基于MEMS技术的PDMS电泳微芯片的研制

介绍了一种基于MEMS技术的PDM25电泳微芯片，该芯片主要由三部分组成：集成了高压电极的玻璃基底、PDMS薄膜以及刻有微流路的PDMS板。利用lift—off工艺，在玻璃基底上制作了为电泳分离提供高压的Pt电极。为了提高PDMS微芯片的密封效率，同时也为了保持微流路材料的一致性，通过挤压法首先在玻璃基底上形成了一层PDMS薄膜。电泳分离实验表明：在该微芯片上能够实现DNA片段的有效分离。     

MWCNTs based flexible and stretchable strain sensors

Carbon nanotubes have potential applications in flexible and stretchable devices due to their remarkable electromechanical properties. Flexible and stretchable strain sensors of multi-walled carbon nanotubes (MWCNTs) with aligned or random structures were fabricated on poly-dimethylsiloxane (PDMS) substrate with different techniques. It was observed that the spraycoatedtechniquebased strain sensor fabricated on PDMS substrate showed higher sensitivity higher stretchability, better linearity and excellent longer time stability than the sensor fabricated with other methods presented in this work. The scanning electron microscopy images indicated the spray coating technique can produce a better uniform and compact CNT network, which is the important role affecting the performance of CNT-based flexible strain sensors.     

基于蚁群算法的数字微流控芯片并行测试

可靠性是数字微流控生物芯片的一项重要指标,尤其是在安全性要求较高的应用领域。因此,芯片需要在生产制造后或生化实验前进行充分测试,以排除故障,确保实验结果准确。文中针对芯片的结构故障,提出了一种基于蚁群算法的并行测试方案,实现对较大规模的数字微流控芯片进行多液滴并行测试。该方案首先将芯片模型转化为MTSP模型,并利用蚁群算法分布式计算特性搜索多组优化的测试路径,完成对数字微流控芯片实验路径的测试。实验结果表明,该方案可用于在线测试,并能有效地减少大规模芯片的测试时间,且提高了工作效率。     

Simple Method for Fabricating Solid Microlenses With Different Focal Lengths

A versatile method of fabricating different microlenses using a relatively simple process is presented. A liquid-filled lens structure integrated with microfluidic network and liquid Polydimethylsiloxane (PDMS) are used as the frame and filling material, respectively, for the injection process. Through simply changing the injection pressure to obtain different membrane deformation profiles followed by curing, the PDMS stuffing together with the frame will finally form a solid microlens with the corresponding desired focal length. In tests, the fabricated microlenses show good performance in the surface profile and the uniformity between pixels in the array. Focal lengths of microlenses covering a wide range from tens of millimeters to nearly 1.6 mm have also been successfully demonstrated.      

Neural Network Normalization (N3) to Uncover the Differential Signal of cDNA Microarrays

cDNA microarray is a high throughput technology for gene expression analysis. Differing from conventional molecular approaches, which detect molecular targets on a one-by-one basis, cDNA microarray monitors gene expressions of living organisms on a global scale. However, the signal detected by a microarray assay contains a significant amount of noise. Certain types of noise are introduced by the systematic variations that are hardly avoidable by experimental approaches. Significant biological information can only be recognized after the original or raw data sets of microarray assay have been effectively processed. We report here our progress in establishing a Neural Network Normalization (N3) approach to cDNA microarray data processing. With the strong learning ability of the artificial neural network, the trained N3 algorithm is capable of the detection and suppression of systematic variations during microarray data processing and has plasticity in handling both linear and non-linear microarray data sets. The potential of this system in signal processing for other types of biochips, including nucleic acid and non-nucleic acid-based biochips, is yet to be explored.     

Active-Matrix Microelectrode Arrays Integrated With Vertically Aligned Carbon Nanofibers

In this letter, we have successfully integrated vertically aligned carbon nanofibers (VACNFs) onto active matrix thin-film transistor (TFT) and demonstrate a new microelectrode array (MEA) platform. The materials and processes of the bottom gate inverted staggered TFT structure were designed to be compatible with the requisite high-temperature $(sim! hbox{700} ^{circ}hbox{C})$ and direct current plasma-enhanced chemical vapor deposition VACNF growth process. The critical device integration issues are elaborated, and initial device characteristics are reported. This device platform provides great potential as an advanced MEA for direct cell sensing, probing, and recording with a high electrode density and active addressability.      

