Scale Micro Research Articles

Replication of large scale micro pillar array with different diameters by micro injection molding

The capillary force is always used as the driving force of microfluidic chips. In this study, the capillary force of blood smart diagnostic microfluidic chip which fabricated by micro-injection molding (μ-IM) is offered by the structure of micro pillar array. And the detection effect of blood smart diagnostic microfluidic chips is affected by the replication and height distribution of large scale micro pillar array. So the effect of process parameters on the micro-structure and the height distribution of micro pillar is studied. The mold design is also an important factor affecting micro parts properties. In this study, a steel mold insert with almost 15,500 micro blind cavities was fabricated by milling, electrical discharge machine and Femtosecond Laser process. Polymethyl methacrylate -Polystyrene copolymer (SMMA NAS 30) was used as the molding material. The single factor trail and orthogonal experiment approach were adopted to investigate the effect of several process parameters and the significant effect factors affecting the replication of micro pillar. And the height distribution of micro pillar array was investigated by scanning electron microscope (SEM) and universal tool-measuring microscope to measure the replication quality. The results reveal that the replication of micro pillar is sensitive to the flow direction of the polymer melt. The height of micro pillar increases with the increase of mold temperature and injection speed. Moreover, the height distribution of micro pillar along and against flow direction was tightly related to the thermomechanical history of material during the molding process.

The effects of Ag particle morphology on the antireflective properties of silicon textured using Ag-assisted chemical etching

Metal assisted chemical etching (MaCE) of silicon wafers is of interest for fabrication of antireflective layers for single-crystal Si solar cells. This paper presents an Ag-assisted chemical etching approach for single-crystal Si that generates wafer scale micro- and nano-porous textures with controlled surface morphologies and reflectance properties. The approach begins with an Ag thin film annealing process to form Ag micro- and nanoparticles on the Si substrate. This is followed by MaCE, where the Ag particles serve as a catalyst to produce a micro- and nano-porous texture on the Si surface. The morphology of the fabricated Si micro- and nanopores is controlled in accordance with the size and shape of the Ag particles, which are tuned by annealing the Ag films at different temperatures from 300 to 800 °C. The reflectance of the Si surface is in turn determined by the morphology of the etched texture. The fabricated Si antireflective textures have compound hierarchical structures, and an average reflectance of ∼4.7% is obtained when the Ag film is annealed at 600 °C.

Microfluidics and Artificial Blood Vessels as Vascular Prostheses: One Small Step for Vascular Research, One Giant Leap for Patient-Kind

Studies show that in the US alone, approximately 8 million people are affected by Peripheral Vascular Disease and approximately 26.6 million have cardiovascular disease. This report will discuss the usage of lab-on-a-chip devices and artificial blood vessels as vascular prostheses and compare the strengths and weaknesses of the two methods to measure relative efficacy and possible applications in the fields of angiology and cardiology. Lab-ona- chip devices, machines which operate on a liquid scale of micro- or nano-meters and manipulate blood flow and shear stress, may be used as long-term, compact prostheses for smaller blood vessels. Artificial, man-made blood vessels, made either from cells or synthetic material, are become increasingly effective when they are made larger. Both methods may someday be instrumental in saving lives and eliminating vascular disease.

Direct Current Vector Control for Micro-Turbine Distributed Generation System

Direct current vector control technology for micro turbine distributed generation system is the answer to the cost-sensitive applications of power electronics, for both commercial and non-commercial purposes, among all the available energy conversion technologies, permanent magnet synchronous generation combined with a Direct current vector control is most effective because it can operate at variable speeds and can also effectively feed the requirements of the grid, compared to the conventional vector control technologies the direct current vector control has better advantages such as enhanced system stability, reliability and efficiency. In the paper the special features of direct control technologies like fast dynamic response, simple algorithm and reduced sensitivity to parameter variation are discussed. This paper develops two methods for controlling the converter, a new protection method for capacitor over voltage is also evaluated. The interconnection of megawatt scale micro turbine as a set of small modular generation system at the Low voltage distribution level having a significant impact on micro grid performance is also presented in the paper.

