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Membraneless microfluidic enzymatic biofuel cells (μEBFCs) operated under the co-laminar flow of fuel and oxidant often face cross-mixing issues, especially at low flow rates. In this work, we propose a new approach to design the single-stream μEBFC based on the investigation of relative positions of the electrodes at the top and bottom of the microchannel. To achieve this, a μEBFC was fabricated with multiwalled carbon nanotube (MWCNT) electrodes via a stencil method. The bioanode and biocathode were modified with glucose dehydrogenase and laccase via direct covalent bonding, respectively. The best results were attained by placing the cathode at the top and anode at the bottom of the microchannel in a Y-shaped two streamflow μEBFC. When a single electrolyte stream was used to achieve more practicality and ease of use, the performance was reduced by 40%. However, with the new design of electrodes in single-stream μEBFC, i.e. cathode at the top and anode at the bottom facing each other in the microchannel, the performance was recovered by 20%. This corresponds to maximum current and power density of 216 ± 12 μA cm−2 and 69.2 ± 9.2 μW cm−2, respectively. The stacking ability of the device was realized by connecting the two cells in series and parallel. The maximum power density delivered by the two single-stream μEBFCs’ stack reached 160 μW cm−2 at 0.3 V. Thus, this study validates the viability of using single-stream μEBFCs in large stacks to power microelectronics more simply and practically.

We present a parallel microfluidic array chip for the fast preparation of microdroplets to provide droplet arrays of a sample using the hydrodynamics of immiscible fluids as they flow in a microchamber and bypass channel. The microfluidic chip has eight channels that are parallel from the inlet to the outlet of the device. Each channel has 13 microchambers and bypass channels to trap the droplets from the sample plugs. Because samples can be arrayed simultaneously in eight parallel channels, the arrays of sample droplets can form quickly. After filling the microchannel and chambers with the sample, oil is injected into the device. As the oil fills the microchannel, owing to the difference in the flow resistance between the microchamber and bypass channel, the oil flows through the bypass channel, trapping the sample in the microchamber. A total of 104 microdroplets of an aqueous sample could be successfully trapped in 8 x 13 arrays of microchambers using one simple injection of sequential plugs of mineral oil, the aqueous sample, and mineral oil with surfactant. Sample droplets were successfully formed at all chambers at flow rates of less than 0.06 mL/h, and a trapping efficiency of greater than 90% was achieved at 0.15 mL/h.

Exoskeleton robots are used to augment human power to perform difficult tasks. These robots can generate eternal load on human muscles as training devices. In this paper, a lower-limb training device using exoskeleton is developed for muscle power augmentation during cyclic motion. A control system determines augmenting power on the human leg during pedaling motion based on the calculation of muscle activity timing. The resulting power of the exoskeleton assists cycling motion as a rehabilitation system or applies mechanical load on the leg muscles as a training system. Measurement of interaction force by the load cell on each pedal determines admittance control signal. Experiments to assist bicycle riding motion using the developed exoskeleton were conducted. From the interaction force analysis, the sources of errors in the motion control are found, and the application-specific problems are discussed. Given that the exoskeleton robot can control hip and knee joint independently, the proposed system can be extended for assisting various motions in daily life, including walking rehabilitation.

Fuel cell is an efficient energy conversion device converting chemical energy directly into electrical energy. It is a fact that, to boost the fuel cell performance, resistance (charge transfer resistance, mass transfer resistance and electrolyte resistance) should be decreased. For this, many techniques have been used for cell testing such as: cyclic voltammetry, current interruption measurement, chronoamperometry, chronopotentiometry, polarization curve and electrochemical impedance spectroscopy (EIS). Among these techniques, EIS is a well-established, non-intrusive, non-destructive, semi-quantitative, and an efficient technique for identification of each circuit element. In this review article, application of electrochemical impedance spectroscopy in identification of individual components of total resistance and their dependence on different factors in biofuel cell along with some recent advancement in this technique have been discussed.

Cisplatin is the most effective and widely used chemotherapeutic agent for many types of cancer. Unfortunately, its clinical use is limited by its adverse effects, notably bone marrow suppression leading to abnormal hematopoiesis. We previously revealed that neuropeptide Y (NPY) is responsible for the maintenance of hematopoietic stem cell (HSC) function by protecting the sympathetic nervous system (SNS) fibers survival from chemotherapy-induced bone marrow impairment. Here, we show the NPY-mediated protective effect against bone marrow dysfunction due to cisplatin in an ovarian cancer mouse model. During chemotherapy, NPY mitigates reduction in HSC abundance and destruction of SNS fibers in the bone marrow without blocking the anticancer efficacy of cisplatin, and it results in the restoration of blood cells and amelioration of sensory neuropathy. Therefore, these results suggest that NPY can be used as a potentially effective agent to improve bone marrow dysfunction during cisplatinbased cancer therapy. [BMB Reports 2017; 50(8): 417-422].

