We report an electromagnetic inductance/coil-based non-destructive method to target distal screw-holes in an intramedullary interlocking-nail surgical operation for fixing a long-bone fracture. The method is a radiation-free approach addressing the over-exposure issue of radioactivity caused by the typical X-ray-imaging approach. According to the method, we fabricate a targeting-system consisting of an internal inductance, external coil, guiding-mechanism, and driving/measurement electronics. When a voltage is applied to the internal inductance embedded in one of the distal screw-holes of a nail inserted in a bone, a directional magnetic flux is generated by the internal inductance due to the electromagnetic induction. Subsequently, the directional magnetic flux penetrates the nail and bone. When the external coil outside the bone scans along the axial and angular directions of the nail/bone, different amount of the generated magnetic flux is detected by the coil and consequently corresponding voltage response is induced in the coil due to the electromagnetic induction. In contrast to the magnetic flux generated and detected by the inductance and coil, respectively, we also investigate the reverse physics-behavior of the flux transmission (i.e., flux generated and detected by the coil and inductance) in order to improve the approach. Finally, by correlating the induced-voltage responses with the scanned axial-locations along the nail/bone, correlation curves are plotted. Through analyzing the curves, a criterion for predicting the location of the screw-holes of the nail is established. When compared the predicted location with the actual location of the screw-hole, the maximum targeting error is 2 mm for locating a screw-hole with a diameter of 5 mm. The result shows the targeting-method is accurate, fast, and easy for the surgeons and significantly simplifies the existed interlocking-nail surgical procedures.
This paper proposes an integrated model of a scratch drive actuator (SDA) based on a fourth-order governing equation of the Euler-Bernoulli theory. By solving this equation with proper boundary conditions, typical SDA output characteristics, such as noncontact length, priming voltage, deflection curve, output force, and bending stress, can be determined. The results of the output force in a static model are then used as the input of single degree-of-freedom dynamic SDA model to investigate the friction effect. Electroplated nickel SDA arrays, 80 μm in main beam length and 65 μm in width with a suspended spring, are fabricated and tested. The average travel distances after 1500 input pulses of 80-120 V are measured and found to be from 4.7 to 12.9 μm. The average measured output forces are from 10.2 to 28.3 μN. The simulation from the dynamic model is closer to the measured total travel distance and the output force than the static model, in general. The difference between simulations and experimental data due to energy dissipation can be reduced by including the friction effect in the dynamic model. Deviations between simulations and measured results are less than 10% in full range showing the superior capability of the proposed SDA model.
We present an improved method for manufacturing microfluidic structures on a polymer-based substrate, and the design of experiment (DOE) is used to extract the optimum injection parameters. The long cycle time of the injection molding causes high costs in manufacturing, and this prevents conventional techniques from being widely used for mass production. Therefore, this study adopts a new optical disk process to reduce the cycle time. The cycle time of the new method can be reduced by more than ten-fold compared with that of traditional ones. Also, this new method can prevent damage on the mirror plate of the mold. The mold system is composed of a mold insert (stamper) holder and a vacuum system to join the mold insert with the mold. In this way, the time needed to change the stamper is drastically decreased. Our proposed method has the ability to reduce the time required to insert the mold from several hours to a few minutes, to prevent damage on the mirror plate of the mold, and to decrease the cycle time of molding from several minutes to 4 sec. The DOE is applied to study the effects of molding parameters on replication rate of depth, width deviation, birefringence, tilt and surface roughness of the microfluidic substrates. The experimental results show that the proposed method is suitable for mass production.
Optical MEMS devices rely on the micro assembly to achieve re-positioning, such as lifted up micro mirrors and lens
and micro resistance welding benefits assembly of optical components. However, the characteristics of micro resistance
welding are still unknown. The purpose of this study is to characterize micro resistance welding with electro-thermal
actuator for micro assembly. In order to characterize influence of operation parameters on micro resistance welding,
important parameters including contact pressure, contact resistance and electrical energy are calibrated. Further,
welding strength provide robust join are also measured. The idea of resistance welding is based on generated heat by
Ohm's law to melt material. From measured results, contact resistance decreases with increasing contact pressure due to
increasing contact area. The stronger welding strength can be achieved at a smaller initial contact resistance which
means that a larger clamping force could enhance the welding strength. The maximum welding strength is 74.4 μN at
2.7 ΩFurther, welding energy affects yield significantly. At high welding energy, between 1 to 10 J, the yield can
reach 100%. The energy below 0.05 J would not generate adequate heat to weld structure.