On-Line Test of Pin-Constrained Digital Microfluidic Biochips with Connect-5 Structure

Digital microfluidic biochips (DMFBs) are widely used in the field of biochemistry. Effective off-line and on-line test for the biochips are required to ensure the system reliability. For direct addressing digital microfluidic biochips (DDMFBs), each control pin corresponds to only one electrode, and that can facilitate the testing of such biochips. However, in pin-constrained digital microfluidic biochips (PDMFBs), multiple electrodes may share one control pin, and thus the testing will be more difficult. In this paper, the pin constraint formula for PDMFBs with connect-5 structure is derived. A novel pin assignment scheme is also proposed, which can conduct on-line test that rarely considered by the previous methods. Furthermore, a hybrid method combining the priority strategy and genetic algorithm is introduced for the on-line test of pin-constrained digital microfluidic biochip with connect-5 structure. The simulation results show that the shortest test path acquired by the proposed method is equal to the optimal value of Euler path, which indicates that the method can effectively implement the on-line test of PDMFBs with connect-5 structure.

     

Highly Flexible Organic Nanofiber Phototransistors Fabricated on a Textile Composite for Wearable Photosensors

Highly flexible organic nanofiber phototransistors are fabricated on a highly flexible poly(ethylene terephthalate) (PET) textile/poly(dimethylsiloxane) (PDMS) composite substrate. Organic nanofibers are obtained by electrospinning, using a mixture of poly(3,3^″′‐didodecylquarterthiophene) (PQT‐12) and poly(ethylene oxide) (PEO) as the semiconducting polymer and processing aid, respectively. PDMS is used as both a buffer layer for flattening the PET textile and a dielectric layer in the bottom‐gate bottom‐contact device configuration. PQT‐12:PEO nanofibers can be well‐aligned on the textile composite substrate by electrospinning onto a rotating drum collector. The nanofiber phototransistors fabricated on the PET/PDMS textile composite substrate show highly stable device performance (on‐current retention up to 82.3 (±6.7)%) under extreme bending conditions, with a bending radius down to 0.75 mm and repeated tests over 1000 cycles, while those prepared on film‐type PET and PDMS‐only substrates exhibit much poorer performances. The photoresponsive behaviors of PQT‐12:PEO nanofiber phototransistors have been investigated under light irradiation with different wavelengths. The maximum photoresponsivity, photocurrent/dark‐current ratio, and external quantum efficiency under blue light illumination were 930 mA W^?1, 2.76, and 246%, respectively. Furthermore, highly flexible 10 × 10 photosensor arrays have been fabricated which are able to detect incident photonic signals with high resolution. The flexible photosensors described herein have high potential for applications as wearable photosensors.     

Flexible Piezoelectric Touch Sensor by Alignment of Lead‐Free Alkaline Niobate Microcubes in PDMS

A highly sensitive, lead‐free, and flexible piezoelectric touch sensor is reported based on composite films of alkaline niobate K_0.485Na_0.485Li_0.03NbO₃ (KNLN) powders aligned in a polydimethylsiloxane (PDMS) matrix. KNLN powder is fabricated by solid‐state sintering and consists of microcubes. The particles are dispersed in uncured PDMS and oriented by application of an oscillating dielectrophoretic alignment field. The dielectric constant of the composite film is almost independent of the microstructure, while upon alignment the piezoelectric charge coefficient increases more than tenfold up to 17 pC N^?1. A quantitative analysis shows that the origin is a reduction of the interparticle distance to under 1.0 µm in the aligned bicontinuous KNLN chains. The temperature stable piezoelectric voltage coefficient exhibits a maximum value of 220 mV m N^?1, at a volume fraction of only 10%. This state‐of‐the‐art value outperforms bulk piezoelectric ceramics and composites with randomly dispersed particles, and is comparable to the values reported for the piezoelectric polymers polyvinylidenefluoride and its random copolymer with trifluoroethylene. Optimized composite films are incorporated in flexible piezoelectric touch sensors. The high sensitivity is analyzed and discussed. As the fabrication technology is straightforward and easy to implement, applications are foreseen in flexible electronics such as wireless sensor networks and biodiagnostics.     