The manufacture of helical pinion gears has involved machining processes such as hobbing and shaving to achieve the required dimensional accuracy. However, these conventional processes have some disadvantages such as excessive material loss, low productivity, high-energy consumption, and high carbon emissions. To overcome these problems, a cold extrusion process is applied to the manufacture of helical gears. In this study, we analyze the environmental effects of the cold extrusion process, designed for the sustainable production of helical gears. We quantitatively analyze the environmental effects of the conventional machining and cold extrusion processes, using the Life Cycle Assessment technique in accordance with ISO 14000. This analysis includes the energy consumption and carbon emissions for a helical gear manufactured using the conventional machining processes and those of single- and double-type gears manufactured using the cold extrusion process. Moreover, the material properties of the extruded helical gears are compared with the conventionally machined gears. In conclusion, the extruded gears exhibited a higher strength while consuming less energy during their manufacture than the gears manufactured using the conventional machining processes. Further, this alternative process is more cost effective as it generates less waste and exhibits high productivity compared to the conventional machining processes.

We present a 512-microchannel geometrical passive breakup device for the mass production of microdroplets. The mass production is achieved through the passive breakup of a droplet into two droplets. The microchannel geometry in the microfluidic device was designed and optimized by focusing on stable droplet splitting for microdroplet preparation and minimizing the hydraulic resistance of the microchannel for achieving high throughput, the minimization of hydraulic resistance was achieved by employing analytical approaches. A total of 512 microdroplets could be prepared from a single liquid plug by making the liquid plug pass through nine sequential T-junctions in the microfluidic device, which led to the splitting of droplets. The microfluidic device was fabricated using conventional photolithography and polydimethylsiloxane (PDMS) casting. We estimated the performance of the microfluidic device in terms of the size distribution and production rate of microdroplets. Microdroplets with a diameter of 40.0 &plusmn, 2.2 &micro, m were prepared with a narrow size distribution (coefficient of variation (CV) &lt, 5.5%) for flow rates of disperse (Qd) and continuous phase (Qc) of 2 and 3 mL/h, respectively. Microdroplet production rates were measured using a high-speed camera. Furthermore, monodisperse microdroplets were prepared at 42.7 kHz for Qd and Qc of 7 and 15 mL/h, respectively. Finally, the feasibility of the fabricated microfluidic device was verified by using it to prepare biodegradable chitosan microspheres.

The original version of this article unfortunately contains a mistake. The acknowledgement section of the above article is incorrect. The correct acknowledgements are as follows

A light scanning device with two microfluidic hemicylindrical lenses was demonstrated for adjustable laser sheet beam scanning applications. An elastomeric hemicylindrical lens, whose focal length can be adjusted by control of the applied fluidic pressure, was fabricated by application of the pressurized casting process on polydimethylsiloxane (PDMS) obtained from a prepared microsized mold. The hemicylindrical lens consisted of a thin membrane, a liquid chamber and a microchannel. The applied fluidic pressure deformed the lens membrane and changed the lens shape. The change of the lens shape allowed beam shape transformation or beam scanning according to the relative size of the beam to the lens. By orthogonally placing two microfluidic lenses of different sizes, 1 mm × 5 mm and 3 mm × 15 mm, respectively, a spot laser beam from a 200μm-large pinhole was transformed into laser sheet, and then the laser sheet was scanned. The relationship between the lens properties, including lens curvature and laser beam shaping according to different applied pressures on the lens, were systematically investigated. Laser beam scanning properties of the microfluidic light scanning device were also characterized for various applied pressures and offset distances.

In the present study, we experimentally investigated the roll stability recovery performance of a vehicle at various tilting angles. The vehicle was ultimately targeted to contain a velocity-field measurement system in underwater conditions, which should confirm stationary buoyancy during measurement. We employed two small gear-rack ax mountings on a weighted mass as the actuating system inside the bluff-body. Speed and movement were feedback controlled by the activating electronic motor system. The feedback algorithm used tilting action signals from an inclinometer sensor installed in the central region of the vessel shell. As a result, the bluff-body vessel effectively recovered self-stabilizing positions against the tilting action.