Here, interconnection technique to link digital microfluidic chips is proposed. Three kinds of digital microfluidic
modules with connecting interface, including flexible module and two types of connector modules, are designed and
fabricated. Since these modules are fabricated on a compliant polymer-based substrate (ITO PET), chip-to-chip droplet
transportation even at different planes can be achieved by the proposed technique. A low-temperature fabrication process
is developed for the polymer substrates, where the SU-8 acts as the insulator. Droplet transportation through
electrowetting on curved surface is confirmed by testing on the bended flexible modules with different curvatures from 0
to 0.06 mm-1 at around 70 VAC. Then the droplet transportations between flexible and connector modules are investigated.
It is found that the gap size between two modules and the sidewall profiles at interface affect the droplet transportation
directly. For the gap size around 50μm with a smooth perpendicular sidewall profile, 80 VAC is shown to actuate droplet
of 1.5 μl, 2.5 μl, or 3.5 μl to cross over the interface successfully.
An accelerometer with concise structure having a resonant microbeam to measure 2-D acceleration is proposed. This structure is configured with a central proof mass suspended by four symmetrical and orthogonal high-aspect-ratio (HAR) microbeams. This dual-axis design is able to decouple a two-axis signal from a 2-D acceleration. An analytical model relating the linear relationship between the acceleration and the associated resonant frequency shift of microbeam is derived, and a finite element analysis (FEA) is also performed to confirm this model. The FEA result also shows that there is little cross talk between x and y directions of measurement, meaning that this structure is able to decouple a planar 2-D acceleration into two independent acceleration components, and therefore the 1-D analytical model can be used to evaluate the 2-D acceleration on the x-y plane. In addition, the model is verified by testing results of one conventional dual-axis natural frequency shifted microaccelerometer (DFSM). The simulation result also shows that the sensitivity of the proposed HAR accelerometer is triple that of a conventional DFSM.
The actual performance of a miniature mechanism significantly depends on the geometric quality of the machined part and specific features therein. To fabricate functional parts and features with accuracy and precision within +/- 1 μm or less, the laser micromachining system requires the capabilities of following the desired toolpath trajectories with minimum dynamic errors, high positional repeatability, and synchronization of laser firing events at precise time-and-location to ablate the material. The major objectives of this study are to fabricate miniature functional mechanisms using precision laser micromachining method, explore the machining challenges and evaluate the geometrical quality of the machined parts in terms of accuracy, precision and surface quality. Two functional mechanisms based on electro-thermal actuation have been studied. Several machining challenges related to the corner accuracy, the asynchronization of motions and, the laser-on/off events in space and time with respect to the part geometry have been addressed. The source of inaccuracies primarily stems from the geometric complexity of the mechanism that consists of several features, such as, arcs, radii, lines, curvatures, segments and pockets, along with their dimensional aspect ratio. Such a complex design requires a large number of inconsecutive trajectories to avoid thermal deformations. Copper and nickel foils with a thickness of 25 and 12.5 µm respectively were used in the fabrication of the prototypes. The machining challenges were successfully tackled and the geometrical performance of the fabricated prototypes was evaluated. Local feature accuracies within 0.1 - 0.2 µm have been recorded.
The materials owning the rough surface have been adopted in many applications, such as MEMS devices, solar cell, DRAM, and so on. However, the modified targets on the previous methods were almost limited to silicon-type materials, and some had the limitations in the material properties. Recently, a process combining spin-on photoresist and one-step RIE was proposed to modify various materials, which can be etched by RIE. Here, a modification process, which combines spin-on photoresist, two-step RIE, and wet etching, is proposed to extend the feasible materials to be modified, because more materials can be etched by chemical solutions. Also, it is a low temperature process, and no extra mask is needed. From the experimental results, the modified surface can be used to alleviate stiction of microstructures, and a detachment length is found to be about 2.2 times longer than the cantilevers without the modified surface. Moreover, the related parameters for the anti-stiction are also developed, and the effects are compared with the previously developed one-step RIE method.
