Dual Micro Research Articles

Low cost dual axis micro force sensor for robotic manipulations

A multi-dimensional force measurement device often plays an important role in micro robotic manipulations. Due to the high level required accuracy and physical dimensions of the sensors, they are normally fabricated through a series of MEMS process which makes the sensors not only prohibitive but also vulnerable to an excessive loading operation environment. In this article, an inexpensive force measurement using strain gauges is developed and tested. Combining a mechanical structure optimization and signal processing technique, the present work provides a fairly precise force measurement in sub-micron Newton scale. In addition, the developed concept is expanded to a dual axis force measurement which extends its application to the micro particle robotic manipulations.

Controlling Zeolitic Imidazolate Framework Nano- and Microcrystal Formation: Insight into Crystal Growth by Time-Resolved In Situ Static Light Scattering

We report on a simple and straightforward method that enables the rapid room-temperature production of nanocrystals (finely tuned in size between ∼10 and 65 nm) and microcrystals (∼1 μm) of the prototypical microporous zeolitic imidazolate framework (ZIF) material ZIF-8. Control of crystal size is achieved in a novel approach by employing an excess of the bridging bidentate ligand and various simple auxiliary monodentate ligands with different chemical functionalities (carboxylate, N-heterocycle, alkylamine). The function of the monodentate ligands can be understood as a modulation of complex formation and deprotonation equilibria during crystal nucleation and growth. Using time-resolved static light scattering, the functioning of modulating ligands is monitored for the first time by in situ experiments, which offered significant insight into the crystal growth processes. Formation of nanocrystals is characterized by continuous, comparatively slow nucleation and fast crystal growth occurring on a time scale of seconds. Although nucleation and growth are not separated from each other, a significant narrowing of the particle size distribution during early stages results in rather monodisperse nanocrystals, before broadening of the particle size distribution occurs, as observed by complementary ex situ electron microscopy studies. Microcrystal growth is dominated by a particle−monomer addition mechanism, but indications for the operation of a coalescence process during early stages of growth have been also obtained. During later stages of microcrystal growth crystals change their shape from cubes to rhombic dodecahedra. The prepared phase-pure ZIF-8 nanoscale materials exhibit good thermal stability in air and large surface areas, which are comparable to those of large macrocrystals. Nanocrystal powders exhibit dual micro- and mesoporosity.

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

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

A beaded collar for dual micro GPS/VHF transmitter attachment to nutria

Abstract We report on the development of an approximately 85-g beaded collar for dual micro GPS/VHF transmitter attachment to semi-aquatic nutria (Myocastor coypus). Prototype collars were tested on captive nutria and refined during field trials. Central to the design was novel use of the VHF transmitter antenna as a collar. A circular collar was formed by passing the 44-cm antenna cable through a pre-made hole in the transmitter, leaving an approximately 16-cm upright antenna. GPS units were mounted separately via a hole in the base of each unit. For good satellite contact, GPS units (∼28 g) were maintained at the nape of the neck by counterbalance of the heavier VHF transmitters (∼50 g) positioned under the neck. To reduce friction, we lined the collar with alternate-sized plastic and, later, more durable nylon beads. The final collar configuration was worn for approximately 1 month deployments with only minor neck abrasion; one collar was worn successfully for 5 months. Foot entanglement remained the greatest risk of injury from the collar. By fitting collars tightly, we reduced the incidence of foot entanglement to 2 of 33 deployments (6%). Successful GPS tracks were acquired on 29 of 33 deployments (88%).

Loop Heat Pipes for Cooling Systems of Servers

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Loop heat pipes (LHPs) are exceptionally efficient heat-transfer devices that employ a closed loop evaporation-condensation cycle that can be used to cool densely packed electronic systems that reject large quantities of heat, including computers and their central processing units (CPUs). Tests were carried out on miniature ammonia LHPs with a CPU thermal simulator using different ways of condenser cooling. The possibility of maintaining the cooled object temperatures between 40<formula formulatype="inline"><tex Notation="TeX">$^\circ{\rm C}$</tex></formula> and 70<formula formulatype="inline"><tex Notation="TeX">$^\circ{\rm C}$</tex></formula> with heat load changing from 100 to 320 W was demonstrated. Subsequent tests of these devices in a 1U computer with dual core advanced micro devices Opteron CPUs, dissipating between 95 and 120 W, have confirmed the advantages and heat transfer efficiency of LHP-based cooling systems used to cool CPU in 1U chassis. </para>

Three-dimensional carbon nanowall field emission arrays

This letter reports on the fabrication of regular arrays of three dimensional graphitic structures, by growing carbon nanowalls on forests of conical Si microspikes. The high field enhancement achieved by this hierarchical growth process indicates a potential for electron emission applications. Experiments show that the field emission performance and long-term stability of the structures is by far superior to that of planar carbon nanowall mats and comparable to that reported for optimized carbon nanotube based emitters. The improved field emission properties of the fabricated arrays are attributed to the dual micro and nanomorphology of the emitters, involving a two-scale enhancement process.

