Fiber Holder Research Articles

Design, fabrication, and test of an on-chip micro flow cytometer with integrated out-of-plane microlenses

A micro flow cytometer with an integrated three-dimensional hydro-focusing unit and out-of-plane microlenses was successfully fabricated and tested. The entire system was fabricated with SU-8 ultra-violet lithography process. In the hydro-focusing unit, sheath flows pass through a trapezoid-shaped chamber with three 30° slopes to focus the sample flow in both horizontal and vertical directions. As an essential component in the on-chip optical detection system, integrated out-of-plane microlens was embedded in the sidewall of the fluid outlet channel in the detection area. A pre-aligned optical fiber holder was fabricated on chip to fix the output optical fiber in a position aligned to the microlens. Optical simulation and analysis were also conducted using commercial software Zemax. Numerical simulation results confirmed that the use of microlens substantially improved the detection efficiency by focusing the fluorescent light from the sample cells into the output optical fiber. Preliminary cell counting experiment was performed using the fabricated micro flow cytometer system and the experimental results proved the feasibility of the integrated micro flow cytometer design.

New fabrication techniques of SU-8 fiber holder with cantilever-type elastic microclips by inclined UV lithography in water using single Mylar mask

In contact UV lithography, a pair of cantilever beams fabricated by two inclined exposures at ±45° in SU-8 using a single mask will form a connected end on the top of SU-8 layer. These beams made of SU-8 with fixed-end have been used as optical fiber holders (Ling and Lian in Microsyst Technol 13(3–4):245–251, 2007). Recently, a two-mask, two-step process to fabricate free-end cantilever beams from SU-8 using inclined UV lithography has been developed (Ling et al. in Microsyst Technol 15(3):429–435, 2009), which has been successfully applied to fabricate SU-8 optical fiber holders with long free-end cantilever beams. In this process, two masks are needed in order to obtain free-end beams and the alignment between two exposures is always time consuming with limited accuracy. Two new techniques, inclined UV shadow mask lithography and inclined UV proximity lithography, have been illustrated here for fabricating free-end SU-8 cantilever beams, which eliminate the precise alignment step required in our previous work (Ling et al. in Microsyst Technol 15(3):429–435, 2009). In the inclined UV shadow mask lithography approach, the SU-8 cantilever beams without connected ends are formed by using one main mask and two shadow masks. Each shadow mask is used to selectively transfer one of the two separated patterns on main mask into SU-8 layer at +45° and −45°, respectively. In the inclined UV proximity lithography approach, a proper proximity gap between mask and SU-8 surface is obtained by using a 50 μm thick Mylar sheet, so that the exposing light paths that formed connected beam ends will fall inside the proximity layer instead of the SU-8. In this way, the desired open-end cantilever structures can be achieved. In this paper, the principles and the fabrication procedures of the proposed techniques are demonstrated and the preliminary results are discussed.

Design and fabrication of SU-8 micro optic fiber holder with cantilever-type elastic microclips

The optic alignment module containing out-of-plane 3D micro lenses, and micro optic fiber holders have been fabricated using tilted UV lithography technique in water with SU-8 photoresist (Ling and Lian in Proc SPIE 4979:402–409, 2007). Each holder is a circumscribed quadrilateral formed by a V-groove and pairs of fixed microclips, which will hold the fiber in position through the elastic deformation when the fiber is inserted. Since these microclips were fixed cantilever beams and its effective beam length, the distance between the fixed end of the beam and beam–fiber contact point, is very short (~62.5 μm), the stress on the beam is high even under a small (few microns) deformation. The inserted optical fiber was either too loose to lose its alignment accuracy, or too tight causing the clips to break because of dimensional tolerance. It becomes very difficult, if not impossible, to use them in practical applications. Therefore, the key issue of fabricating optical alignment module is to have a suitable stiffness of microclips with an appropriate deformation during the fiber insertion, which can provide enough force to hold the fiber for accurate alignment and avoid introducing neither significant viscous deformation nor the damage to the clips. In this paper, a novel technique to fabricate SU-8 cantilever beam as elastic clamping device in optical fiber holder is proposed. Simulation based on SU-8 material properties indicates that for a 250-μm-long, 50-μm-thick SU-8 beam the clamping force per unit beam width will range from 10 to 100 Newton/m as the deflection increased from 1.4 to 14 μm. This predicted performance is comparable to or even better than that of existing silicon nitride microclips in optical fiber holding application [Bostock et al. in J Micromech Microeng 8(4):343–360, 1998]. By using a two-mask process, we have fabricated free-end cantilever beams as fiber holding clips. In order to have longer beams over V-groove, the slots in the V-groove were introduced, which allow the beams extended deeper into the sloped V-groove walls. The micro alignment module with 250-μm-length cantilever beams as microclips for housing 125-μm-diameter optical fibers has been successfully fabricated using a 300-μm-thick SU-8 photoresist layer by a two-mask UV lithography processes. This approuch offers significant advantages over other techniques with respect to costs of material, simple in equipment, and easy in manufacture. These optical fiber holders with elastic microclips combined with pre-aligned out-of-plane 3D micro lenses make it possible that to build an integrated micro optic system with precise alignment accuracy on a wafer-scale.