Efficient Diffusion Bonding of Large Scale Parts

Worldwide there is a trend to use diffusion bonding for more and more applications, for example for large scale micro channel heat exchangers and heat sinks. For large scaled parts there is only a limited range of systems commercially available today. One most important criterion for large scale diffusion bonding is a homogeneous load distribution. To achieve this, different concepts can be used, e.g. multiple supports around pressing plates or using very thick pressing plates. In the presentation an overview of bonded examples, made of different materials, is given as well as a detailed description of the used diffusion bonding systems. In addition, the methods for characterization of the systems and bonded parts are included as well.

Impact of Microscale and Pilot-Scale Freeze-Drying on Protein Secondary Structures: Sucrose Formulations of Lysozyme and Catalase

Microscale (MS) freeze-drying offers rapid process cycles for early-stage formulation development. The effects of the MS approach on the secondary structures of two model proteins, lysozyme and catalase, were compared with pilot-scale (PS) vial freeze-drying. The secondary structures were assessed by attenuated total reflection Fourier transformed infrared spectroscopy. Formulations were made with increasing sucrose-protein ratios. Freeze-drying protocols involved regular cooling without thermal treatment and annealing with MS and PS equipment, and cooling rate variations with the MS. Principal component analysis of smoothed second-derivative amide I spectra revealed sucrose-protein ratio-dependent shifts toward α-helical structures. Transferability of sucrose-protein formulations from MS to PS vial freeze-drying was evidenced at regular cooling rates. Local differences in protein secondary structures between the bottom and top of sucrose-catalase samples could be detected at the sucrose-catalase ratios of 1 and 2, this being related to the initial filling height and ice crystal morphology. Annealing revealed temperature, protein, formulation, and sample location-dependent effects influencing surface morphology at the top, or causing protein secondary structure perturbation at the bottom. With the MS approach, protein secondary structure differences at different cooling rates could be detected for sucrose-lysozyme samples at the sucrose-lysozyme ratio of 1.

Nano-Scale X-Ray Computed Tomography of Micro-Porous Layers

Recent advances in the development of polymer electrolyte fuel cells have proven that application of a thin micro-porous layer (MPL) on top of the macro-porous fibrous gas diffusion layer (GDL) can significantly enhance the fuel cell performance. Therefore, specific information on the structure of this layer could assist the understanding of the underlying mechanisms. Porosity and pore size distribution (PSD) are the main quantities that reveal important information about the structure. Mercury intrusion porosimetry (MIP) technique has been used previously to characterize the pore phase of the MPL [1]. Focused ion beam integrated with scanning electron microscopy (FIB-SEM) technique is another method of determining the MPL structure, in terms of both solid and pore phases [1,2]. However, these two approaches are generally destructive in nature, and may therefore skew the results by altering the MPL structure either during imaging or during post-processing. In addition, neither method can distinguish between carbon and PTFE inside the MPL [3]. The recent emergence of lab scale micro- and nano-scale X-ray computed tomography facilities provides a new opportunity for obtaining the 3D structure of porous materials by means of a non-destructive approach that can provide high quality images. This approach was used to study the cathode catalyst layer by Nano-scale X-ray computed tomography (NXCT) [4]. The reliability of the approach was assessed by comparing the obtained images by NXCT with transmission electron microscopy (TEM) images [4]. To our knowledge, there is only one published investigation with the focus on MPL imaging using NXCT [5]. In [5], an MPL was used as the sample for comparison of NXCT and FIB-SEM imaging capabilities, and some properties were calculated based on the obtained structures. By increasing the application of NXCT in the field of fuel cell materials, there will be a need for standardized imaging techniques. Hence, the objective of the present work is to develop suitable NXCT imaging, reconstruction, and post-processing protocols for MPLs. For this purpose, commercially available Sigracet SGL 24BC is used as the sample GDL material in this analysis. Two different sample preparation techniques are compared. Furthermore, various algorithms for automatic thresholding of the images are discussed and the most appropriate one for MPL segmentation is recommended. Fig. 1 shows the obtained raw versus segmented image on a cross section of the MPL, for which the porosity is obtained to be 50-52%. Shown in Fig. 2 is also the pore size distribution for the same MPL.MPL thermo-physical properties are also calculated based on the reconstructed images and compared to literature data. Moreover, for the first time, we explore the viability of determining the nanoscale PTFE distribution inside the MPL using the low energy X-ray beam of the Zeiss Xradia 810 Ultra facility. This instrument is considered state-of-the-art for laboratory NXCT and generates a monochromatic X-ray beam with 5.4 keV of energy. The low energy of the X-ray beam provides a good image contrast even for chemical compounds with low effective atomic numbers. Aknowledgment Funding for this research was provided by the Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, and Ballard Power Systems through an Automotive Partnership Canada grant.

