Microgroove Arrays Research Articles

A hybrid process of raining co-deposition and rotary wire spark erosion in the development of a custom CBN tool for making a biochip injection mold

This study examines a hybrid process combining raining co-deposition and rotary wire spark erosion with one-off grinding to generate an array of microgrooves in the fabrication of biochip injection molds on NAK80 steel. A precision composite electroforming device that can create a rain like co-deposition effect to uniformly grow a Ni-based Cubic Boron Nitride (CBN) abrasive layer onto a wheel-blank substrate is proposed and employed. Slicing and dressing are conducted by using rotary wire spark erosion to make the co-deposited wheel-blank into a thin CBN wheel-tool with a grinding edge array that alternates between coarse and detailed. A multiple microgroove array on NAK80 steel is one-off generated by using the developed CBN wheel-tool array, swiftly creating a superior surface finish for biochip injection molding. A comprehensive examination of the quantitative and qualitative properties of the CBN wheel-tool was undertaken. Experimental results have been evaluated in terms of CBN grit content, accuracy of co-shaft machining, influence of grinding depth, shape of microgroove and tool wear as well as an estimation criterion for the CBN wheel-tool array.

A measurement method of cutting tool position for relay fabrication of microstructured surface

By using the secondary function of a force sensor integrated fast tool servo (FTS) for surface profile measurement, the three-dimensional tip position of a micro-cutting tool in the FTS with respect to the fabricated microstructures was measured without using any additional instrument for realizing the concept of relay fabrication of microstructured surface. It was verified from the experiments for testing the basic performances of tool tip position measurement that the delay of the force feedback control loop of the FTS was a big factor influencing the position measurement accuracy. A bidirectional scanning strategy was then employed to reduce the position measurement error due to the delay of the feedback control loop. Tool tip position measurement experiments by using micro-tools with a nose radius of 100 µm for relay fabrications with sub-micrometer accuracies, including stitching fabrication of a micro-groove line array and filling fabrication of a microlens lattice pattern, were carried out to demonstrate the feasibility of the tool position measurement method.

Performance Evaluation of Lubricant for Producing Smooth Surface Product in Cold Extrusion of Aluminum Using Tool with Micro-groove Arrays

The effects of lubricating oil on surface quality of the extruded aluminum product were investigated by carrying out a series of plane strain cold extrusion experiments. The forming dies of extrusion apparatus were assembled with a combination of the taper die and the plane plate tool with the micro-groove arrays formed on its surface. Four lubricants were tested by using the above apparatus. Then, adhesion of aluminum billet to the surface section of the plane plate tool on which the micro-groove arrays were formed, surface roughness of the billet after passing through the above section of the plane plate tool and surface conditions of the billet and tool at the die bearing section of a tool were investigated, and performance evaluation of lubricant for producing smooth surface product could be carried out successfully.

Precision grinding of optical glass with laser micro-structured coarse-grained diamond wheels

This paper presents a series of micro-structured coarse-grained diamond wheels for optical glass surface grinding aiming to improve the grinding performance, especially subsurface damage. The 150μm grit size, single layer electroplated diamond grinding wheels with different interval micro-groove arrays were manufactured by nanosecond pulsed laser, successfully. The influence of micro-structures on surface roughness and subsurface damage was investigated. Compared with conventional coarse-grained diamond wheel, the subsurface damage depth was reduced effectually from 5 to 1.5μm, although the better surface roughness was not obtained by the micro-structured coarse-grained diamond wheel. In addition, the surface roughness and subsurface damage depth were both reduced with the decreasing interval of micro-groove arrays.

Directional Oil Sliding Surfaces with Hierarchical Anisotropic Groove Microstructures

A robust directional oil sliding surface is presented by utilizing re-entrant micro-groove arrays inspired from the microgrooves of rice leaf. The overhang micro-groove arrays are shown to provide two primary goals of "omniphobicty" and "anisotropic sliding" with DI water (γlv = 72.1 mN/m) as well as mineral oil (γlv = 28 mN/m) and conventional photoresist.

Femtosecond laser surface structuring technique for making human enamel and dentin surfaces superwetting

It is known that good wettability of enamel and dentin surfaces is a key factor in enhancing adhesion of restorative materials in dentistry. Here, we report on a femtosecond laser surface texturing approach that makes both the enamel and dentine surfaces superwetting. In contrast to the traditional chemical etching that yields random surface structures, this new approach produces engineered surface structures. The surface structure engineered and tested here is an array of femtosecond laser-produced parallel microgrooves that generates a strong capillary force. Due to the powerful capillary action, water is rapidly sucked into this engineered surface structure and spreads even on a vertical surface.

