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A modeling theory is developed to predict the performance of piezoresistors which incorporate Schottky diode electrical contacts. This new theory allows the design of high performance gauges which can be fabricated using Non-Lithographically-Based Microfabrication (NLBM) techniques. These semiconductor piezoresistors can be designed in customizable sizes and fabricated in parallel in order to integrate position sensing into MEMS flexural positioners. Customizable sensing for nanopositioning platforms will enable advances in a range of nano-scale fabrication and metrology applications. A semiconductor piezoresistor with Schottky diode contacts was fabricated and attached to a titanium flexure. This device is shown to match predicted electrical performance within about 8% and to show a gauge factor of 116, within 2% of the predicted value. Optimized performance limits for Schottky diode semiconductor piezoresistors are identified to be about 127 dB full noise dynamic range for a quarter bridge over a 10 kHz sensor bandwidth on a 600 μm width titanium flexure, making them ideal for sensing on meso-/micro-scale flexural positioners. Methods are suggested for achieving the performance limits indicated above and the impact of these methods on the sensor dynamic range are studied. • A new model is presented for nonlinear semiconductor piezoresistors, and enable them to be analyzed using the standard optimization framework. • The model incorporates voltage drops, excess resistances, and barrier-based flicker noise, which apply to a wide range of gauge materials. • A gauge is fabricated and the gauge performance is shown to match the modeled performance within 2%. • The optimization theory is used to suggest performance capabilities and limitations of customized silicon piezoresistors. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a method to fabricate high purity, single chirality carbon nanotube (CNT) based sensor systems. Ultracentrifugation is initially used to create an 85% pure (6,5) CNT sample. This 85% pure sample has a gauge factor of −22.7±0.5 which is significantly lower than the predicted gauge factor of 57 for a pure (6,5) CNT. However, this measured gauge factor closely matches the predicted gauge factor for the measured distribution of chiralities in the 85% pure sample. This indicates at a small number of impurities in the sensor can have a large effect on the strain sensitivity of the sensor. In order to increase the gauge factor of the 85% pure (6,5) CNT sample, an electrical breakdown technique is used to remove the low resistance and low gauge factor CNTs from the sensor. Using this technique it is possible to increase the gauge factor of the CNT-based piezoresistive sensor from −22.7±0.5 to 34±1. This result indicates that the majority of the impurities in the sensor can be removed during the fabrication process using the electrical breakdown technique. [Copyright &y& Elsevier]

Abstract: Early stage design of precision flexure systems that utilize strain-based displacement sensing is difficult due to the strong coupling between the mechanical and sensing subsystems. Traditional tools for flexure system and compliant mechanism synthesis are not capable of simultaneously optimizing the mechanical and sensing subsystems. The building block synthesis approach developed in this work is the only tool capable of designing compliant mechanisms with integrated strain based sensing. Building block modeling allows for rapid synthesis and vetting of concepts. This approach also allows the designer to determine concept feasibility, identify performance limits and tradeoffs, and obtain 1st order estimates of flexure geometry. In short, this method enables one to find an optimal design and set first order design parameters. The utility of the building block approach is detailed in a case study detailing the synthesis and modeling of three different one degree-of-freedom translational stages that are all derived from the series and parallel addition of fixed-guided cantilever beam building blocks. [Copyright &y& Elsevier]

Abstract: The creation of new technology for high-throughput nanomanufacturing is necessary to realize the full potential of some nano-technological products. Here, we present the preliminary design and manufacture of a precision machine for enabling high-throughput nanomanufacturing processes in a laboratory environment. An error analysis and rate analysis for implementing Dip Pen Nanolithography (DPN), a scanning-probe-based nanomanufacturing process, are used to generate detailed machine functional requirements. A deterministic process is then used to design or select each machine element; standard machine elements and easily manufactured components are used when possible to achieve a low-cost design. The machine is capable of operating with an accuracy and repeatability in the range of hundreds of nanometers, with a thermal stability in the tens of nanometers, thus exceeding the performance requirements for DPN as well as the capabilities of current technology. In a manufacturing environment, the machine could implement DPN at a rate which is almost two orders of magnitude faster than current technology. Multiple machines could also be used for parallel processing and increased production rate to make a nanomanufacturing process economically viable. [Copyright &y& Elsevier]

