Search

Regulatory T (Treg) cells play an important role in immune homeostasis by inhibiting cells within the innate and adaptive immune systems; therefore, the stability and immunosuppressive function of Treg cells need to be maintained. In this study, we found that the expression of insulin receptor substrate 1 (IRS1) by Treg cells was lower than that by conventional CD4 T cells. IRS1-overexpressing Treg cells showed the downregulated expression of FOXP3, as well as Treg signature markers CD25 and CTLA4. IRS1-overexpressing Treg cells also showed diminished immunosuppressive functions in an in vitro suppression assay. Moreover, IRS1-overexpressing Treg cells were unable to suppress the pathogenic effects of conventional T cells in a transfer-induced colitis model. IRS1 activated the mTORC1 signaling pathway, a negative regulator of Treg cells. Moreover, IRS1 destabilized Treg cells by upregulating the expression of IFN-γ and Glut1. Thus, IRS1 acts as a negative regulator of Treg cells by downregulating the expression of FOXP3 and disrupting stability.

Th9 cells preferentially produce IL-9 and participate in allergic responses and asthma. Differentiation of Th9 cells is induced by IL-4 and TGF-β, and then the cells are amplified by OX40 signals. The transcription factors PU.1, IRF4, and BATF are required for Th9 differentiation. BATF3 is an AP-1 family transcription factor that is highly homologous to BATF; however, its role in Th9 cells is poorly defined. Here, we show that OX40 signaling induced the expression of Batf3 and that its overexpression in the presence or absence of OX40 signaling increased the expression of IL-9 in Th9 cells. BATF3 physically interacted with IRF4 and was bound to the Il9 locus. A transient reporter assay revealed that the BATF3–IRF4 complex induced Il9 promoter activity. BATF3 rescued Il9 expression and restored the capacity to induce the airway inflammation in Batf KO Th9 cells. Thus, BATF3 itself is sufficient for the induction of Th9 cell differentiation and can substitute for BATF during Th9 cell differentiation., Immunology: fanning the fires of airway inflammation A protein that regulates gene expression in immune cells may contribute to airway inflammation in asthma and allergies. A subset of immune cells known as Th9 cells plays a prominent role in these respiratory disorders, and researchers led by Gap Ryol Lee at Sogang University in Seoul, South Korea, set out to characterize signaling mechanisms that promote Th9 production. They focused specifically on a protein called BATF3, which regulates genes responsible for maturation of a variety of other immune cell types, but whose role with regard to Th9 is poorly understood. They determined that BATF3 has a potent effect in terms of inducing Th9 cell activity, and can even take the place of another known Th9-inducing protein. These findings could assist in the development of treatments that keep airway-constricting inflammation in check.

Recently, as the practical application of deep learning has become possible, research on the problems pertaining to intrusion detection has increased.

Regulatory T (Treg) cells play an essential role in maintaining immune homeostasis, but the suppressive function of Treg cells can be an obstacle in the treatment of cancer and chronic infectious diseases. Here, we identified the homeobox protein Hhex as a negative regulator of Treg cells. The expression of Hhex was lower in Treg cells than in conventional T (Tconv) cells. Hhex expression was repressed in Treg cells by TGF-β/Smad3 signaling. Retroviral overexpression of Hhex inhibited the differentiation of induced Treg (iTreg) cells and the stability of thymic Treg (tTreg) cells by significantly reducing Foxp3 expression. Moreover, Hhex-overexpressing Treg cells lost their immunosuppressive activity and failed to prevent colitis in a mouse model of inflammatory bowel disease (IBD). Hhex expression was increased; however, Foxp3 expression was decreased in Treg cells in a delayed-type hypersensitivity (DTH) reaction, a type I immune reaction. Hhex directly bound to the promoters of Foxp3 and other Treg signature genes, including Il2ra and Ctla4 , and repressed their transactivation. The homeodomain and N-terminal repression domain of Hhex were critical for inhibiting Foxp3 and other Treg signature genes. Thus, Hhex plays an essential role in inhibiting Treg cell differentiation and function via inhibition of Foxp3.