Numerical and experiment analysis of nanosecond pulsed laser drilling with dual frequency

Nanosecond pulsed laser drilling is one of the most common material removal processes. Dual focus laser micro drilling is high aspect ratio micro drilling techniques. Tan et al. (2003) proposed the concept of dual focus with dual frequency femtosecond laser micro drilling on PMMA. An investigation of dual frequency micro drilling with nanosecond pulsed laser on 500 μm silicon wafer has been reported in this paper with mathematical modelling supported with experimental results. Numerical modelling has been done to study the effect of dual frequency drilling with respect to intensity distribution and resultant effect on the focused spot size. Experiments were done with single and dual wavelengths with 532 nm and 1,064 nm at different pulse energies and the results were found in reasonable match with theoretical values.

Evaluation of elastoplastic properties and fracture strength of thick diamond like carbon film by indentation

The elastoplastic properties and fracture strength of thick diamond like carbon films (with thickness over 10 µm) are studied. An indentation-based framework is outlined where the dual sharp shallow micro indentation method is employed to measure the elastoplastic properties of the film and the substrate; next, integrated acoustic emission and corrosion potential fluctuation techniques are employed to characterize the ring cracks formed due to deep spherical indentation. The fracture strength of the DLC film is obtained from parallel numerical simulations with the identified elastoplastic properties. It is found that the thick DLC film prepared by using the plasma-based ion implantation method has better fracture property than thin DLC films in previous studies.

Design and simulation of a small polygeneration plant cofiring biomass and natural gas in a dual combustion micro gas turbine (BIO_MGT)

Abstract The operation and performances of an innovative small scale polygeneration system (BIO_MGT), which combines biomass and natural gas in a micro gas turbine, has been simulated in the present work by means of a thermodynamic matching analysis. The BIO_MGT unit matches an externally fired cycle with a commercial Micro Gas Turbine (MGT, 100 kWe). A significant share of the total energy input (∼70%) is supplied by solid biomass: the remaining is provided by natural gas. The system is therefore characterised by a dual combustion system. The configuration of the plant has been conceived so to require only minor modifications to conventional MGTs and biomass furnaces available on the market. This paper describes the design of the proposed bioenergy plant as well as the structure and the application of the in-house developed simulation model AMOS which has been used as computer-aid design tool. The design activity compared various plant schemes available from literature or past research works. The thermodynamic matching analysis of the selected configuration was then carried out, with the aim to verify compressor and turbine working points and to compare these with those typical of the MGT working under standard natural gas conditions. The steady-state matching analysis was based on the performance maps (i.e. characteristic lines) of each component. The design specifications and operating range for main and sub-components were defined, and the BIO_MGT performance maps were computed. Results showed that both the turbine as well as the compressor will work within the acceptable limits, and plant performances have also been calculated at part load conditions.

Reversibly Light‐Switchable Wettability of Hybrid Organic/Inorganic Surfaces With Dual Micro‐/Nanoscale Roughness

AbstractHere, an approach to realize “smart” solid substrates that can convert their wetting behavior between extreme states under selective light irradiation conditions is described. Hybrid organic/inorganic surfaces are engineered by exploiting photolithographically tailored SU‐8 polymer patterns as templates for accommodating closely packed arrays of colloidal anatase TiO2 nanorods, which are able to respond to UV light by reversibly changing their surface chemistry. The TiO2‐covered SU‐8 substrates are characterized by a dual micro‐/nanoscale roughness, arising from the overlapping of surfactant‐capped inorganic nanorods onto micrometer‐sized polymer pillars. Such combined architectural and chemical surface design enables the achievement of UV‐driven reversible transitions from a highly hydrophobic to a highly hydrophilic condition, with excursions in water contact angle values larger than 100°. The influence of the geometric and compositional parameters of the hybrid surfaces on their wettability behavior is examined and discussed within the frame of the available theoretical models.