Abstract: In this paper we introduce the principles necessary to synthesize the complete body of serial flexure system concepts, which satisfy desired design requirements using Freedom and Constraint Topologies (FACT). FACT utilizes a comprehensive library of geometric shapes that represent regions were constraints may be placed for synthesizing flexure systems that possess designer-specified degrees of freedom (DOFs). Prior to the theory of this paper, FACT was limited to the synthesis of parallel flexure systems only. The ability to synthesize serial flexure systems is important because serial flexure systems (i) may possess DOFs not accessible to parallel flexure systems, (ii) exhibit larger ranges of motion, and (iii) enable cancellation of parasitic errors. Geometric shapes that represent motions only accessible to serial flexure systems have been derived and added to the existing body of FACT shapes initially intended for parallel flexure synthesis only. Systematic rules and guidelines have been created that help designers use these shapes to generate every parallel and serial flexure concept that satisfies the desired functional requirements. We demonstrate how to use these shapes to utilize or avoid underconstraint in serial flexure synthesis. A serial flexure system is designed that interfaces the lead screw of a lathe to the carriage that it drives as a case study to demonstrate the theory of this paper. [Copyright &y& Elsevier]

Abstract: In this paper we introduce a visual approach for placing actuators within multi-axis parallel flexure systems such that position and orientation errors are minimized. A stiffness matrix, which links twists and wrenches, is used to generate geometric shapes that guide designers in selecting optimal actuator locations and orientations. The geometric shapes, called actuation spaces, enable designers to (i) visualize the regions wherein actuators should be placed so as to minimize errors, (ii) guide designers in selecting these actuators to maximize the decoupling of actuator inputs, and (iii) determine actuator forces and displacements for actuating specific degrees of freedom. These new principles, the means to practice them, and a comparison of theory verses measured behavior, are demonstrated within a case study. [Copyright &y& Elsevier]

Abstract: In this paper we introduce a new design principle, and complementary geometric entities, that form the basis for a new approach to the synthesis of multi-degree of freedom, purely parallel precision flexure systems. This approach – Freedom and Constraint Topology (FACT) – is unique in that it is based upon sets of geometric entities that contain quantitative information about a flexure system''s characteristics. A first set contains information about a flexure system''s degrees of freedom (its freedom topology) and a second set contains information about the flexure system''s topology (its constraint topology). These sets may be used to visualize the quantitative relationships between all possible flexure designs and all possible motions for a given design problem. We introduce a new principle – complementary topologies – that enables the unique mapping of freedom and constraint spaces. This mapping makes it possible to visualize and determine the general shape(s) that a viable parallel flexure system concept must have in order to permit specified motions. The shapes contain all of the relevant quantitative information that is needed to rapidly sketch early embodiments of complex parallel flexure system concepts. These shapes may then be used to rapidly synthesize a multiplicity of flexure system concepts that have (a) independent rotational and/or linear motions, (b) coupled linear and rotational motions, and (c) redundant constraints that permit the desired motions while improving stiffness, load capacity and thermal stability. This enables early-stage flexure system design via “paper and pencil sketches” without undue complications that arise when one focuses upon detailed mathematical treatments that are better-suited for optimization rather than visualization and synthesis. [Copyright &y& Elsevier]

Abstract: In this paper we use the Fourier transform to model and simulate the three-dimensional magnetic field created by finite, planar permanent magnet arrays that are Fourier-transformable and possess vertical magnetization. This approach captures the three-dimensional characteristic of the fields, including the field components near the ends of the array. These end effects are important in small-scale precision actuators where geometric constraints preclude the use of larger finite arrays that emulate the behavior of infinite arrays. We demonstrate how to model and compute the field characteristics along a plane using two-dimensional Fast Fourier transforms. Model predictions are compared with analytical solutions for a simple prototype magnet array, measured values of a magnet array''s flux density, and a meso-scale actuator''s behavior. The difference between measured and predicted values is less than 5%. [Copyright &y& Elsevier]

Abstract: This paper introduces a moving groove fixture which can be operated in two modes; as (1) a precision fixture or (2) a six-axis nanopositioner. Actuators and flexure bearings are integrated within the structural loop of the fixture, thereby enabling controlled changes in fixtured orientation and position while retaining high fixture stiffness. The combination of positioner and fixture characteristics enables one to adjust the fixtured position/orientation and then repeatably fixture about that position/orientation. Models of the fixture''s six-axis kinematic characteristics and stiffness were generated and used to design a prototype. [Copyright &y& Elsevier]

Abstract: The kinematics, stiffness, and repeatability of a moving groove, dual-purpose positioner-fixture were determined experimentally. A dual-purpose positioner-fixture is an alignment device that may be operated in a fixture mode or a six-axis nanopositioning mode. When operated in fixture mode, experiments show standard deviation in repeatability of 11, 11, and 38nm in x, y, and z; and 0.7, 0.3, and 0.3μrad in θ x , θ y , and θ z . The stiffness characteristics were shown to match predictions within 5%. When operated in nanopositioner mode, the device demonstrated 4nm resolution and a range, of 40μm×40μm×80μm in translation and 800μrad×800μrad×400μrad in rotation. The fixture possesses a load capacity of 450N and a natural frequency of 200Hz when the fixture is preloaded to 225N. [Copyright &y& Elsevier]