The intrinsic features of Internet networks lead to imbalanced class distributions when datasets are conformed, phenomena called Class Imbalance and that is attaching an increasing attention in many research fields. In spite of performance losses due to Class Imbalance, this issue has not been thoroughly studied in Network Traffic Classification and some previous works are limited to few solutions and/or assumed misleading methodological approaches. In this study, we propose a method for generating network attack traffic to address data imbalance problems in training datasets. For this purpose, traffic data was analyzed based on deep packet inspection and features were extracted based on common traffic characteristics. Similar malicious traffic was generated for classes with low data counts using Wasserstein generative adversarial networks (WGAN) with a gradient penalty algorithm. The experiment demonstrated that the accuracy of each dataset was improved by approximately 5% and the false detection rate was reduced by approximately 8%. This study has demonstrated that enhanced learning and classification can be achieved by solving the problem of degraded performance caused by data imbalance in datasets used in deep learning based intrusion detection systems.

This manuscript reviews the developments made in design and fabrication of piezoelectric microgenerators and presents a method for making a comparative study within various vibration energy harvesting mechanisms. Current generation vibration energy harvesters have power density in the range of 0.8 microW/mm3. The manuscript also reports our results on synthesis of barium titanate (BT) thin films for MEMS (micro-electromechanical systems) based energy harvester. BT sol-gel was synthesized by aqueous process using barium acetate and titanium bis (ammonium lacto) dihydroxide with PVP (Polyvinylpyrrolidone). After optimizing the annealing temperature and time, textured BT films with 600 nm thickness were obtained on (111) Pt/Ti/SiO2 wafer. A MEMS fabrication process flow was designed to produce microcantilever chips from BT films constituting 6 cantilevers connected in series with an interdigital electrode pattern. We also present some concepts for further improvement of the power density of vibration energy harvesters by incorporating 3-D structure, magnetoelectric material, and a multimodal scheme.

In this study, we report results on a piezoelectric- material-based mechanical energy-harvesting device that was fabricated by combining laser machining with microelectronics packaging technology. It was found that the laser-machining process did not have significant effect on the electrical properties of piezoelectric material. The fabricated device was tested in the low-frequency regime of 50 to 1000 Hz at constant force of 8 g (where g = 9.8 m/s(2)). The device was found to generate continuous power of 1.13 microW at 870 Hz across a 288.5 kOmega load with a power density of 301.3 microW/cm(3).

This letter reports the effect of the A-site doping (2, 4, and 6 mol% Bi and Li) on the piezoresistance phenomenon in La0.8Sr0.2MnO3 (LSMO) polycrystalline ceramics. The fractional change in resistivity was found to be nominal for Li-modified samples but samples modified with 4 and 6 mol% Bi2O3 exhibited 1.8% and 2.3% fractional change in resistivity $$ [(\rho _{o} - \rho _{\sigma } )/\rho _{o} ] $$ at 19.2 MPa which is significantly higher than that for pure LSMO. The enhancement in piezoresistive phenomenon is attributed to distortion of Mn–O bond due to substitution of smaller ion on to La-site. All the samples showed a sudden increase in resistivity with applied stress in the range of 0.5–2 MPa and the behavior was found to saturate as the magnitude of applied stress increases. Magnetic measurements as a function of field and temperature were conducted to confirm the A-site substitution.

Robotic skins with multi-modal sensors are necessary to facilitate better human-robotic interaction in non-structured environments. Integration of various sensors, especially onto substrates with non-uniform topographies, is challenging using standard semiconductor fabrication techniques. Printing is seen as a technology with great promise that can be used for sensor fabrication and integration as it may allow direct printing of different sensors onto the same substrate regardless of topology. In this work, we investigate Electro-Hydro-Dynamic (EHD) printing, a method that allows printing of micron-sized features with a wide range of materials, for fabricating pressure sensor arrays using Poly(3,4- ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS). Fabrication of such sensors has been achieved by prepatterning gold or platinum metallized interdigitated comb electrode arrays on a polyimide substrate, with three custom made PEDOT:PSS based inks printed directly onto the electrode arrays. These three inks include a formulation of PEDOT:PSS and NMP; PEDOT:PSS, PVP, and NMP; and PEDOT:PSS, PVP, Nafion, and NMP. All these inks were successfully printed onto sensor elements. The initial results of bending-induced strain tests on the fabricated sensors display that all the inks are sensitive to strain. This confirms their suitability for pressure and strain sensor applications; however, the behavior of each ink; including sensitivity, linearity, and stability; is unique to the type.