Irrigation Eliminates Smoke Formation in Laser Laparoscopic Surgery

To evaluate the desmoke effects of irrigation on surgical smoke generated during laser laparoscopic surgery using ex vivo model. A hand-piece was devised as both an irrigation tube and a laser fiber holder. The laser system used was a diode pumped continuous wave Thulium YAG laser (Lisa laser products OHG, Katlenburg-Lindau, Germany) emitting at 2.01-mum through a quartz fiber with a core diameter of 365 mum. Using a transparent container as experimental model (approximately 3 L in volume), 6 irrigation rates (0, 20, 40, 60, 80, and 100 mL/min) were tested combining with 4 laser power settings (20, 30, 40, and 50 W). To evaluate the desmoke efficiency of irrigation, lasing time with effective visibility under different combination of irrigation rates and laser powers were documented, and corresponding smoke generation rate were calculated (=3 L/lasing time). Analysis of variance was used to compare difference and significance was indicated at P<0.05. Calculated smoke generation rate was increased with laser power whereas decreased with irrigation rate. At 4 tested laser powers, calculated smoke generation rates were high (mean: 91.4 to 306.6 mL/s) when no water presented, but were significantly decreased (mean: 12.6 to 55.0 mL/s, P<0.001) with the lowest water flow rate (20 mL/min) and further decreased with higher rates. The proper range of irrigation rate for future clinical practice would be around 40 mL/min. Irrigation eliminates smoke formation accompanying laser tissue irradiation. It shows promise for future application in laser laparoscopic surgery.

Enrichment sampling methods for wine discrimination with gas sensors

A comparison between two sampling methods based on sample concentration (purge and trap (PT) and solid-phase micro-extraction (SPME)) applied to gas sensors (electronic nose) for wine discrimination is performed. Two different traps have been used in the Tekmar 3100 purge and trap concentrator: trap containing Tenax and Tenax/silica gel/charcoal. Four different types of fiber coating have been used for SPME method: 100 μm polydimethylsiloxane (PDMS), 65 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB), 85 μm polyacrilate and 75 μm carboxen/polydimetilsiloxane (CAR/PDMS). The cell containing a tin dioxide multisensor was mounted inside the gas chromatograph (GC) oven, connected to the injector by replacing the chromatographic column. In this way, the GC injection port has been used to connect the purge and trap and fiber holder to sensors cell. Samples of five different wines elaborated with the major varieties of DO Vinos de Madrid were used for testing the discrimination capability of the systems. Multivariate analyses as principal component analysis (PCA) and artificial neural netwoks (ANN) have been applied to the data to discriminate among the different wine samples. Results show that purge and trap technique provide better response. Tenax trap and 85 μm polyacrilate fiber obtained the highest success rate in classification.

Thermodynamic formalism for random countable Markov shifts

We introduce a relative Gurevich pressure for random countable topologically mixing Markov shifts. It is shown that the relative variational principle holds for this notion of pressure. We also prove a relative Ruelle-Perron-Frobenius theorem which enables us to construct a wealth of invariant Gibbs measures for locally fiber Holder continuous functions. This is accomplished via a new construction of an equivariant family of fiber measures using Crauel's relative Prohorov theorem. Some properties of the Gibbs measures are discussed as well.