Studies on the Reaction of Acrylonitrile Butadiene Styrene to Melt Processing Conditions

Acrylonitrile butadiene styrene (ABS) was investigated for its reaction to melt processing. Studies were done in a lab scale micro extruder and injection molder. It was found that during typical processing times, the ABS begins to undergo a hydrogen abstraction reaction in the presence of oxygen in its polybutadiene (PB) phase. This leads to a crosslinking of the PB chains, which in turn can have an effect on the performance of the polymer. The ABS also was shown to undergo chain scission, opposing the crosslinking effect on the viscosity of the polymer. With higher temperatures, it was found that the crosslinking occurred earlier and at a faster rate. Crosslinking preceded chain scission such that the higher temperatures had the highest peak viscosities. Ultimately, chain scission became the dominant mechanism, decreasing the viscosity. Similar results were seen with changing retention time. Higher retention times in the melt increased the viscosity to a point before decreasing again. During processing, it was found that temperature and shearing both have an effect in progressing the reaction.

Genetic Engineering of Microalgae for Enhanced Biodiesel Production Suitable Fuel Replacement of Fossil Fuel as a Novel Energy Source

Due to negative environmental influence and limited availability, petroleum derived fuels need to be replaced by renewable biofuels. Biodiesel has attracted intensive attention as an important biofuel. Microalgae provide various potential advantages for biodiesel production when compared with ‘traditional’ crops. Specifically, large scale micro algal culture need not compete for arable land, while in theory their productivity is greater. In consequence, there has been resurgence in interest and a proliferation of algae fuel projects. However, while on a theoretical basis, microalgae may produce between 10 and 100 fold more oil per acre, such capacities have not been validated on a commercial scale. There are a series of consecutive processes for biodiesel production with microalgae as feedstock, including selection of adequate micro algal strains, mass culture, cell harvesting, oil extraction and trans esterification. To reduce the overall production cost, technology development and process optimization are necessary. Genetic engineering also plays an important role in manipulating lipid biosynthesis in microalgae. Many approaches, such as sequestering carbon dioxide from industrial plants for the carbon source, using wastewater for the nutrient supply, and maximizing the values of byproducts, have shown a potential for cost reduction. This review provides a brief overview of genetic engineering of microalgae for enhanced biodiesel production.

High speed micro-fabrication using inductively coupled plasma ion source based focused ion beam system

A compact inductively coupled plasma ion source based focused ion beam system (ICP-FIB), capable of producing intense FIB of gaseous elements is developed. Ar and Xe ion beams of 20–4700 nA are focused to spot sizes in the range of 2–30 μm. Experiments using Ar and Xe ion beams of a few microamperes showed milling speeds that are 25–150 times higher than that of a conventional FIB. Milling of micro-apertures in less than 100 s through 100 μm thick Ta and Mo foils and in less than 10 s through 12 μm gold and 25 μm aluminum foils is demonstrated. In this article, the potential of ICP-FIB in high speed milling of micro apertures and large scale micro patterns are presented. Also the possibility of high speed synthesis of nano-pores with tunable pore sizes is discussed.