Human-robot interaction can be made more sophisticated and intuitive if the entire body of a robot is covered with multimodal sensors embedded in artificial skin. In order to efficiently interact with humans in unstructured environments, robotic skin may require sensors such as touch, impact, and proximity. Integration of various types of sensors into robotic skin is challenging due to the topographical nature of skin. Printing is a promising technology that can be explored for sensor integration as it may allow both sensors and interconnects to be directly printed into the skin. We are developing Electrohydrodynamic (EHD) inkjet printing technology in order to co-fabricate various devices onto a single substrate. Using strong applied electrostatic forces, EHD allows the printing of microscale features from a wide array of materials with viscosities ranging from 100 to 1000cP, highly beneficial for multilateral integration. Thus far we have demonstrated EHD’s capability at printing patterns of Poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate) for pressure sensor applications, generating patterns with modified commercial photoresist for mask-less lithography, and obtaining ZnO microstructures for direct device printing. Printed geometries range from a few tens of microns to millimeters. We have used inks with viscosities ranging from 230 to 520cp and from non-conductive to 135μS/cm. These results clearly show that the EHD is a promising multi-material printing platform and would be an enabling technology that can be used to co-fabricate various devices into robotic skin.

Future robot skin will consist of massive numbers of sensors embedded in flexible and compliant elastomer substrate. To test and characterize pressure-sensitive skin prototypes, we have built an experimental testbed capable of applying controlled loading profiles, using the data to create reduced-order models of skin sensors for simulation and control. Measurement data from a load applicator and embedded taxel is acquired using National Instruments real-time control technology. Reduced-order models were proposed to relate the load applied to robot skin to the load sensed by the embedded taxel. Experiments for soft skin material characterization and taxel characterization were also undertaken with the testbed to better understand their nonlinear behavior. With this setup current and future skin sensor designs undergoing a range of loading profiles can be tested and modeled.

Reconfigurable robotic systems can be adapted to different tasks or environments by reorganizing their mechanical configurations. Such systems have many redundant degrees of freedom in order to meet the combined demands of strength, rigidity, workspace kinematics, reconfigurability, and fault tolerance. In order to implement these new generations of robotic system, new approaches must be considered for design, analysis, and control. This paper presents an efficient distributed computational scheme which computes the kinematics, dynamics, redundancy resolution, and control inputs for real-time application to the control of the Tetrobot modular reconfigurable robots. The entire system is decomposed into subsystems based on a modular approach and Newton's equations of motion are derived and implemented using a recursive propagation algorithm. Two different dynamic resolution of redundancy schemes, the centralized Jacobian method and the distributed virtual force method, are proposed to optimize the actuating forces. Finally, distributed dynamic control algorithms provide an efficient modular implementation of the control architecture for a large family of configurations.

Stainless steel castings are used in pipes and valves subjected to high pressure and temperatures. The primary coolant system of a nuclear power plant is made of a stainless steel casting and the operating temperatures are in the range of 290–330°C. If the coolant system is exposed to these temperature ranges for a long period, it may be possible to experience degradation of the material. The present investigation is concerned with the degradation characteristics of CF8M (cast duplex stainless steel), exposed to the thermal and σ-phase degradation temperatures, 430 and 700°C, respectively. After the CF8M specimens are held 100–3600 h at 430°C for the thermally degraded specimens and maintained 20 min to 150 h at 700°C for the σ-phase degraded specimens, respectively, all specimens are water quenched. Each specimen of the thermally and σ-phase degraded materials is classified into five classes depending on the holding time at the given temperatures. In order to investigate the characteristics of degradation, microstructure, micro Vickers hardness, tensile, impact tests, and fatigue crack growth tests are performed for each class of the specimens. From the present investigation the following results were obtained: (1) the difference between the thermally and σ-phase degraded specimens can be distinguished through their microstructures, (2) hardness and tensile strength are increased with degradation, while elongation, reduction area, and impact energy are decreased by increasing the degradation, (3) the fatigue crack growth rate (FCG) of the σ-phase degradation at 700°C is larger than that of the thermally degraded specimens, and (4) the FCG for both thermally and σ-phase degraded specimens are larger than those of the virgin (nondegraded) specimens.