Fiber Assembly of MEMS Optical Switches With U-Groove Channels

A key process in assembly of microelectromechanical systems optical switches is of inserting fibers into U-grooves in silicon substrate. Due to positioning errors and dimensional tolerances in components, heavy collision occurs between fibers and the edges of U-grooves during insertion, throwing out fibers from the fiber holder or worse, damaging the components. Typical solutions to the problem involve determining errors using machine vision or force sensors, and then positioning fibers accurately by virtue of high precision multi-axis systems (with submicron repeatability). However, these approaches are costly and difficult to implement. In this paper, we present a low-cost passive assembly method to solve the problem. It utilizes a special flexure-based fixture to regulate high contact forces and accommodate assembly errors. Specifically, we model the problems happening in the process of fiber insertion and characterize the conditions of successful insertion. We then suggest how to design flexural fixtures so that the required insertion conditions can be met. Experimental results show that using such a fixture the fiber assembly can be successfully implemented even if the assembly system's accuracy is lower than 12 in and axes, and 0.07 in theta axis. These requirements are within the reach of most low-cost precision systems.

Microengineered Two-Dimensional Arrays of Monomode Optical Fibers

In this paper, a method to manufacture 2-D bundles of single-mode optical fibers of highly accurate pitch is presented. Electrostatic actuation of the metal-clad optical fibers is performed to align the fibers with submicrometer translational alignment accuracy. The manufacturing and alignment performance characteristics of the fiber holder are fully described. The sensitivity of the active-alignment procedure for a maximum displacement up to 90 mum is between 0.125 and 1.1 mum, depending on the clamping distance. An alignment accuracy of around 0.2 mum can be achieved with this alignment method. The combination of the electrostatic actuation with the optical monitoring of the fiber pitch in a closed-loop feedback system provides a highly accurate and sensitive alignment system.

Integration of a UV curable polymer lens and MUMPs structures on a SOI optical bench

This work presents the design concept of integrating a polymer lens, poly-Si MUMPs and single-crystal-silicon HARM structures on a SOI wafer to form a silicon optical bench. This approach enables the monolithic integration of various optical components on the wafer so as to improve the design flexibility of the silicon optical bench. Fabrication processes, including surface and bulk micromachining on the SOI wafer, have been established to realize bi-convex spherical polymer lenses with in-plane as well as out-of-plane optical axes. In addition, a micro device consisting of an in-plane polymer lens, a thick fiber holder and a mechanical shutter driven by an electrothermal actuator is also demonstrated using the present approach. In summary, this study significantly improves the design flexibility as well as the functions of SiOBs.

Time-weighted average water sampling with a diffusion-based solid-phase microextraction device

A new diffusion-based solid-phase microextraction (SPME) time-weighted average (TWA) field water sampling device was developed and investigated by field trial. The sampler is constructed with copper tube and caps and a commercial SPME fiber assembly. The device possesses all advantages of SPME; it is solvent-free, reusable, combines sampling, isolation and enrichment into one step, and the fiber can be directly injected into a gas chromatograph for analysis with a commercial SPME fiber holder, without further treatment. Field trials in Laurel Creek (Waterloo, Ont., Canada) and Hamilton Harbour (Hamilton, Ont., Canada) illustrated that the device is durable, easy to deploy, and the mass uptake of the device is independent of the face velocity. The device provides good precision [relative standard deviations (RSDs) are less than 20%] and the data obtained with this device are quite comparable to those obtained with the spot sampling method, which demonstrates that the newly developed SPME water sampling device is suitable for long-term monitoring of organic pollutants in water.