As the recording density of longitudinal magnetic storage increases at a 100% annual growth rate, it will soon approach the superparamagnetic limit where the thermal energy at room temperature starts to induce thermal instability to the grains in the small recorded marks. Thermal magnetic recording schemes, such as those used in magneto-optical recording, help alleviate the problems with the superparamagnetic limit. Recently, a hybrid recording system was proposed where data were recorded thermal magnetically on a magneto-optical disk and read back with a GMR head. In this paper, we propose an integrated planar read that combines an optical fiber lens, a solid immersion lens, a sub wavelength aperture, a micro coil, an air bearing surface, and a GMR head for such a hybrid recording system. Preliminary fabrication and calculation are discussed.
Here the attenuation effect of a variable optical attenuator (VOA) with a tunable non-smooth mirror is investigated experimentally and analytically. The working principle of this VOA is based on the non-uniform deformation shape of a mirror membrane by thermally driven bimorph actuators. Before deformation, the surface roughness of Rymax and insertion loss of the mirror membrane are calibrated as 15 nm and 0.53 dB, respectively. The attenuation tests on smooth and non-smooth concave mirrors are also conducted. In simulation, the attenuation effects by various smooth spherical shapes are modeled by ray tracing method and Gaussian beam theory, and the simulation results are compared with experimental data. It is found that the attenuation behaviors between simulation and calibration results on smooth, spherical concave mirrors have good agreement. Also, by comparing the experimental results from smooth and non-smooth concave mirrors, the attenuation is found to be enhanced by the non-smooth mirror surface evidently. The maximum dynamic range of attenuation is found to be more than 40 dB at input voltage of 46 V.
Although lots of works have been devoted to develop the microactuators or microstructures, few researches have been done on three-dimensional microactuators. Here the feasibility investigation on a three-dimensional electro-thermally driven long-stretch micro drive (LSMD) is proposed by integrating the LSMD and mechanical hinge mechanism. The LSMD (about 2000 μm×500μm) consists of two cascaded compliant structures in parallel. Each cascaded structure is formed by connecting several basic actuation units in series. The mechanical hinge is used to allow the LSMD to be lifted as a three-dimensional structure. One of the important issues in fabricating the three-dimensional microactuator is the conducting circuit to actuate the microactuator. Here the Ni electroplating process is used to fabricate the mechanical hinge structure and the LSMD, then the mechanical hinge itself can act as the conductive circuit easily.
From the LSMD simulation results, several design parameters are found to have significant influence on the output displacements. Larger out-stretching displacements are feasible by proper choice of design parameters. Preliminary fabrication results of nickel-made LSMD exhibit output displacement of 190 μm at input voltage of 3 volts. Fabrication results of nickel-made three-dimensional LSMD are also presented
SU-8 photoresist has been popularly used as a mold for electroplating and facilitated low-cost MEMS production in many previous researches. However, the reachable thickness of electroplated structures standing on the substrate were limited to 50 μm below due to the internal stress and deformation of the SU-8 resist in final stripping process. In order to fabricate thicker structures, an embedded root method has been proposed to consolidate the adhesion of the metal structures to the substrate during the SU-8 removal process. In this paper, detailed investigation on this method is conducted to characterize the relationship among the root depth, the line-width and the allowable thickness of the electroplated structures. Some test patterns with embedded roots are designed and tested to generalize the possible extent of various structural scales associated with different niches in depth, which are completely defined through SiO2 masking and KOH etching processes. Based on establishment of the relationship between the root depth and the geometric sizes, a 3-D integrated coil with 200 μm in thickness, 80 μm in width and 4 μm in root depth is successfully released by the SU-8 mold with 400 μm in height, which can not be achieved by the standard SU-8 molding process. The UV-LIGA process presented herein may be applied to the fabrication of other microstructures and microactuators.