Triplet Exciton Dynamics in Fluorene−Amine Copolymer Films

Effect of aromaticity on triplet exciton dynamics was studied by transient absorption spectroscopy for two fluorene-based random copolymers with different aromatic amine, poly(9,9′-di-n-octylfluorene-ran-N,N′-bis(4-n-butylphenyl)-N,N′-diphenyl-1,4-benzenediamine) (F8-PDA) and poly(9,9′-di-n-octylfluorene-ran-N,N′-bis(4-t-butylphenyl)-N,N′-diphenyl-9,10-anthracenediamine) (F8-ADA). On a time scale of nanoseconds, triplet exciton was efficiently formed in F8-PDA through the intersystem crossing (ISC) from singlet exciton with a rate constant of 2.0 × 108 s–1. On the other hand, the ISC was not efficient in F8-ADA, resulting in efficient fluorescence emission. On a time scale of micro- to milliseconds, F8-PDA exhibited bimolecular triplet exciton decay due to triplet–triplet annihilation (TTA), but the TTA was negligible in F8-ADA, indicating that triplet excitons can diffuse freely in F8-PDA while they are trapped at ADA units in F8-ADA. The difference in the ISC efficiency and triplet exciton diffusion is ...

The Precision Observation of Projection Model for Microgripper System Based on Stereo Light Microscope

Micro stereovision technology has been widely used in the small scale micro objects which are not convenient observed for human eyes, through micromanipulation and other ways to do image reconstruction for the object surface and show them out in the computer, but during the operation, the precision problem of the position control system and the microgripper system relation to the precision of micro stereovision system. This paper built the camera projection model based on the micro stereovision system and have done lots of displacement experiments of the mobile platform and the gripper reconstruction experiments of microgripper system, through statistical analyzed these experiment data to show the accuracy of the microgripper system.

Small Scale Hybrid Solar Power Plants for Polygeneration in Rural Areas

Small scale micro gas-turbine based hybrid solar power plants are a promising technology for supplying multiple energy services in a controllable and sustainable manner using polygeneration technologies. Compared to a conventional diesel generator based system where electricity is used as the main energy carrier, these systems show great potential to reduce costs and carbon dioxide emissions. Depending on the design, carbon dioxide emissions are reduced by around 9% and equivalent annual costs are reduced by 21% - 26%, as compared to a base polygeneration configuration where cooling services are provided centrally by an absorption chiller without integrating a solar micro gas-turbine. Compared to the system where electricity is used as the main energy carrier a reduction of equivalent annual costs of up to 20% and a reduction of carbon dioxide emissions of up to 33.5% was achieved.

Degradation Modeling Research of Biodegradable Tissue Engineering Scaffold

Although the degradation modeling of tissue engineering scaffold is in its initial step, it can direct the design, optimization of scaffold and help the application in medical case of illness. This paper analyzes the modeling methods and gives the speciality of every model which is put forward by researchers in China and abroad about the degradation of tissue engineering scaffold. These models are divided into micro scale, macro scale and two scale models based on the modeling scales. The recent research is belonging to single scale modeling. Some researchers abroad probed to two scale modeling. The future model is prospected in multi scale coupling macro, micro, and meta-macro model.

The impact of small scale cogeneration on the gas demand at distribution level

Smart grids are often regarded as an important step towards the future energy system. Combined heat and power (CHP) or cogeneration has several advantages in the context of the smart grid, which include the efficient use of primary energy and the reduction of electrical losses through transmission. However, the role of the gas network is often overlooked in this context. Therefore, this work presents an analysis of the impact of a massive implementation of small scale (micro) cogeneration units on the gas demand at distribution level. This work shows that using generic information in the simulations overestimates the impact of CHP. Furthermore, the importance of the thermal storage tank capacity on the impact on the gas demand is shown. Larger storage tanks lead to lower gas demand peaks and hence a lower impact on the gas distribution network. It is also shown that the use of an economically led controller leads to similar results compared to classical heat led control. Finally, it results that a low sell back tariff for electricity increases the impact of cogeneration on the gas demand peak.