Abstract: This paper presents the design of a small-scale nanopositioner, the μHexFlex, which is comprised of a six-axis compliant mechanism and three pairs of two-axis thermo-mechanical micro-actuators. In this paper, we cover the modeling, design and fabrication of the μHexFlex. Specific attention is given to: (1) the use of constraint-based design in generating the compliant mechanism design, (2) the modeling of the actuators, and (3) the system model which links the actuator input and mechanism response. The measured, quasi-static performance of a 3mm diameter prototype shows a maximum range of 8.4μm×12.8μm×8.8μm and 19.2mrad×17.5mrad×33.2mrad (1.1°×1.0°×1.9°). Experimental results indicate that a constant mechanical/electrical material property system model may be used to predict the position and orientation over a range of 3.0μm×4.4μm×3.0μm and 6.3mrad×6.3mrad×8.7mrad (0.36°×0.36°×0.5°). The dynamic characteristics of the device were investigated experimentally. Experimental results show a lowest natural frequency of 4kHz. The resolution characteristics of the device have been measured at 1Å/mV. The device was created using deep reactive ion etching (DRIE). Bulk fabrication costs are estimated at less than $ 2 per device. [Copyright &y& Elsevier]

Abstract: This paper introduces an eccentric ball–shaft kinematic fixture which is capable of six-axis alignment corrections and thereby improved fixture accuracy. A kinematic model for an eccentric ball–shaft fixture was developed and used to simulate the effect of: (1) tolerances, (2) actuation errors and (3) bearing run out on fixture accuracy. The kinematic model and these errors were used to determine when it is practical to use the technology to improve fixture accuracy. The kinematic model was used to design a prototype whose performance matched the kinematic model to within 10%. Diagnosis of experimental data indicates that differences between theory and data may be explained through statistical analysis of error sources. The stabilized 1σ repeatability of the prototype was measured at better than 1.9μm/3.6μrad. [Copyright &y& Elsevier]

This paper presents the design of a novel, low-cost nano-manipulator which uses a six-axis compliant mechanism which is driven by electromagnetic actuators. The mechanism''s monolithic, planar geometry is easily fabricated via planar manufacturing processes, enables compact packaging and incorporates a flexure mechanism for achieving small transmission ratios. The manipulator tolerates ±1mm actuator misalignment with less than 0.1% full-scale position error. Measurements over a 100nm × 100nm × 100nm work volume show resolution better than our measurement capability of 5nm and open-loop parasitic errors less than 5nm. Measurements over a 100μm × 100μm × 100μm work volume show open loop errors less than 0.2% full-scale. The mechanism''s equilateral symmetry and planar geometry make it possible to limit thermal drift in position and orientation to less than 23nm and 4μrad over a 30min start up period. The nano-manipulator, built at US$ 2000 cost (excludes electronics), is used as an ultra-precision fiber optic aligner. [Copyright &y& Elsevier]

A quasi-kinematic coupling (QKC) is a fixturing device that can be used to make low-cost assemblies with sub-micron precision and/or sealing contact. Unlike kinematic couplings that form small-area contacts between mating balls in v-grooves, QKCs are based on arc contacts formed by mating three balls with three axisymmetric grooves. Though a QKC is technically not an exact constraint coupling, proper design of the contacts can produce a weakly over constrained coupling that emulates an exact constraint coupling. This paper covers the practical design of QKCs and derives the theory that predicts QKC stiffness. A metric used to minimize over constraint in QKCs is presented. Experimental results are provided to show that QKCs can provide repeatability (1/4 μm) that is comparable to that of kinematic couplings. [Copyright &y& Elsevier]

Abstract: Piezoresistive sensing systems have characteristics that enable them to act as fine-resolution, high-speed force and displacement sensors within MEMS and other small-scale systems. High-performance piezoresistive sensing systems are often difficult to design due to tradeoffs between performance requirements, e.g. range, resolution, power, bandwidth, and footprint. Given the complexity of the tradeoffs, traditional approaches to system design have primarily focused upon optimizing a few, rather than all, elements of the sensing system. This approach leads to designs that underperform the sensors optimized range and resolution by as much as two orders of magnitude. In this paper, we present a general systems approach that enables rapid optimization of all elements via a model that incorporates the behavior, noise and sensitivity associated with each element of the sensing system. The model is presented in a manner that makes the underlying principles and application accessible to a broad community of designers. The utility of the model is demonstrated via an example wherein design parameters are altered to maximize dynamic range. [Copyright &y& Elsevier]