Improvement of HS-SPME for analysis of volatile organic compounds (VOC) in water samples by simultaneous direct fiber cooling and freezing of analyte solution

The sensitivity and precision of headspace solid-phase micro extraction (HS-SPME) at an analyte solution temperature (T (as)) of +35 degrees C and a fiber temperature (T (fiber)) of +5 degrees C were compared with those for HS-SPME at T (as) and T (fiber) of -20 degrees C for analysis of the volatile organic compounds benzene, 1,1,1-trichloroethane, trichloroethylene, toluene, o-xylene, ethylbenzene, m/p-xylene, and tetrachloroethylene in water samples. The effect of simultaneous fiber cooling and analyte solution freezing during extraction was studied. The compounds are of different hydrophobicity, with octanol/water partition coefficients (Kow) ranging from 126 and 2511. During a first set of experiments the polydimethylsiloxane (PDMS) SPME fiber was cooled to +5 degrees C with simultaneous heating of the aqueous analyte solution to +35 degrees C. During a second set of experiments, both SPME fiber holder and samples were placed in a deep freezer maintained at -20 degrees C for a total extraction time of 30 min. After approximately 2 min the analyte solution in the vial began to freeze from the side inwards and from the bottom upwards. After approximately 30 min the solution was completely frozen. Analysis of VOC was performed by coupling HS-SPME to gas chromatography-mass spectrometry (GC-MS). In general, i.e. except for tetrachloroethylene, the sensitivity of HS-SPME increased with increasing compound hydrophobicity at both analyte solution and fiber temperatures. At T (as) of +35 degrees C and T (fiber) of +5 degrees C detection limits of HS-SPME were 0.5 microg L(-1) for benzene, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene, 0.125 microg L(-1) for toluene, and 0.025 microg L(-1) for ethylbenzene, m/p-xylene, and o-xylene. In the experiments with T (as) and T (fiber) of -20 degrees C, detection limits were reduced for compounds of low hydrophobicity (Kow<501), for example benzene, toluene, 1,1,1-trichloroethane, and trichloroethylene. In the concentration range 0.5-62.5 microg L(-1), the sensitivity of HS-SPME was enhanced by a factor of approximately two for all compounds by performing the extraction at -20 degrees C. A possible explanation is that freezing of the water sample results in higher concentration of the target compounds in the residual liquid phase and gas phase (freezing-out), combined with enhanced adsorption of the compounds by the cooled fiber. The precision of HS-SPME, expressed as the relative standard deviation and the linearity of the regression lines, is increased for more hydrophobic compounds (Kow>501) by simultaneous direct fiber cooling and freezing of analyte solution. Background contamination during analysis is reduced significantly by avoiding the use of organic solvents.

Carbon fiber technique for the investigation of single-cell mechanics in intact cardiac myocytes

This protocol describes a method for attaching single isolated cardiac myocytes to carbon fibers for mechanical manipulation and measurement. This method relies on cell-adhesive carbon fibers that attach easily to the cell membrane without causing damage, and is thus applicable to intact myocytes. To connect the carbon fiber to micromanipulators, a fiber holder with glass capillaries must first be fabricated. After connection of the fibers to the micromanipulators, firm attachment is easily established by gently pressing the fiber tip onto the cell membrane. Unlike other methods, this technique does not require vast technical expertise, and therefore greatly facilitates experiments. This method enables detection of the effect of drugs, genetic defects or the expression of exogenous proteins on both active and passive properties of cardiac myocytes. In combination with other experimental procedures, this technique can also be applied to the study of mechano-transduction. This protocol can be completed in 3.5 h.

A novel micro/nano 1 × 4 mechanical optical switch

This paper presents the design, fabrication and testing of a novel 1 × 4 mechanical optical switch, whose components are fabricated by precision machining and MEMS technologies. The switch uses two relays as the two actuators whose switching direction is perpendicular to each other by an orthogonal arrangement. We adopt a direct fiber-to-fiber principle that aligns the input fiber directly to four output fibers. This configuration eliminates the use of traditional parts such as collimators, turning mirrors or prisms. In addition, due to the use of a fiber holder, the fiber position errors could be reduced to less than 0.27 µm using the two-stage geometry error reduction principle. We have successfully developed a simple and low-cost switch, which performs like most of the 1 × 4 mechanical optical switches that dominate the optics communications market. The advantages of our switch are a small size (20 × 20 × 25 mm3), low cost, high reliability, and the latching function does not need external force for maintaining the state. The experimental results showed that the insertion losses of the four channels are ch1: 0.68 dB, ch2: 1.49 dB, ch3: 0.71 dB and ch4: 0.97 dB. The switching time is 5 ms, the crosstalk ⩽80 dB. The reliability tests of the insertion loss after 10 000 cycles in four channels yield ch1: 1.67 dB, ch2: 1.63 dB, ch3: 0.75 dB and ch4: 0.98 dB. The size and the cost of our 1 × 4 mechanical optical switch are only about 1/5–1/10 and 1/10 of the series-connect-type and prism-type switches, respectively.