Ultra-Precision Flycutting Microstructures on Brittle Materials

Ultra-precision microstructures on brittle materials are critical components in optical communication industry. The requirements for Ultra-precision microstructures manufacturing are increasing recently. Traditional etching and deposition technology can not satisfy the demands of accuracy and efficiency. Ultra-precision flycutting process is presented to machining microstructures on brittle materials. The geometric model of flycutting is analyzed. A formula is established to describe the relationship between the effective cutting depth and cutting parameters. The critical depth for brittle to ductile transition is obtained by cutting experiments with varying cutting depth on quartz glass. The ductile cutting chips are achieved in fly-cutting process. A microgroove array with optical quality is obtained. It proves that ultra-precision flycutting process is an available method to manufacture microstructures with optical quality on brittle materials.

A002 Development of A High-Precision Hybrid CNC Machine Tool for In-Situ Fabricating A Biomedical-Slide Mold

The study presents a novel approach to the fabrication of a biomedical-slide mold for in-situ producing convex platform quantitative cell-counting slides made of PMMA. The process incorporates three important procedures: 1) the development of a high-precision hybrid dual-spindle CNC machine tool; 2) the formation of a boron-doped polycrystalline composite diamond (BD-PCD) wheel-tool on the machine tool developed; and 3) the cutting of a multi-groove -biomedical-slide mold array using the formed diamond wheel-tool in-situ on the developed machines. The factors influencing formation of the wheel-tool and generation of the microgroove array are discussed in detail.

Micro and Precision Grinding Technique and Functional Behavior Development of Micro-structured Surfaces

Due to the difficult control of machined micro-structured form-accuracy of hard and brittle materials such as monocrystalline silicon, optical glass and so on, a micro-grinding is developed. It utilizes the micro-tip shape of diamond wheel and the micro-grit cutting-edges on its working surface to machine the micro-groove array on hard and brittle material surface. To explore its function behaviors, it is applied to the substrate surfaces of thin film solar cell, silicon chip and graphite blades, their photovoltaic properties, wettability and pump efficiency are measured and investigated, respectively. The machining results show that the micro-grinding may produce an accurate and smooth micro-structured surface. The applications show that the thin film solar cell with micro-lens structured substrate exhibits higher conversion efficiency and fill factor in weak light and scattered light, thus it may be used to make electricity without solar irradiation. When the silicon surface is machined to be a micro-grooved structure, an increase in micro-groove depth leads to an increase in the contact angle of droplet, and gradient micro-grooved surface may drive the micro-motion of droplet. In oil pump, when the micro-grooved depth is decreased from 500 μm to 100 μm in the case of micro-grooved graphite blades, the work efficiency is increased gradually, finally greater than the traditional one. Therefore, the accurate and smooth micro-structured surface may produce high value-added functions.

Micro-grinding of micro-groove array on tool rake surface for dry cutting of titanium alloy

A micro-grinding approach is proposed to fabricate micro-groove array on tool rake surface. These micro-grooves were used to rapidly dissipate cutting chips and heat from cutting zone for eco-cutting of titanium alloy without any coolant. This tool is called micro-grooved tool. The objective is to replace chemical and high-energy-beam etching approaches because they have not yet been able to control micron-scale groove shape accuracy. In this study, a superhard diamond wheel V-tip was employed to perform a micro-grinding through a traverse grinding. After micro-grinding, these micro-grooves were characterized by the mean depth of 155.1 μm, the mean form error PV of 7.8 μm and the mean tip radius of 45.6 µm. Firstly, traditional plate tool, orthogonal micro-grooved tool and diagonal micro-grooved tool were employed to perform a dry turning of titanium alloy, respectively; then, tool wear, surface roughness, chip topography and shear angle were investigated. It is shown that the sharpened diamond wheel V-tip is valid to grinding micro-groove array on tool rake surface without any burrs. Furthermore, the micro-grooved tools may reduce the cutting sparks, tool wear, 3D chip size and chip saw-tooth size compared to traditional plate tool. The diagonal micro-grooved tool may decrease tool wear by 6.7% and surface roughness by 37.3% and increase shear angle by 24.3% against orthogonal micro-grooved tool, respectively. This is because the diagonal micro-grooving direction is identical to the cutting chip flowing on tool rake surface. It is confirmed that the diagonal micro-grooved tool is applicable to a stable dry cutting of titanium alloy.