This paper focuses on robotic technologies and operational capabilities of multiscale robots that demonstrate a unique class of Microsystems with the ability to navigate diverse terrains and environments. We introduce two classes of robots which combine multiple locomotion modalities including centimeter scale Discrete and Continuous robots which are referred here by D-Starbot and C-Starbot, respectively. The first generation of the robots were obtained to allow rapid shape reconfiguration and flipping recovery to accomplish tasks such as lowering and raising to dexterously go over and under obstacles, deform to roll over hostile location as well as squeezing through opening smaller than its sizes. The D-Starbot is based on novel mechanisms that allow shape reconfiguration to accomplish tasks such as lowering and raising to go over and under obstacles as well as squeezing through small voids. The CStarbot is a new class of foldable robots that is generally designed to provide a high degree of manufacturability. It consists of flexible structures that are built out of composite laminates with embedded microsystems. The design concept of C-Starbot are suitable for robots that could emulate and combine multiple locomotion modalities such as walking, running, crawling, gliding, clinging, climbing, flipping and jumping. The first generation of C-Starbot has centimeter scale structure consisting of flexible flaps, each being coupled with muscle-like mechanism. Untethered D-Starbot designs are prototyped and tested for multifunctional locomotion capabilities in indoor and outdoor environments. We present foldable mechanism and initial prototypes of C-Starbot capable of hopping and squeezing at different environments. The kinematic performance of flexible robots is thoroughly presented using the large elastic deflection of a single arm which is actuated by pulling force acting at variable angles and under payload and friction forces.

We evaluated the efficacy and safety of chemotherapy with S-1/CDDP for advanced and recurrent gastric cancer at Fuchu Hospital.The participants were 24 patients treated at our hospital. S-1 was given orally at 80 mg/m/2 for days 1-21, and 60 mg/m2 of CDDP was administered on day 8, followed by a 2-week rest period, within a 5-week course.Results were rated as a partial response in 12 cases and a stable response in 4 cases. The response rate was 50% (12/24), and median survival time was 273 days. The total incidence of grade 3 or greater adverse reactions including leucopenia, neutropenia, anemia, general fatigue, and eruption, was 25% (6/24).The combination of S-1/CDDP therapy appears to be highly efficacious and safe and showed promise as a useful treatment strategy, even in an outpatient clinic.

This paper presents the statistical formulation of misalignments of optical components. As a case study, sensitivity analysis is performed to evaluate the optical performance of an assembled Fourier Transform (FT) microspectrometer. Precision alignment of optical components is a critical factor to achieve high sensitive measurement. Positional and angular misalignments of optical components are propagated and accumulated from one part to another as the beam is delivered. Optical paths are modeled as kinematic variables of a linked chain, and its propagation is calculated using forward kinematics with homogeneous transform matrices. This approach not only formulates the deviation of beam paths as traditional optics do, but also accommodates statistical variables to represent the mean and variance of kinematic errors. With the assumption of Gaussian distribution of the errors, the statistical equation was linearly propagated. The beam deviation was further combined with a light coupling model at the detector to evaluate the degradation of optical. Its prototype and experimental results were also reported.

This paper presents the design, analysis, and fabrication of an array of microflap actuators that can produce a substantial aerodynamic force for course corrections of Micro Air Vehicles (MAVs) and low speed projectiles. In the past, several actuation principles, including microjet, magnetic and bubble actuators, and flapping wings have been proposed, and had varying degrees of success. In this paper, we discuss the benefits and drawbacks of past attempts, and the technology that can be used to address the microflap steering problem. We propose a hybrid microflap actuation scheme that combines two types of actuators including: 1) a MEMS fabricated "active" microactuator connected to a microflap, and 2) a "passive" fluidic channel system that harvests the potential energy in the high pressure field on the leading edge of the MAV or high speed projectile to achieve a desired deflection. An array of microflap actuators was prototyped using silicon MEMS fabrication and microassembly. A Silicon On Insulator (SOI) wafer with 100 micron thick device layer was used to as a substrate material to fabricate microflap structures with springs. Front and back side DRIE process was used to etch and release the microstructures including microflaps. Then, the microactuator was assembled on top of the microflap. The static and dynamic behaviors of a microflap were measured using a laser displacement sensor and were compared to the analytic model. In the near future, a prototyped microflap will be tested inside of a wind tunnel to measure the lift and drag at various air speeds.