SU-8 3D microoptic components fabricated by inclined UV lithography in water

Out-of-plane microlenses and microoptical fiber holder are two of the most important components for building an integrated microoptic system with a precise alignment accuracy. In this paper, a simple and convenient method to fabricate these components from SU-8 by using inclined UV lithography in water is proposed. It consists of two perpendicular exposures in SU-8 at ±45°. DI water possesses a low absorption coefficient and a moderate and stable value of refractive index in near UV. Using water, the exposure angle in SU-8 can be increased to 50° from 35° in air necessary to pattern the desired 45° slope of the sidewalls. The principle of the proposed technique and the detailed fabrication process of the microoptic components will be presented. The integratability of the fabricated components was demonstrated by the fabrication of the microoptical fiber holder with a pre-aligned out-of-plane microlens.

Construction and performance of 128-channel segmented pulsed μSR and μe detection system at Dai Omega

In order to perform μSR and μe measurements with an instantaneously intense pulsed 4-MeV muon beam currently available at Dai Omega, which is a large solid-angle-axial focusing superconducting surface muon channel at KEK-MSL, the detector segmentation in the conventional digital technique was improved to accept the predicted event rate of 2.0×10 4 muons/spill. A new detection system was designed to collect intense μe decay positrons with 128 two-fold coincidence detector elements. A major feature of the new detection system was an employment of multi-anode phototubes (MAPMT) to make the detection system be compact. We mitigated the problems related cross talks among channels by employing a special fiber holder. The performance of the detection system was confirmed by μSR and μe test experiments.

A miniature low cost and high reliability 1 × 2 mechanical optical switch

This paper presents the design, fabrication and tests of a miniature 1 × 2 mechanical type optical switch, whose components are fabricated by precision machining and MEMS technologies. The packaging and alignment are integral processes utilizing the CCD image processing technique and PZT-stages controlled technique in association with the optimization software enabling the fiber-to-fiber alignment to low optical loss requirement. Optical fibers in use have the following specifications: single-mode fiber (SMF) outer diameter 125 µm, core diameter 9 µm, zero degree of the fiber tip angle and non-anti-reflection coating. The initial gap of the input and output fibers is 10 µm. First, we produced a fiber holder and a V-groove by MEMS technology and used a relay as the input fiber switching actuator. Through proper mechanism design, the fiber positioning error can be reduced to below 0.1 µm. After the optimized alignment process, the results presented that the insertion loss could be controlled to ch1: 0.8 dB, ch2: 1.4 dB at a switching time of 5 ms. The reliability tests demonstrated that the variation of the insertion losses are ch1: 0.04 dB, ch2: 0.02 dB after 10 000 cycle times, and ch1: 0.024 dB, ch2: 0.006 dB throughout 100 switch times after 1 000 000 cycle times. The developed 1 × 2 optical switch largely reduces the physical size to 1/2–1/3 in comparison with traditional mechanical optical switches, and the cost is only about 1/10–1/20 of the MEMS type optical switches. The advantages of this innovative optical switch are: small size (only about 20 × 16 × 7.5 mm3), low cost (only about US$10), high reliability, cross-talk ≦ −80 dB and automatic alignment.