Offline Error Detection in MEDA-Based Digital Microfluidic Biochips Using Oscillation-Based Testing Methodology

Digital microfluidics is an emerging class of lab-on-a-chip system. Reliability is a critical performance parameter as these biochips are employed in various safety-critical biomedical applications. With the introduction of highly scalable, reconfigurable and field programmable Micro-Electrode-Dot-Array (MEDA) architecture, the limitation of conventional DMFBs in varying the droplet size/volume in fine grain manner has been resolved. However, the MEDA-based biochips must be adequately tested upon fabrication to guarantee the correctness of bioassays. In this work, an offline testing approach based on Oscillation-Based Testing (OBT) methodology is presented for MEDA-based digital microfluidic biochips. Various simulations were performed for droplet-electrode short fault model involving single and multiple micro-electrodes. Furthermore, the loss of droplet volume due to the presence of defect was analyzed using COMSOL Multiphysics. The simulation results based on PSpice and COMSOL show that the proposed approach is effective for detecting defects in MEDA-based biochips.     

All Biodisintegratable Hydrogel Biohybrid Neural Interfaces with Synergistic Performances of Microelectrode Array Technologies,Tissue Scaffolding,and Cell Therapy

Biohybrid neural interfaces (BHNIs) are a new class of neuromodulating devices that integrate neural microelectrode arrays (MEAs) and cell transplantation to improve treatment of nerve injuries and disorders. However, current BHNI devices are made from abiotic materials that are usually bio-passive, non-biodisintegratable, or rigid, which restricts encapsulated cell activity and host nerve reconstruction and frequently leads to local tissue inflammation. Herein, the first MEA composed of all disintegratable hydrogel tissue scaffold materials with synergistic performances of tissue conformal adhesiveness, MEA technologies, tissue scaffolding and stem cell therapy on a time scale appropriate for nerve tissue repair is proposed. In particular, the MEA conductive tracks are made from extracellular matrix (ECM)-based double-cross-linked dual-electrically conductive hydrogel (ECH) systems with robust tissue-mimicking chemical/physical properties, electrical conductivity, and an affinity for neural progenitor stem cells. Meanwhile, the MEA hydrogel substrate prepared from transglutaminase-incorporated gelatin/silk precursors simultaneously promotes gelation and interfacial adhesion between all MEA stacks, leading to rapid and scalable device integration. When the full hydrogel MEA is subjected to various mechanical stimuli and moisture, it is structurally stable with a low impedance (4 ± 3 kΩ) comparable to a recently reported benchmark. With seamless lamination around peripheral nerve fibers, the device permits successive neural signal monitoring for wound condition evaluation, while demonstrating synergistic effects of spatiotemporally controlled electrical stimulation and cell transplantation to accelerate restoration of motor function. This BHNI is completely degraded by 1 month thus eliminating the need for surgical retrieval to stably remain, interact, and further fuse with host tissues, successfully exhibiting compatible integration of biology and an implanted electrical system.     

引脚约束的数字微流控生物芯片在线并行测试

随着数字微流控生物芯片在生化领域中的广泛应用,对芯片可靠性和制造成本的要求也越来越高,在线测试对于确保微流控生物芯片正常工作异常重要。该文针对引脚约束的数字微流控生物芯片,提出一种基于改进最大最小蚁群算法的在线并行测试方案,在满足各种约束条件的情况下,采用伪随机比例原则,建立禁忌判断策略,自适应地改变信息素的残留系数,实现引脚约束数字微流控生物芯片的在线并行测试。实验结果表明,该方法可以同时用于离线和在线测试,相对于单液滴离线和在线测试,可有效减少芯片的测试时间,提高了测试工作效率。     

Test Planning in Digital Microfluidic Biochips Using Efficient Eulerization Techniques