This paper presents a new method that evaluates the manufacturability of microoptical systems. A statistical, kinematic link model is applied to compute the deviations of optical paths due to the positional and angular misalignments of optical components. The deviation of optical paths is a main source that deteriorates the performance of an optical system, hence it is very important to quantify how misalignments accumulate and propagate from one component to another. This method was applied to evaluate the optical performance of an assembled, chip-scale Fourier Transform (FT) microspectrometer. The microspectrometer was prototyped by using the microassembly of heterogeneous optical components. The statistical model computes the optical paths of two beams that travel through an input fiber, a beam splitter, moving and fixed mirrors, and a detector. Its results were used to determine the tolerance budgets for the fabrication and assembly processes of micro optical components.

Heterogeneous assembly of 21/2D or 3D MEMS components is an alternate micromanufacturing route to monolithic integration or other stochastic, self-assembly approaches. This approach is deterministic (directed) and involves using microgrippers mounted on precision robots to pick-and-place microparts. In this context, the use of engineered compliance has been recently proposed as a very practical way to account for positional tolerances of the robot end-effectors and the manufacturing tolerances in the microparts. In this paper, we examine the most important tradeoffs in compliant MEMS assembly and conclude that the use of automation at these scales is qualitatively different than automation at larger scales. Whereas at the meso and macro scales, automation is often undertaken after, and often benchmarked against manual assembly, deterministic automation at the MEMS scale is a more holistic approach. This means that the designs of the assembly cell, part and end-effectors should be considered simultaneously, and that by doing so, we can automate assembly operations without the use of closed-loop feedback. To support our findings, we use several examples of micropart design and experimental results with mu3, a microrobotic workcell configured for high yield MEMS assembly.

Microgrippers based on electrothermal actuation were designed and fabricated using the deep reactive ion etching (DRIE) process with 100mum thick silicon on insulator (SOI) wafer. The design requirements are restricted to basic manipulation tasks such as pick and place, and nonprehensile manipulation. This paper explores several electrothermal end-effectors which have been fabricated for serial and parallel microassembly. The end-effectors include three main building blocks: 1) Integrated and symmetrical actuators of V and U shapes. The symmetrical expansions on Chevron and hot arms allow combination of forward translations that amplify angular motion at the tips of a gripper. 2) A joule heating element based on a resistive V-shape electrothermal actuator. In 3D microassembly, the joining of a micropart is essentially performed by providing an integrated microheater device. 3) A force or position feedback sensing block based on self-straining or electrostatic principle. The integrated sensor can be calibrated for both position and force measurements. Serial heterogeneous assembly of meso and micro-scale objects is demonstrated using a 3D microassembly station. Black-box dynamical models for microgrippers are derived using experimentally obtained data, and performance variations due to the way the microgrippers are mounted onto the robot are discussed.

Micro-Opto-electro-Mechanical Systems (MOEMS), which are MEMS integrated with photonics, share the traditional challenges of MEMS packaging with the additional issues of optical interconnects and optical surface contamination. Optoelectronic systems require signals through a package using fiber-optics, coaxial or other interconnection approaches. Precise optical component alignment and accurate thermal management is critical to achieve component and system performance capabilities. As the requirements for higher signal speeds and higher data rates grow, and as operating frequencies move to the higher GHz regions and beyond, the choice of packaging technology becomes critical. Optical MEMS packages not only have to provide electrical connections but also support high precision optics and mechanics, vital for operation of optical MEMS devices. Analogous to MEMS, packaging is also a critical path in reliability and cost of MOEMS devices. One of the commonly observed failures is the de-lamination between the chip (die) and the die attach. The focus of this paper is the development of a reliable fluxless die attachment process suitable for MOEMS assemblies with long operational life time. The reliability assessment was carried out at the Texas Microfactory™ at UT Arlington according to the MIL-STD-883F for die shear reliability.Copyright © 2007 by ASME

Microassembly is an enabling technology to build 3D microsystems consisting of microparts made of different materials and processes. Multiple microparts can be connected together to construct complicated in-plane and out-of-plane microsystems by using compliant mechanical structures such as micro hinges and snap fasteners. This paper presents design, fabrication, and assembly of an active locking mechanism that provides mechanical and electrical interconnections between mating microparts. The active locking mechanism is composed of thermally actuated Chevron beams and sockets. Assembly by means of an active locking mechanism offers more flexibility in designing microgrippers as it reduces or minimizes mating force, which is one of the main reasons causing fractures in a microgripper during microassembly operation. Microgrippers, microparts, and active locking mechanisms were fabricated on a silicon substrate using the deep reactive ion etching (DRIE) processes with 100-um thick silicon on insulator (SOI) wafers. A precision robotic assembly platform with a dual microscope vision system was used to automate the manipulation and assembly processes of microparts. The assembly sequence includes (1) tether breaking and picking up of a micropart by using an electrothermally actuated microgripper, (2) opening of a socket area for zero-force insertion, (3) a series of translation and rotation of a mating micropart to align it onto the socket, (4) insertion of a micropart into the socket, and (5) deactivation and releasing of locking fingers. As a result, the micropart was held vertically to the substrate and locked by the compliance of Chevron beams. Microparts were successfully assembled using the active locking mechanism and the measured normal angle was 89.2°. This active locking mechanism provides mechanical and electrical interconnections, and it can potentially be used to implement a reconfigurable microrobot that requires complex assembly of multiple links and joints.