Implementation of an All-Fiber Variable Optical Delay Line with a Pair of Linearly Chirped Fiber Bragg Gratings

We implemented all-fiber delay line using linearly chirped fiber Bragg gratings (CFBG), which can be applicable for reflectometry or optical coherence tomography (OCT). Compared with the previously reported delay lines, the proposed fiber-based optical delay line has in principle novel advantages such as automatic dispersion cancellations without additional treatment and a gain in optical delay that is dependent on parameters of used CFBGs. Dispersion compensation in optical delay line (ODL), which is the indispensable problem in bulk optics based ODL, is demonstrated in fiber by using two identical but reversely ordered CFBGs. Amplified variable optical delay of around 2.5 mm can be obtained by applying small physical stretching of one of CFBGs in the proposed scheme. The operational principles of the all-fiber variable optical delay line, which are based on the distributed reflection characteristic of a CFBG employed, are described. Especially properties such as in-line automatic dispersion cancellation and amplified optical delay under strain are dealt. To demonstrate the properties of the proposed scheme, which is theoretical consequences under assumptions, an all-fiber optical delay line have been implemented using fiber optic components such as fiber couplers and fiber circulators. With the implanted ODL, the group delay and amplified optical delay length was measured with/without strain. The wavelength independent group delay measured within reflection bandwidth of the CFBG has proved the property of automatic dispersion cancellations in the proposed fiber delay line. Optical delay length of 2.5 mm was obtained when we apply small physical stretching to the CFBG by 100μm and this is expressed by the amplification factor of 25. Amplification factor 25, which is less than theoretical value of 34 due to slipping of fiber in the fiber holder, shows that the proposed scheme can provide large optical delay with applying small physical stretching to the CPBG. We measure slide glass thickness to check the performance of the fiber delay line and the good agreement in measured and physical thickness of slide glass (∼1 mm thick) validates the potential of proposed delay line in the applications of optical reflectometry and OCT. We also discuss the problem and the solution to improve the performance.

Development of Fe-Mn-Si-Cr Shape Memory Alloy Fiber Reinforced Plaster-Based Smart Composites

In previous studies, it has been found that the shape memory effect of the embedded straight and wavy shape memory alloy (SMA) fibers enhance the strength and energy absorption prior to fracture of the composite, where the embedded SMA fibers shrink due to their shape memory effect. In the case of wavy fiber reinforced composites, the SMA fibers were subjected to pre-tensile strain using fiber holder with rotatable rollers to maintain the constant periodicity and amplitude of wavy fibers. In this study, on the other hand, the wavy SMA fibers were subjected to pre-tensile strain without using fiber holder, and therefore, periodicity and amplitude of wavy fibers were varied during the deformation. Then the wavy SMA fiber reinforced smart composite is fabricated. For the mechanical property characterization, three-point bending test is performed for the specimens.

Thomson scattering upgrades on Alcator C-Mod

The Thomson scattering (TS) diagnostics set has been upgraded to deliver measurements of electron temperature (Te) and density (ne) with improved temporal and spatial resolution. Two 30 Hz, 1.3 J Nd-doped yttrium–aluminum–garnet (Nd:YAG) lasers share a vertical beam path through the tokamak plasma and are fired in an alternating fashion, allowing the collection of scattered light with a 60 Hz repetition rate. Eight compact polychromators have been added to the system, better than doubling the spatial resolution of core plasma TS measurements and allowing better diagnosis of core ne and Te gradients. Each fiber holder can be repositioned easily, making it possible to concentrate core measurements in the regions of particular interest with a spatial resolution of ∼1 cm. The newly designed mount can be positioned with submillimeter precision, and its alignment with respect to the Nd:YAG beam can be adjusted between discharges using remote controlled stepper motors. Cross calibration of TS ne measurements with electron cyclotron emission (ECE) diagnostics is performed using dynamic ramps of both plasma density and magnetic field to force ECE signal cutoffs at known values of ne. This technique supplements an absolute calibration based on Raman scattering in hydrogen and deuterium gas.

On the out-of-plane deformation of V-shaped micromachined beams

V-shaped beams are widely applied for the suspension of thesensors, fiber holders, and the suspension arms of atomic force microscopes.The performance of the V-shaped beam is highly dependent upon its initialout-of-plane deflection. This paper reports on the exploration of theout-of-plane deformation of V-shaped micromachined beams. A finite elementmodel has been established to predict the deformation of a V-shapedmicromachined beam. The fabrication and characterization of various shapes ofSiO2 V-shaped micromachined beams has been performed to observe theout-of-plane deformation caused by residual stress. With the differencebetween the analytical and experimental results, an etching process dependentmechanism has been discussed. Thus the design criteria to fabricate a flatV-shaped beam is accomplished.