Digital microfluidic technology is now being extensively used for implementing a lab-on-a-chip. Microfluidic biochips are often used for safety-critical applications, clinical diagnosis, and for genome analysis. Thus, devising effective and faster testing methodologies to warrant correct operations of these devices after manufacture and during bioassay operations, is very much needed. In this paper, we propose an Euler tour based technique to obtain the route plan of a test droplet for the purpose of structural testing of biochips. The method is applicable to various digital microfluidic biochip architectures, e.g., fully reconfigurable arrays, application specific biochips, pin-constrained irregular geometry biochips, and to defect-tolerant biochips. We show that in general, the optimal Eulerization and subsequent determination of an Euler tour in the graph model of a biochip can be abstracted in terms of the classical Chinese postman problem. The Euler tour can be identified by running the classical Hierholzer’s algorithm, which relies on a simple cycle decomposition and splicing method. This improved Eulerization technique leads to an efficient test plan for the chip. This can also be used in phase-based test planning that yields savings in testing time. The method provides a unified approach towards structural testing and can be easily adopted to design a droplet routing procedure for functional testing of digital microfluidic biochips.     

Hexagonal Network Organization of Dye‐Loaded Zeolite L Crystals by Surface‐Tension Driven Autoassembly

Highly fluorescent dye‐loaded zeolite L crystals, approximately 1.4 μm long and 650 nm in diameter, are organized in a hexagonal network by a surface‐tension‐driven autoassembly process. A polydimethylsiloxane (PDMS) film presenting a trigonal ordering of spherical protuberances, including a polystyrene (PS) hexagonal network occupying their interstices, is chosen as the platform for the assembly. The overall wettability and the difference in surface tension between PDMS and PS surfaces are found to offer good conditions for ordering micrometric dye‐loaded zeolite L crystals in a 2D hexagonal network. The resulting film displays a regular hexagonal pattern of polarized fluorescence, reflecting the polarization properties of the dye molecules inserted in the parallel nanochannels of the zeolites.     

Simple Patterning via Adhesion between a Buffered‐Oxide Etchant‐Treated PDMS Stamp and a SiO2 Substrate

A very simple polydimethylsiloxane (PDMS) pattern‐transfer method is devised, called buffered‐oxide etchant (BOE) printing. The mechanism of pattern transfer is investigated, by considering the strong adhesion between the BOE‐treated PDMS and the SiO₂ substrate. PDMS patterns from a few micrometers to sub‐micrometer size are transferred to the SiO₂ substrate by just pressing a stamp that has been immersed in BOE solution for a few minutes. The patterned PDMS layers work as perfect physical and chemical passivation layers in the fabrication of metal electrodes and V₂O₅ nanowire channels, respectively. Interestingly, a second stamping of the BOE‐treated PDMS on the SiO₂ substrate pre‐patterned with metal as well as PDMS results in a selective transfer of the PDMS patterns only to the bare SiO₂. In this way, the fabrication of a device structure consisting of two Au electrodes and V₂O₅ nanowire network channels is possible; non‐ohmic semiconducting I–V characteristics, which can be modeled by serially connected percolation, are observed.     

Mechanical Gradient Cues for Guided Cell Motility and Control of Cell Behavior on Uniform Substrates

A novel method for the fabrication and the use of simple uniform poly(dimethylsiloxane) PDMS substrates for controlling cell motility by a mechanical gradient is reported. The substrate is fabricated in PDMS using soft lithography and consists of a soft membrane suspended on top of a patterned PDMS substrate. The difference in the gradient stiffness is related to the underlying pattern. It is shown experimentally that these uniform substrates can modulate the response of cell motility, thus enabling patterning on the surfaces with precise cell motility. Because of the uniformity of the substrate, cells can spread equally and a directional movement to stiffer regions is clearly observed. Varying the geometry underlying the membrane, cell patterning and movement can be quantitatively characterized. This procedure is capable of controlling cell motility with high fidelity over large substrate areas. The most significant advance embodied in this method is that it offers the use of mechanical features to control cell adhesion and not topographical or chemical variations, which has not been reported so far. This modulation of the response of cell motility will be useful for the design and fabrication of advanced planar and 3D biological assemblies suitable for applications in the field of biotechnology and for tissue‐engineering purposes.     