This paper presents a design of micropump, which is an assembly of silicon micromachined actuator with a polymer tube diaphragm. The pump actuation principle is electrothermal expansion of a silicon V-beam structure, and its expansion is amplified through a lever structure to create greater diaphragm stroke as presented in J. Sin et al. (2004). Diffuser/nozzle structures are applied to direct the flow from an inlet to outlet port while the actuator provides pumping motion. Deep RIE (reactive ion etching) process is used to fabricate the pump structure on a SOI (silicon on insulator) wafer. Polymer tube is fabricated from Parylene conformal deposition process using a DRIE silicon mold and the tube structure is assembled with the silicon actuator module. FEM analysis is performed on the tube structure and the simulation results show that the stroke of the tube diaphragm becomes much smaller than original actuator stroke, mainly due to the constrained tube geometry in silicon structure. When the tube stroke is combined with the diffusion/nozzle flow mechanism, the resultant flow rate of the pump was about 160nl/min, which will be suitable for low flow rate and high precision applications. Further study is on going to build prototype of the pump.

The performance of any micro-comronent affects the overall performance of the system especially in the micro-level. In this research work, the thermal and structural performances of microgripper based on silicon are studied. The present study is part of a larger effort in developing, modeling and characterization procedures toward understanding the behavior of microgripper. This is essential to develop better control algorithms and to facilitate the study of robot arms dynamic on gripping performance. The structural stiffness and failure of microgripper in static loading are characterized for two actuation modes: in-plane and off-plane. Moreover, building block attempts are introduced for dynamical modeling of microgripper/sensor/and environment. The electromechanical system model of sensor is experimentally identified and utilized in identifying the performance of hypothesized lumped models of microgripper.

Microassembly process plays a key role in building 3-dimensional heterogeneous microsystems. This paper presents a miniaturized Fourier transform spectrometer (FTS) implemented by combining silicon micromachining and microassembly techniques. The FTS is based on a Michelson interferometer where a scanning mirror mechanism creates an interferogram, and the recorded interferogram is converted to a spectrum by Fourier transform. The miniaturized Michelson interferometer is integrated on a microoptical bench, which is fabricated using Deep RIE (Reactive Ion Etching) process on a SOI (Silicon On Insulator) wafer. Key components of the FTS optical bench are a linear translation stage, mechanical assembly sockets, a beam splitter, and assembled mirrors. An electrothermal actuator with stroke amplification mechanisms provides the amplified scanning motion of a scanning mirror. The sockets are female mechanical flexure structures that allow a precise snap-fit assembly with micromachined silicon mirrors. The dimension of the FTS optical bench is 1cm2, and its embedded thermal actuator has a couple of V-beam structures whose beam length is 1mm. The mirrors are Deep RIE micromachined structures with reflection area 500x450μm2 and 750μm long flexure structures for pick & place assembly. The flexure structure allows large deflection so that a microgripper can pick up the mirror by inserting the gripper tip into the structure, and snap-fit assembles it into the mechanical socket of the bench. The linear translation stage generates up to 30μm scanning stroke at 22V input, which corresponds to a spectral resolution of 10nm at 775nm wavelength. While this microassembly method is designed to self-align the mirror in the socket, the mirror slightly tilts after assembly due to the slope of side wall of DRIE processed structures. The measured tilting angles of assembled mirrors range from -2.5° to 0.8° from several assembly trials. The tilting angle combined with beam divergence can cause the loss of power and resolution, spectrum shift and phase error. A He-Ne laser was used as a light source to create interferogram with the assembled microspectrometer. Formation of fringe patterns was successfully conducted with a prototype. Mirrors with a large tilting misalignment resulted in stripe pattern fringes, whereas an improved alignment generated circular pattern fringes. A detector was used to measure light power with respect to input voltage, and the displacement of a scanning mirror was measured and curve-fitted. The relationship between light power changes versus the displacement of a scanning mirror represents interferogram. Spectrum profiles showed a peak around 632nm with FWHM (Full Width Half Magnitude) 25nm approximately. While further research is on going to improve spectrum quality and microassembly technique for the integration of various components with heterogeneous materials and shapes, this approach is expected to facilitate the design and manufacturing of MOEMS from the constraints of micromachining processes.