In the present study, we measured velocity vector fields in a vertical section behind a swirl generator structure using an ultrasound particle image velocimetry (PIV) method. The ultrasound transducer was employed as an illumination beam source to have the advantages in measuring the vertical section of the flow wake in a circulating water channel. The frequencies of the ultrasonic imaging system were in the range of 35-50 MHz and the focal depth was 12 mm from a probe. The field of view was about 4 mm x 13.5 mm. We were able to observe the instantaneous wake flow structure using an ultrasound image by applying the PIV algorithm.

We measured experimentally the properties of fluid dynamics, velocity fields, and the pressure, around stenotic obstruction located inside a circular channel structure. Particle image velocimetry system was employed to obtain velocity fields at the central section of the circular channel in the streamwise direction. The stenosis model used was made of acrylic material with different stenotic aspect ratios. The working fluid was water and it was returned by a centrifugal pump system. Pressure measurements were carried out to validate the effect of a narrow passageway. Results showed that the acceleration of gap flow through stenotic obstruction and the pressure drop in the recirculation regime behind the stenosis model can be observed.

A direct patterning for a barrier rib using the roll-imprinting process is getting more interests in display manufacturing fields. Master roll patterning is one of the important issues in the roll-imprinting process. In this study, a novel fabrication process of micro-patterning on a roller surface by applying the photolithography process is studied. Because the roller surface was a cylindrical shape, the designed pattern was made by using a film mask. Special jigs and roll holder were designed and used for the photolithography on the roll substrate. The roll patterning results showed a feasibility of the proposed method for the photolithography on the roll’s surface.

We present a novel microvalve for the treatment of a pathological condition, i.e., hydrocephalus. This microvalve is made of polydimethylsiloxane/Parylene composite layer which has a 3-D dome petal shape. This geometry enables the microvalve to rectify fluid flow in the forward and backward directions. New microfabrication techniques such as dome-shaped SU-8 mold fabrication and excimer laser machining for valve opening have been investigated to build the proposed microvalve. The pressure drop versus flow rate characteristics of the fabricated microvalve was investigated through in vitro flow tests. The flow test results showed that a 10 × 10 microvalve array with a cross-cut opening shape (200 × 60 μm) was found to be optimal for the treatment of hydrocephalus.

A method for fabrication of flexible stencil was studied. Flexibility of the stencil allows micropatterning on a curved surface by material deposition or material removal (etching) through patterned hole of the stencil. In this study, low mechanical stability of the thin stencil membrane was improved by bonding the membrane with rim supporter which is thick and strong enough for easy handling of the stencil. Both of the membrane and rim structure were made of elastomer, PDMS using molding process from SU-8 master mold. The application test of shadow deposition and etching on underlying nonplanar surface using the fabricated flexible stencil mask showed the feasibility of the suggested technique into micro- patterning on a curved surface.

In micro electrochemical machining(micro-ECM), it is important to measure and control the potential of a tool electrode and a workpiece electrode because electrochemical reaction rate depends on the potential of the electrodes. When the electrode potential was measured against a reference electrode, the error of measured electrode potential could be minimized by proper tool electrode design. In this paper, multi-function electrodes consisting of a tool electrode and a reference electrode was fabricated by micro fabrication techniques. The machining conditions in micro-ECM using multi-function electrodes, such as pulse voltage parameters and electrode potential, were investigated.

We report the results of diffuser lithography applied to a negative-type thick photoresist to fabricate 3-dimensional microstructures suspended on supports. When UV light passes through a diffuser film, the direction of the light is randomized because of the irregular surface of the diffuser. By exposing through a diffuser on a Cr-mask, a circular or an elliptical cross-section of exposed region can be formed on a spin-coated photoresist. When applied to a negative-type thick photoresist, diffuser lithography gives a 3-dimensional circular cross-section of the exposed and cross-linked regions, which could be used for making suspended microstructures. The size of the exposed region has been controlled by the dose of the UV light. The current study clearly shows that the depth of exposed region of photoresist is affected by the geometry of the pattern. By controlling the depth of the exposed region using different pattern size, beam structures suspended on the support structures could be fabricated by single exposure process. The characteristics of the diffuser lithography process were investigated on a negative type photopolymer, SU-8, with different doses of UV-light and different geometry.