Study of the processing properties of a nickel-based diamond film in the development of a miniature circular diamond-blade array

This study presents a hybrid fabrication technique for developing a diamond-blade array used to directly generate a microgroove array onto NAK80 steel. The microgroove array on the NAK80 steel can be used as a biochip mold. The diamond-blade array is made by depositing a nickel-based diamond film onto a disk tool (substrate) through electrochemical co-deposition. The nickel–diamond wheel blank is then cut using RWEDM (Rotary Wire Electrical Discharge Machining) to produce a multi grinding-edge array from the blank. The developed diamond-blade array is then employed in machining a microgroove array on NAK80 steel to produce a biochip mold. The resultant dimensional accuracy, geometric accuracy, and surface finish of the grinding-edge and finished microgroove array are measured and evaluated. The factors influencing formability, thermal machinability, and mechanical properties of the diamond film are discussed in detail. Experimental results indicate that a lower current density and moderate diamond abrasive concentration create a diamond film of high-integrity. Increasing the thickness of the deposited film suppresses thermal fracturing and raises the rigidity of grinding-edges helping to keep the diamond cutting-edge accurate. Nano-metric scale grinding of microgrooves on the NAK80 steel is helpful in maintaining sharpness and slowing the wear rate of the diamond-film grinding-edges.

Making human enamel and dentin surfaces superwetting for enhanced adhesion

Good wettability of enamel and dentin surfaces is an important factor in enhancing adhesion of restorative materials in dentistry. In this study, we developed a femtosecond laser surface texturing approach that makes both the enamel and dentine surfaces superwetting. In contrast to the traditional chemical etching that yields random surface structures, this approach produces engineered surface structures. The surface structure engineered and tested here is an array of parallel microgrooves that generates a strong capillary force. Due to the powerful capillary action, water is rapidly sucked into this engineered surface structure and spreads even on a vertical surface.

Development of a novel custom micro-tool for effective cutting of a precision microgroove array on a microscope slide

This study presents a novel, economical and efficient fabrication technique for precisely generating multiple microgrooves on a microscope slide to allow for microscopic examination of urine sediment cells. This study incorporates two important phases: a precision wheel-tool array is fabricated and then the developed tool is used in fast on-line grinding of multiple microgrooves. The wheel-tool blank is made of diamond grit of 0–2 µm grade via co-deposition. Subsequently, it is trued, sliced and sharpened by means of micro wire electro discharge dressing. The finished wheel-tool is utilized on-line to grind multiple microgrooves using ‘high-speed and fast-shallow grinding’. A ductile grinding regime is established to obtain a nano-metric surface finish for the multiple microgrooves generated on the microscope slide. The depth and width of the grooves in the array are both 10 µm and a surface finish of Ra equal to 0.010 µm is simultaneously achieved. This multiple microgrooving technique can supply high-quality fast grinding in the fabrication of bio-medical devices, such as those used for stationing and counting urine sediment cells.

Comparing Microgroove Array Forming with Micropyramid Array Forming in the Glass Molding Press

This paper presents a glass molding press (GMP) method to fabricate microgroove array and micropyramid array on the glass plate by replicating the shape of the mold to the glass surface. The differences between microgroove forming and micropyramid forming were investigated by experiments and finite element method (FEM) simulations. Microgroove arrays and micropyramid arrays were generated on the flat glass plate in the GMP process by using an electroless-plated Nickel Phosphorus (Ni-P) mold, on which the microstructures are fabricated by micro cutting. Furthermore, FEM simulations were used to trace the stress distribution and the strain distribution during the glass deformation, which illustrates the glass material flow in the microgrooves and the micropyramids on the mold during pressing. By comparing the processes between microgroove forming and micropyramid forming, the differences between them observed in the experiments were explained by the simulation results. Finally, some techniques to improve the forming accuracy were proposed.

Analysis of Stokes flow in microchannels with superhydrophobic surfaces containing a periodic array of micro-grooves

Superhydrophobic surfaces have been demonstrated to be capable of reducing fluid resistance in micro- and nanofluidic applications. The objective of this paper is to present analytical solutions for the Stokes flow through microchannels employing superhydrophobic surfaces with alternating micro-grooves and ribs. Results are presented for both cases where the micro-grooves are aligned parallel and perpendicular to the flow direction. The effects of patterning the grooves on one or both channel walls are also analyzed. The reduction in fluid resistance has been quantified in terms of a dimensionless effective slip length, which is found to increase monotonically with the shear-free fraction and the periodic extent of each groove–rib combination normalized by the channel half-height. Asymptotic relationships have been derived for the normalized effective slip length corresponding to large and small limiting values of the shear-free fraction and the normalized groove–rib period. A detailed comparison has been made between transverse and longitudinal grooves, patterned on one or both channel walls, to assess their effectiveness in terms of enhancing the effective slip length. These comparisons have been carried out for small and large limiting values, as well as finite values of the shear-free fraction and normalized groove–rib period. Results for the normalized effective slip length corresponding to transverse and longitudinal grooves are further applied to model the Stokes flow through microchannels employing superhydrophobic surfaces containing a periodic array of micro-grooves inclined at an angle to the direction of the applied pressure gradient. Results are presented for the normalized effective slip lengths parallel to the direction of the applied pressure gradient and the normalized cross flow rate perpendicular to the direction of the applied pressure gradient.