Large scale micro finite element analysis of 3D bone poroelasticity

In this paper, a solver for poroelasticity problems related to osteoporotic human bones is discussed. Osteoporosis is a major health problem that compromises the integrity of bones. A good understanding of the disease requires an accurate simulation of the physics. For that purpose, a finite element solver based on Biot's consolidation equations has been developed. A mixed formulation is used to discretize the geometries taken from medical imaging. The resulting indefinite linear systems are solved by Krylov space methods supplemented by variants of Schur complement-based block preconditioners.

Rock Mesoscopic Structural Plane, Mesoscopic Anisotropy and Mesoscopic Anisotropy Index

In this article, we define rock structural planes caused by mineral orientation and layering distribution of some rock ingredients which is different from both rock mass scale structural planes and micro structural plane at crystal scale, as rock mesoscopic structural plane, and the rock anisotropy caused by the existence of these structural planes as rock mesoscopic anisotropy. Rock mesoscopic scale anisotropy index is introduced and its simple but efficient testing method is suggested. With the rock mesoscopic anisotropy index, the degree of rock mesoscopic anisotropy can be quantified easily and the process in simplified.

In vitro Shoot Multiplication of a Seasonal and Vulnerable Medicinal Plant-Aerva lanata L.

The present contribution focused on standardization of in vitro propagation protocols of Aerva lanata, an important medicinal plant used in diverse traditional system of medicine. MS and L2 media supplemented with auxins and cytokinins were used to test the in vitro growth response of explants. L2 media showed positive growth response and complete plant regeneration upon subsequent subculture. Using leaf segments and shoot tips as explants, callusing, shoot multiplication and rhizogenesis were obtained. L2 media fortified with 2, 4-dichlorophenoxyacetic acid (2.5 mg L-1) and benzylaminopurine (1.5 mg L-1) was standardized as the suitable medium for highest number (17 shoots per shoot tip) of shoot production and half strength L2 media with naphthaleneacetic acid (2 mg L-1) for rooting (3.2 cm in 36 days). Hardening of rooted plants was successful on 1:1:1 ratio of Soil rite:Coco peat:Vermiculite, later plants were transferred to pots containing sterile soil and maintained in Green house then planted in the field. The survival rate was between 65 and 70. The method established could be adopted for rapid large scale micro propagation and conservation of this important vulnerable medicinal herb. © 2011 Asian Network for Scientific Information.

Fabrication of superhydrophobic surface by hierarchical growth of lotus-leaf-like boehmite on aluminum foil

Hierarchical growth of boehmite film on the aluminum foil was carried out via a facile solution-phase synthesis route. The resultant film is composed of three-dimensional microprotrusions assembled from well aligned nanoneedles. Such dual scale micro-/nanostructures are highly similar with those of lotus leaves. The resultant surface after hydrophobization exhibits a water contact angle of 169° and a sliding angle of ∼4° for a 5 μL droplet, which is ascribed to the combination of the dual scale roughness at the micro- and nanometer scale and the low surface energy of stearic acid coating. The obtained film possesses relatively good adhesion to the aluminum substrate and keeps superhydrophobicity after the ultrasonic treatment or long-term storage in spite of the partial loss of it superhydrophobic ability after abrasion test.

An Autonomous Micro Robot Fish Based on IPMC Actuator

The structure and control system of micro robot fish are designed based on the properties of the IPMC (ionic polymer metal composite) after analyzing locomotion and force of small fish. Then efficiency improvement of the IPMC is discussed, and various locomotion patterns are realized on the micro robot fish. The experimental results prove that an IPMC based centimeter scale micro robot fish is feasible. The velocity control can be realized by changing frequency and duty ratio of the control signal, and ascent-descent, turning, cruising can be realized by the cooperation of pectoral fin and caudal fin. Finally, this paper analyzes how to improve propulsive efficiency from the viewpoint of structure design of the caudal fin propulsor.