Bioinspired superhydrophobic poly(L‐lactic acid) surfaces control bone marrow derived cells adhesion and proliferation

The aptitude of a cell to adhere, migrate, and differentiate on a compact substrate or scaffold is important in the field of tissue engineering and biomaterials. It is well known that cell behavior can be controlled and guided through the change in micro- and nano-scale topographic features. In this work, we intend to demonstrate that special topographic features that control wettability may also have an important role in the biological performance of biodegradable substrates. Poly(L-lactic acid) surfaces with superhydrophobic characteristics were produced, based on the so-called Lotus effect, exhibiting dual micro- and nano-scale roughness. The water contact angle could be higher than 150 degrees and a value of that order could be kept even upon immersion in a simulated body fluid solution for more than 20 days. Such water repellent surfaces were found to prevent adhesion and proliferation of bone marrow derived cells previously isolated from the femurs of 6-week-old male Wistar rats, when compared with smoother surfaces prepared by simple solvent casting. Such results demonstrate that these superhydrophobic surfaces may be used to control cell behavior onto biodegradable substrates.

SU-GG-T-90: Performance of Dual Layer Micro MLC Versus Standard Single Layer MLC for IMRT Delivery

Purpose: To evaluate the performance characteristics of a first‐of‐its‐kind dual layer micro multi‐leaf collimator (DmMLC) and compare it dosimetrically with standard, single layer MLCs for use in intensity modulated radiation therapy(IMRT).Method and Materials: The DmMLC performance was studied using a cross shaped field generated by both a single layer MLC and the DmMLC. The DmMLC by Initia Medical Technologies was mounted on a Varian 600C linac unit. Film measurements were obtained using a 6 MV x‐ray beam and EDR2 film at a depth of 5 cm in solid water at 100 cm source to film distance. Film analysis was performed using the RIT V5 software. The leaf‐end transmission of the single bank and dual bank of mMLC was measured. The maximum and average leaf‐end transmissions for the cross pattern were compared for both modes of operation of the mMLC and for the standard Varian MLC.Results: The leaf‐end transmission for the single layer of the DmMLC was at its maximum 22.4% with an average value of 15.4% The transmission was reduced to a maximum of 2.4% and an average of 2.1% when both layers of the DmMLC leaves were used. Dual layer MLC provided more conformal field edge as compared to the standard single layer MLC with approximately ten fold less transmission at the leaf end. Conclusion: The results of this study indicate that the DmMLC provides more precise field shaping at field edges than the standard MLC. The DmMLC reduces the leaf‐end transmission to about 2.1%. The dual layer MLC offers more accurate IMRTdelivery to the planned target volume and spares the underlined surrounding health tissue from increased transmission and leakage dose.Conflict of Interest: The work was partially supported by a research grant from Initia RT.

Fatigue crack growth behavior of cables and steel wires for the cable-stayed portion of Runyang bridge: Disproportionate loosening and/or tightening of cables

The cable-stayed portion of the Runyang bridge has a main span of 400 m supported between towers by 52 cables on each side. The cable length and location differ contributing to different tension that would vary depending on the traffic conditions. High stresses prevail in cables near the free ends of the cantilever while the low stresses occur near quarter way of the main span and at the middle of the bridge. Such a variation has the tendency of tightening and loosening the cables in a complicated manner. The ways with which this variation would affect the damage of the cables by fatigue crack growth becomes increasingly more important in time, particularly for developing the methodology of inspection and maintenance of the bridge cables the failure of which by fatigue is likely to be location specific. One of the objectives of this work is to develop a model that can systematically determine the fatigue crack growth in pre-tensioned bridge cables that are made of stranded steel wires. The idealized cable containing 100% solidly packed wires correspond to β = 1.0 in the model. This parameter is shown to have a significant effect on the fatigue strength of the cables when using a dual scale crack growth rate relation that accounts for both macro- and micro-effects in geometry and material property. The combined influence of mean stress and stress amplitude on crack growth is shown to depend on tightening and loosening of the cables and steel wires. Variation of the tension in the cable and/or wire can be assessed by a parameter α such that α = 1 (normal tension) can serve as the reference. More and less tension correspond, respectively, to α ⩾ 1 and α ⩽ 1 . In this way, the effect of traffic on fatigue can be delineated from that without the traffic. The results are presented graphically and discussed systematically for the cables subjected to high and low stresses. This provides an overall assessment of the fatigue crack growth behavior in the Runyang cable-portion of the bridge for a total of two million cycles. In general, it can be said that Varying max. stress in cable with traffic : cable fatigue life can be enhanced and impeded, respectively, by loosening and tightening of tension in cable. Varying max. stress in cable without traffic : cable fatigue life can be enhanced and impeded, respectively, by tightening and loosening of tension in cable. Since geometric symmetry of the 52 cables cannot be satisfied exactly about the middle of the bridge, the high stresses in cable #3 is only approximately equal to that in cable #50. The same applies to the low stresses in cable #14 when compared to that in cable #28. Because of the significant difference in the fatigue life of cable #50 and #28, it is worthwhile to use a higher modulus material for cables #3 and #50 in contrast to that for cables #14 and #28. This conclusion is based on using energy density function of the dual scale micro-/macro-crack growth model. Since the results depend on the choice of the fatigue crack growth criterion, validation of engineering application should rely on minimizing contradictions and inconsistencies. Moreover, multiple criteria may be considered for the future design of bridges similar to the design of airborne vehicles that incorporate the concept of “fail safe”.