This paper presents the design, analysis, and fabrication of a novel polymer tube embedded in-plane micropump. The key component of the proposed micropump is a Parylene polymer tube that is embedded into a silicon micromachined actuation structure. The advantages of embedding a Parylene polymer tube are biocompatibility, leakage free flow, and insulation from electrical and thermal contacts. The tube works as a diaphragm, which transfers the pumping motion from the silicon electrothermal actuators to fluid. In order to guide the design of the pump, FEM simulation was performed for structural analysis on Parylene tube and evaluation of the electrothermal actuator. Parylene was conformally deposited on the nickel coated DRIE processed silicon mold, and peeled off and two Parylene layers were bonded together to form a tube. The maximum deflection achieved from the Parylene diaphragm is 5.4μm and the computed flow rate of the pump is 160nl/min.Copyright © 2005 by ASME

In this paper we describe two modular automated microassembly systems, along with a several packaging processes that have been integrated to produce reliable and cost-effective MOEMS devices. The automated and packaging systems consists of robotics such as pick and place, insertion and fastening, machine vision and controls, and processes such as die attach, solder reflow by laser, wire bonding and seam sealing. The target MOEMS devices are intended for applications requiring a minimum twenty year shelf-life.Copyright © 2005 by ASME

This paper presents analytical, simulation and experimental results from a study of compliant insertion tasks in microassembly. Gripper compliance is desirable to compensate for positional errors and to prevent the breakage of a gripper during assembly tasks. An analytical model is derived to study the motion and force profiles during compliant insertion. Thermal bimorph microgrippers with a compliant tip are designed and fabricated using a silicon DRIE process, and are mounted on a precision motion stage. A series of micropeg manipulation tasks such as pick up, rotation, and insertion are successfully performed. Finally, a comb structure is integrated in the gripper to calculate insertion force by measuring the deflection of a gripper, which is essential for automated microassembly.

This work presents a framework of tolerance analysis of microparts in microassembly. Tolerance analysis at the micro scale has not been investigated so far even though tolerance analysis at the macro scale has extensively been investigated to improve an assembly yield. It is important to know the positional uncertainties and statistical distribution of parts before and after untethering to improve assembly yield. Positional misalignments of microparts are extracted from raw CCD images and the statistical distribution of parts variances are computed using clustering and transformation of Gaussian distribution. The distributions are not pure Gaussian in nature as might be expected. There are several location peaks found, usually centered at the fabrication location, and at the hard-stop locators.

This paper proposes a distributed control scheme for a highly redundant parallel Tetrobot mechanism. The architecture of the proposed distributed control is composed of processors dedicated to each module and a network used to communicate the information between the modules. Each processor computes the kinematics, dynamics and control input for the dedicated module using the subsystem dynamic model and the information communicated only from adjacent modules. The simulation results of set-point and tracking control are provided to demonstrate the feasibility of the proposed scheme and compared to centralized control. The results show that the controlled node reaches the desired position without a steady state error even though the convergence rate is slower than for the centralized scheme. To improve the problem caused by a local optimization technique, an iteration scheme of local optimization was also applied to obtain a global solution to generate the paths of uncontrolled nodes.

A distributed computation algorithm based on the virtual force method supports the computation of dynamic redundancy resolution for modular reconfigurable robotic systems. Such systems have many redundant degrees of freedom in order to meet the combined demands of strength, rigidity, workspace kinematics, reconfigurability, and fault tolerance. An efficient distributed computational scheme computes the kinematics, dynamics, and redundancy resolution for real-time application to the control of these systems. A potential function which depends only on the local information of adjacent nodes of the structure is introduced and applied to the Tetrobot modular reconfigurable system. Simulation results are provided to demonstrate the feasibility of the proposed distributed algorithms, and these results are compared to the centralized Jacobian method which requires global information.