the-art hand geometry authentication techniques but without sacrificing the convenience of the user.