Improvement of surface roughness of aluminum products by the micro-grooves on tool surface in cold extrusion

The effects of the micro-groove arrays formed on the tool surface on the material flow, surface condition of a billet and surface quality of a product were investigated by carrying out the plane strain extrusion experiments. Paraffinic mineral oil and RBD palm olein were applied in the above experiments. The distributions of flow velocity and effective strain in a billet were analyzed by using the visio-plasticity method. The experimental and analytical results show that the extrusion load increases with the inflow of billet to the grooves. The results also show that the surface condition of the extruded product is smoother when the location of the micro-groove array is at the inner section in the deformation boundary and a paraffinic mineral oil was used. The surface quality of a product in an extrusion process could be improved, under a slight rise of the extrusion load by using a tool with micro-groove arrays were formed on the tool surface at an appropriate section.

Development of a Three Axis Controlled Fast Tool Servo for Ultra Precision Machining (2nd Report)

A new three-axis FTS system has been developed for ulrtaprecision machining. The 3-axis FTS unit can drive the cutting tool freely in the space by controlling the motion of the three piezoelectric actuators arranged along the three axes of the orthogonal coordinates. In order to carry out elliptical vibration cutting with the FTS unit developed, sinusoidal vibration commands are added in two directions. In this report, two methods are developed to generate the vibration command, one is to use the controller as the signal generator, and the other to add the external command signal. Series of micro groove cutting tests were carried out on Ni-P work with use of single crystal diamond cutting tool. It was proved that fine grooves without bur formation were generated by adding the circular vibration to the cutting tool. The V-shaped micro-groove array with flat ends was also machined successfully.

Microtopography and flow modulate the direction of endothelial cell migration

The migration of vascular endothelial cells under flow can be modulated by the addition of chemical or mechanical stimuli. The aim of this study was to investigate how topographic cues derived from a substrate containing three-dimensional microtopography interact with fluid shear stress in directing endothelial cell migration. Subconfluent bovine aortic endothelial cells were seeded on fibronectin-coated poly(dimethylsiloxane) substrates patterned with a combinatorial array of parallel and orthogonal microgrooves ranging from 2 to 5 microm in width at a constant depth of 1 microm. During a 4-h time-lapse observation in the absence of flow, the majority of the prealigned cells migrated parallel to the grooves with the distribution of their focal adhesions (FAs) depending on the groove width. No change in this migratory pattern was observed after the cells were exposed to moderate shear stress (13.5 dyn/cm(2)), irrespective of groove direction with respect to flow. After 4-h exposure to high shear stress (58 dyn/cm(2)) parallel to the grooves, the cells continued to migrate in the direction of both grooves and flow. By contrast, when microgrooves were oriented perpendicular to flow, most cells migrated orthogonal to the grooves and downstream with flow. Despite the change in the migration direction of the cells under high shear stress, most FAs and actin microfilaments maintained their original alignment parallel to the grooves, suggesting that topographic cues were more effective than those derived from shear stress in guiding the orientation of cytoskeletal and adhesion proteins during the initial exposure to flow.

A novel finned micro-groove array structure and forming process

The multidimensional finned surface can greatly improve the capability of separation, extraction, absorption and heat transfer, so it is wildly applied to modern environmental protection, petrochemical industry, medical industry, and micro-electronics cooling, etc. By ploughing-extrusion process, this paper obtained a novel micro-groove array structure composed of micro-grooves, primary fins and compound fins, which have macro-structure, meta-structure, and micro-structure. The depth of micro groove is about 200 μm, and the height of the primary fin is about 80 μm. The height of the compound fins is larger than 100 μm, and the space of two compound fins is about 400 μm. In this process, the metal undergoes plastic deformation and turns into primary fins. Owing to the friction stress between the extrusion surfaces and the metal surpass the break limit of the metal, some regions of the primary fin undergo ductile fracture and turn into denticular compound fins. The whole process can be divided into four steps, i.e. splitting, extruding, frictional tearing and fin forming. The four stages are continuous and happen at the same time. The novel finned micro-groove array structure can be manufactured in a single procedure.

Measurement of blood rheology using micromachined channel array.

Arrays of microgrooves (width 6, 7, and 8 μm; depth 4.5μm; length 10, 20, 30, 40, and 100μm; number 2600 or 4704 in parallel) photofabricated in the surface of a single-crystal silicon substrate were converted to arrays of leak-proof microchannels by tightly covering them with an optically flat glass plate. Using the microchannels as a model of physiological capillaries, total flow rate of blood was determined under a constant suction while flow behavior of blood cells in each channel was microscopically observed. Erythrocyte deformability, leukocyte adhesiveness, and platelet aggregability quantified by channel transit time or channel blocking and reopening rates showed changes caused by environmental factors such as diet and exposure to bacterial cells.