The biological flow characteristics inside a microchannel were investigated experimentally using a micro-particle image velocimetry (micro-PIV) method. The main objectives of this study were to understand the blood flow in micro-domain blood vessels and to identify the feasibility of nano-scale fluorescent particles for velocity measurement. The flow field was analyzed with a spatial resolution of 1 K ×1 K pixels at low Reynolds number flow. To obtain the spatial distributions of mean velocity, 100 instantaneous velocity fields were captured and ensemble-averaged. As a result, for the case of blood flow, there were substantial velocity variations in the central region of micro-channel due to the presence of blood cells in the blood flow.

A new method to fabricate microfluidic channel which has metal electrodes on side wall is presented. Three dimensional electrode patterns were deposited through the shadow mask on highly recessed surfaces of microchannel. Polymer microchannel was fabricated using polymer molding technique. Shadow mask for electrode patterning were fabricated using MEMS process. Electrodes were patterned on side wall of microchannel using shadow effects occurring at angled evaporation through shadow mask. The electrodes on side walls facing each other are expected to provide more sensitivity at bio-analysis devices based on impedance variation.

In this paper, a new method is proposed to predict mean cutting force in ball-end milling of sculptured surfaces. The cutter contact area, which is obtained from Z-map of the hemispherical part of the cutter, is expressed as a set of grids on the cutter plane orthogonal to the cutter axis. Before calculation of cutting force, cutting force density in each grid is calculated using empirical cutting parameters. The calculated force density corresponding to the grid position on the cutter plane is defined as a force map. The mean cutting force in an arbitrary cutter contact area is easily calculated by summing up the cutting force densities of the engaged grids in the force map. The proposed method was verified through the slotting and slanted surface machining by varying the surface inclination angle. From the experimental results, it was shown that mean cutting force can be calculated accurately and fast.

A rapid and simple method to fabricate tiny shadow-masks and their use in multi-layer surface patterning with in situ micromechanical alignment is presented. Instead of using silicon micromachining with through-wafer etching to define the thin membrane with etched apertures, we are using photoplastic SU-8-based resist as structural material of both membrane and support rim. Two layers, 5 and 150 μm thick, are structured by lithography and finally released from the surface. The free-standing SU-8 membranes have apertures ranging from 6 to 300 μm. They are placed and mechanically fixed to the surface, which needs to be patterned. Deposition by evaporation of Cr, Au, Al or other material through the membrane apertures results in an accurate 1:1 replication of the aperture pattern. In view of multi-layer patterning, we used in situ micromechanical alignment pins or jigs and achieved an overlay precision of

This paper presents a method to analyze the 3-dimensional form error of a ball-end milled surface due to the elastic compliance of the cutting tool. In order to estimate the form error in various cutting modes, the cutting force and the cutter deflection models including the effect of the surface inclination were established. The cutting forces were calculated by using the cutter contact area determined from the Z-map of the surface geometry and the current cutter location. The tool deflection responding to the cutting force was then calculated by considering the cutter and the holder stiffness. The cutter was modeled as a cantilever beam consisting of the shank and the flute. The stiffness of the holder was measured experimentally. Various experimental works have been performed to verify the validity of the proposed model. It is shown that the proposed method is capable of accurate prediction of cutting forces and the surface form error.

The cutting force in ball-end milling of sculptured surfaces is calculated. In sculptured surface machining, a simple method to determine the cutter contact area is necessary since cutting geometry is complicated and cutter contact area changes continuously. In this study, the cutter contact area is determined from the Z-map of the surface geometry and current cutter location. To determine cutting edge element engagement, the cutting edge elements are projected onto the cutter plane normal to the Z-axis and compared with the cutter contact area obtained from the Z-map. Cutting forces acting on the engaged cutting edge elements are calculated using an empirical method. Empirical cutting mechanism parameters are set as functions of cutting edge element position angle in order to consider the cutting action variation along the cutting edge. The relationship between undeformed chip geometry and the cutter feed inclination angle is also analyzed. The resultant cutting force is calculated by numerical integration of cutting forces acting on the engaged cutting edge elements. A series of experiments were performed to verify the proposed cutting force estimation model. It is shown that the proposed method predicts cutting force effectively for any geometry including sculptured surfaces with cusp marks and a hole.

Haptic is a tactile feedback technology which has the advantage of the sense of touch by applying forces, vibrations or motions to the user. To use the haptic device for remote control, it is need to sense the object. These sensors are called as haptic sensor, and it senses the magnitude, direction, and distribution of a force. The sensed force data are used to reproduce the boundary limit of remote user's movement or the reactions from objects. We develop an elastic material based tactile sensor for sensing the reaction force and the shape of contact surface. Sensor surface is made of Poly-dimethylsiloxane(PDMS) and it has small patterns with chrome. The deformation of these patterns is calculated by computer vision. By this process we could know the amount force that gave from some object. We performed the experiment with force sensor to find the relationship between the force and deformation of surface.