악취분별능력을 가진 자동차용 고기능 듀얼타입 집적형 유해가스 유입차단센서 개발

A dual micro gas sensor array was fabricated using nano sized <TEX>$SnO_2$</TEX> thin films which had good sensitivities to CO and combustible gases, or <TEX>$H_2S$</TEX> gas for air quality sensors in automobile. The already existed air quality sensor detects oxidizing gases and reducing gases, the air quality sensor(AQS), located near the fresh air inlet detected the harmful gases, the fresh air inlet door/ventilation flap was closed to reduce the amount of pollution entering the vehicle cabin through HVAC(heating, ventilating, and air conditioning) system. In this study, to make <TEX>$SnO_2$</TEX> thin film AQS sensor, thin tin metal layer between 1000 and <TEX>$2000{\AA}$</TEX> thick was oxidized between 600 and <TEX>$800^{\circ}C$</TEX> by thermal oxidation. The gas sensing layers such as <TEX>$SnO_2$</TEX>, <TEX>$SnO_2$</TEX>(pt) and <TEX>$SnO_2$</TEX>(+CuO) were patterned by metal shadow mask for simple fabrication process on the silicon substrate. The micro gas sensors with <TEX>$SnO_2$</TEX>(+Pt) and <TEX>$SnO_2$</TEX>(CuO) showed good selectivity to CO gas among reducing gases and good sensitivity to <TEX>$H_2S$</TEX> that is main component of bad odor, separately.

Getting better bonding at tiny interfaces

Growing demand for dual component micro parts has prompted German researchers to look closely at bonding in injection moulding…

Micro operation system based on miniature mobile robot

A newly developed micro operation system assisted by a conceptual 5-DOF (degree of freedom) macro/micro dual driven micro robot is presented. With the macro motion mode, the robot is a typical wheeled mobile robot and with the micro motion mode the robot is an inchworm robot. A manipulator is mounted on the top of robot platform for the robot accomplishing micro operation task. To navigate the robot automatically, an intelligent vision sensor system is developed. The vision system includes two parts that are the global vision system and the local vision system. The global visual system guides the robot to accomplish large workspace rapid motion. The local vision system guides the robot to accomplish small workspace precision positioning for micro operation task. Experiments show that the proposed system succeeds in providing micro operation task such as micro part gripping and assembly.

Direct imaging of the pores and cages of three-dimensional mesoporous materials

Mesostructured composite materials, with features ranging from 20 to 500 A in size, are obtained by the kinetically controlled competitive assembly of organic and inorganic species into nanostructured domains. Short-range order is limited, and long-range order is determined by weak forces such as van der Waals or hydrogen-bonding. Three-dimensional mesoporous materials obtained by removing the organic phase are of particular interest for applications such as catalysis and chemical sensing or separation, for which structural features such as cavity shape, connectivity and ordered bimodal porosity are critical. But atomic-scale structural characterization by the usual diffraction techniques is challenging for these partially ordered materials because of the difficulty in obtaining large (> 10 microm) single crystals, and because large repeat spacings cause diffraction intensities to fall off rapidly with scattering angle so that only limited small-angle data are available. Here we present a general approach for the direct determination of three-dimensional mesoporous structures by electron microscopy. The structure solutions are obtained uniquely without pre-assumed models or parametrization. We report high-resolution details of cage and pore structures of periodically ordered mesoporous materials, which reveal a highly ordered dual micro- and mesoscale pore structure.

Instrumental considerations for reliable fieldable VOC analyses

The major justification for field analysis is the production of data and information that allows decisions to be made in a timely fashion for effective mitigation and/or efficient remediation of environmental contamination. Secondary benefits include lower cost per sample, more samples analyzed per work shift, and improved monitoring for worker safety. However, all of these applications require production of field analytical data of high quality and documented consistency and integrity. These data quality requirements place special constraints on the analytical instruments that are used for field analysis. The application and analytical capabilities of a dual silicon micro fabricated gas chromatographic instrument, with dedicated microprocessor control of all analytical functions, are discussed in relation to fieldable analytical chemistry. This small, rugged and very fast instrument provides for redundancy in analytical results, or, alternatively, the use of different modes of separation to achieve a wide variety of analytical capabilities within a portable instrument configuration.