In ICP-RIE process, there have been many investigations on etching rate. However, only few published reports mentioned the sidewall roughness, which is a critical issue for optical devices. Here, experimental investigations about fabrication parameters in the STS Advanced Silicon Etch (ASE) process for sidewall roughness are performed. In our experiments, the photoresist of AZ1500 is used, and several parameters in the ASE process like over time, ramping time, Ar flow rate, platen power, and etching cycle time have been systematically studied. It is found that sidewall mean roughness can be down to 9.11 nm at etching rate of 2.5 micrometers /min. Comparing with other published works at similar sidewall roughness (around 10 nm), our experimental data have the highest etching rate. For the same STS ICP-RIE systems, our data have smallest sidewall roughness, comparing to previous literatures.
While the micro bimorph structures are fabricated with enough initial curvatures or so-called geometrical imperfections, structural instability may occur to result in snap-through behaviors and exhibit large deflection strokes. The bimorph structures with various initial deflections ratios and various heating area ratios are simulated and fabricated to predict the stable and unstable regions of the curved bimorph structures with clamped boundary condition. Four major types of load-deflection curves are described and discussed. Testing results and some observations are reported.
With the demanding of handling micro objects, the development of micro-clamper has emerged. Here an electro-thermally driven micro-clamper with adjustable vertical position is proposed. This micro-clamper is consisted of an adjusting unit and a clamping unit. The adjusting unit formed by two bimorph beams in the longitudinal direction can move the clamping unit vertically. The clamping unit formed by a pair of bimorph beams at the end of the adjusting unit is in the transversal direction. Due to the residual stress difference in the bimorph beams, at initial state, the adjusting unit in the longitudinal direction will bend upward, and the other two bimorph beams will also curl up to become a clamper. When the adjusting unit is heated, the whole device will move downwards. When the clamper unit is heated, two sides of the clamping unit will open up to a waiting state. It is hoped that the capability of adjusting the clamper in vertical position will provide larger operating range for the micro-clamper. The micro-clamper proposed here is batch-fabricated by surface micromachining. The testing results show that the adjusting unit can produce 8micrometers downward displacement at input voltage of 2V and the clamping unit can be fully flattened around 5 V.
In the current paper, the fabrication process of a novel proposed hemispherical polysilicon shell standing on a hemispherical silicon cavity is demonstrated. This micro-fabrication process combines both bulk and surface micromachining, which include the isotropic wet etching, a novel mask design, the thick photo resist coating and exposure, and high-aspect-ratio curved sacrificial technique. In isotropic wet etching of a hemispherical cavity, the optimal concentration of etchant is experimentally determined along with adequate ultrasonic vibration during wet etching to produce the circle-like of hemispherical cavity. The conventional alignment mark, which will be destroyed during the rather long isotropic wet etching process, is replaced by a novel mask design with the second alignment mark. Also, for a deep hemispherical cavity larger than 100úgm, the traditional photo resist can not be coated on the corner surface well. The thick photo resist, AZ4620, is found to be able to overcome this problem and be successfully exposed all through its bottom surface. Furthermore, the deposited sacrificial layer materials (PSG) on this cavity will usually result in thinner layer near the corner. In addition, the curved gap of PSG layer has the feature with high-aspect-ratio. These make the PSG etching difficult. Therefore, two steps etching process with two different hydrofluoric concentrations are used to release the PSG with 2micrometers thickness and 150micrometers arc length.
A micro membrane vibrator consisting of bimorph cantilever beams and a membrane is designed, fabricated, and tested here. Due to the discrepancy of thermal expansion coefficients between different layers, the membrane moves with temperature change. The four-layer structure including SiO2-polysilicon- insulated SiO2-aluminum is fabricated with four masks. The numerical finite element program ANSYS 51 is used to investigate the behavior of different designs to have larger displacement and force. According to the testing results, we observe that our designs can induce the maximum Z-axis displacement up to 117 micrometer when input power is 6.98 W. The working frequency is about 40 Hz when the amplitude is kept between 2 and 5 micrometer approximately.
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