The biological flow characteristics inside a rugged surface type microchannel are investigated experimentally using a micro-particle image velocimetry (micro-PIV) method. The main objectives of this study are to understand the blood flow structure inside a micro-domain blood vessel and to identify the feasibility of nano-scale fluorescent particles for velocity field measurement in a micron-sized channel. The flow field is analyzed with a spatial resolution of 1K×1K pixels at low Reynolds number flow. To obtain the spatial distributions of mean velocity, 100 instantaneous velocity fields are captured and ensemble-averaged. As a result, for the case of blood flow, there are substantial cell deformation and variations to pass through the rugged surface of a microchannel and the clear velocity vector field was acquired by using the present micro-PIV technique.

A wide range of applications in neurotechnological research rely on planar microelectrode arrays (MEA) but the disadvantage of these systems is the low density of electrodes caused by the problem of wiring a great number of electrodes. In turn this results in a low number of good cell to electrode contacts. To overcome this drawback, a great number of laterally isolated sub-μm electrodes is placed on a photoconductor layer (amorphous silicon a-Si:H). By use of a laser beam, only those sub-μm electrodes lying under the cell can be selected to form an electrical contact to one of the underlying indium tin oxide (ITO) leads providing a high seal resistance at the cell/electrodes interface. A biocompatible and biostable composite layer of electrodes (100–500 nm) and insulator is formed using nanostencil-technology. Dark to bright ratio D of the photoconductor is determined to 105–106. The impedance of Au and TiN sub-μm electrodes in physiological solution is measured. Spatial resolution of the system is limited by light-scattering inside the supporting glass substrate; the effective diameter of the conductive region illuminated by the laser spot with intrinsic diameter 1.6 μm is ~6–7 μm.

A rapid and simple fabrication method to construct tiny shadow-masks and their use in multi-layer surface patterning with in-situ micromechanical alignment is presented. Free-standing shadow-mask membranes are made of a 5-µm-thick SU-8 based resist layer by photolithography. They are supported by a 1-mm-large and 150-µm-thick SU-8 rim. The membrane has apertures with feature sizes ranging from 6–300 µm. Multiple layer deposition by electron beam evaporation of Cr, Au and Al through the membrane apertures results in aligned multilayer patterns. By using in-situ micromechanical alignment pins or jigs we achieved an overlay precision of < 2 µm in both, x and y direction. The resistless shadow mask deposition technique eliminates photolithography processes and allows surface patterns to be made in a rapid and vacuum-clean way on arbitrary millimeter-size surfaces, and at low-cost.

An elastomeric microfluidic lens of variable focal length was fabricated by single casting from a microfabricated mold. The lens is a poly(dimethylsiloxane) (PDMS) microfluidic chamber covered with a thin membrane. By introducing fluid inside, the pressure varied in the microfluidic chamber, which produced a shift in the microlens focal plane resulting in a change in the back focal length of the lens. Hot pressing was used to fabricate the microfluidic chamber and membrane in a single body. The fabrication processes are simple, avoid handling difficulties of the thin membrane, and provide uniform thickness of the membrane, which essentially affect lens performance. The optical properties of the lens such as lens shape, back focal length, and numerical aperture were calculated and measured at various lens geometries and applied pressures. The back focal length of the lens changed approximately from 30 to 5 mm. The relationships of the optical properties, namely, back focal length and numerical aperture, with applied pressure were studied and verified using optical image tests. The variable focal length of the microfluidic lens is critical to increase the efficiency of light detection in optical or biophotonic applications.

A means of accurate control of the curvature radius of molds that are used in nanostructure replication techniques is presented. The local non-uniform growth of SiO2 at regions with high curvature is used to fabricate molds with a curvature radius ranging anywhere between 10 and 250 nm. The mold radius is predicted by numerical simulation as a function of oxidation temperature and time and confirmed by a series of oxidation and etching experiments. The silicon, silicon dioxide, and polymer nanostructures are analyzed by scanning electron microscopy and compared with the theory. Replication into photo-plastic polymer from various sharp and round molds is performed, and their properties are discussed. Our results are useful for designing nanostructures in the area of soft lithography and nanoprobe engineering.