基于光学标测技术和MEA技术的植物电研究概述

植物电信号的研究进展很大程度上依赖于测量技术的发展。目前对于微电极等测量技术而言,多方面因素的限制使得同时测量2个以上细胞的电活动基本无法实现,因此对植物群体细胞电活动规律的研究进展较小。本文介绍了2种可以同时对植物群体细胞电活动进行测量并具有空间分辨率的测量技术-依赖于电压敏感染料的光学标测技术和微电极阵列技术。分别介绍了光学标测技术的测量原理、电压敏感染料的特性、系统构成、信号提取方法等内容,并列举了在植物细胞电信号测量方面的应用实例,概述了影响植物电信号光学标测的因素;阐述了微电极阵列技术的系统组成、阵列微电极的特征、测量依据及模型、影响测量的因素,并对阵列微电极在玉米幼根测量中的应用做了简要介绍。最后对这2种测量技术在植物电信号测量中存在的一些问题进行了讨论。     

Shelter Forest Inspired Superhydrophobic Flame-Retardant Composite with Root-Soil Interlocked Micro/Nanostructure Enhanced Mechanical,Physical, and Chemical Durability

The heat accumulation caused by the high power consumption of continuously upgrading electronic devices puts forward more requirements for the adaptability and durability of the flame retardant materials. Herein, inspired by the soil reinforcement effect of the shelter forest roots nearby the river and shoal, a superhydrophobic flame-retardant ethylene-vinyl acetate (EVA)/aluminum trihydroxide (ATH) composite with root-soil interlocked micro/nanostructure (MEA/PGCC) is prepared by combining the micro-extrusion compression molding and spray coating. The homogeneously dispersed ATH and the EVA with sufficient mechanical strength provide durability for the long-term work of the MEA/PGCC composite. The root-soil interlocked micro/nanostructure provides robust superhydrophobicity with a water contact angle of 156 ± 1.0° and a rolling angle of 4 ± 1.0° for the MEA/PGCC composite which is beneficial to improve acid and alkali tolerance, thermic resistance, and de-icing performance. The synergism of interface and surface function prominently improves the flame retardancy of the MEA/PGCC composite, which presents a limit oxygen index of 42%, and remarkable reduction in peak heat release rate of 64%, total heat release of 23%, and peak smoke production rate of 47%. The proposed method is a promising candidate for the mass production and practical application of the superhydrophobic flame retardant composite.     

Zinc Intercalated Lattice Expansion of Ultrafine Platinum–Nickel Oxygen Reduction Catalyst for PEMFC

Platinum (Pt)-based membrane electrode assembly (MEA) catalysts with high performance under operating proton exchange membrane fuel cells (PEMFCs) conditions are a prerequisite for practical applications. As indicated by theoretical calculations, lattice expansion in zinc (Zn)-intercalated Pt alloys can weaken the adsorption of oxygen intermediates, enabling strong electronic interaction for boosting MEA catalysis. To test this hypothesis, herein, a new class of carbon (C)-supported ultrafine Pt alloys with the assistance of Zn is explored. Detailed characterizations indicate that the introduction of Zn can reduce the particle size, and simultaneously intercalates into the Pt alloys, resulting in the lattice expansion for enhancing metallic state of Pt and lowering d-band center. This intercalation strategy can be extended to PtNi, PtCo, as well as Pt. As a result, the optimized Zn-PtNi/C exhibits superior MEA activity (937.6 mW cm⁻² of peak power density), much higher than those of corresponding PtNi/C (771.6 mW cm⁻²) and commercial Pt/C (700.7 mW cm⁻²) under the harsh operating fuel cell conditions. This work opens up a new avenue for creating high-performance PEMFC catalysts in terms of lattice engineering.     

改进的MEA-WNN图像复原方法

模糊图像复原是计算机视觉和图像处理领域的重要任务。针对思维进化算法(mind evolutionary algorithm,MEA)和小波神经网络(wavelet neural network,WNN)相结合的图像复原模型中,MEA的得分函数相对差别小、选优功能较弱等问题,提出了一种改进的MEA-WNN图像复原方法。该方法采用逻辑回归函数进行幂律变换,增加得分之间的差别,从而增强MEA的选优功能。将改进的模型与传统的基于WNN和MEA-WNN的图像复原模型进行对比,改进的模型把复原图像峰值信噪比(peak signal-to-noise ratio,PSNR)分别提高15%和6.5%、结构相似性(structural similarity,SSIM)提高了6.1%和5%,实验结果证明改进模型的有效性和优越性。