Grasping and releasing agarose micro beads in water drops

The micromanipulation of micro objects is nowadays the focus of several investigations, specially in biomedical applications. Therefore, some manipulation tasks are required to be in aqueous environment and become more challenging because they depend upon observation and actuation methods that are compatible with MEMS Technology based micromanipulators. This paper describes how three grasping-releasing based tasks have been successfully applied to agarose micro beads whose average size is about 60 \u3bcm: (i) the extraction of a single micro bead from a water drop; (ii) the insertion of a single micro bead into the drop; (iii) the grasping of a single micro bead inside the drop. The success of the performed tasks rely on the use of a microgripper previously designed, fabricated, and tested

Design and fabrication of a multipurpose compliant nanopositioning architecture

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 227-241).This research focused on generating the knowledge required to design and fabricate a high-speed application flexible, low average cost multipurpose compliant nanopositioner architecture with high performance integrated sensing. Customized nanopositioner designs can be created in ~~1 week, for 30x increase in sensing dynamic range over comparable state-of-the-art compliant nanopositioners. These improvements will remove one of the main hurdles to practical non-IC nanomanufacturing, which could enable advances in a range of fields including personalized medication, computing and data storage, and energy generation/storage through the manufacture of metamaterials. Advances were made in two avenues: flexibility and affordability. The fundamental advance in flexibility is the use of a new approach to modeling the nanopositioner and sensors as combined mechanical/electronic systems. This enabled the discovery of the operational regimes and design rules needed to maximize performance, making it possible to rapidly redesign nanopositioner architecture for varying functional requirements such as range, resolution and force. The fundamental advance to increase affordability is the invention of Non-Lithographically-Based Microfabrication (NLBM), a hybrid macro-/micro-fabrication process chain that can produce MEMS with integrated sensing in a flexible manner, at small volumes and with low per-device costs. This will allow for low-cost customizable nanopositioning architectures with integrated position sensing to be created for a range of micro-/nano- manufacturing and metrology applications. A Hexflex 6DOF nanopositioner with titanium flexures and integrated siliconpiezoresistive sensing was fabricated using NLBM. This device was designed with a metal mechanical structure in order to improve its robustness for general handling and operation. Single crystalline silicon piezoresistors were patterned from bulk silicon wafers and transferred to the mechanical structure via thin-film patterning and transfer. This work demonstrates that it is now feasible to design and create a customized positioner for each nanomanufacturing/metrology application. The Hexflex architecture can be significantly varied to adjust range, resolution, force scale, stiffness, and DOF all as needed. The NLBM process was shown to enable alignment of device components on the scale of 10's of microns. 150μm piezoresistor arm widths were demonstrated, with suggestions made for how to reach the expected lower bound of 25[mu]m. Flexures of 150[mu]m and 600[mu]m were demonstrated on 4 the mechanical structure, with a lower bound of ~~50[mu]m expected for the process. Electrical traces of 800[mu]m width were used to ensure low resistance, with a lower bound of ~~100[mu]m expected for the process. The integrated piezoresistive sensing was designed to have a gage factor of about 125, but was reduced to about 70 due to lower substrate temperatures during soldering, as predicted by design theory. The sensors were measured to have a full noise dynamic range of about 59dB over a 10kHz sensor bandwidth, limited by the Schottky barrier noise. Several simple methods are suggested for boosting the performance to ~~135dB over a 10kHz sensor bandwidth, about a <1Å resolution over the 200[mu]m range of the case study device. This sensor performance is generally in excess of presently available kHz-bandwidth analog-to-digital converters.by Robert M. Panas.Ph.D

Methods and Sensors for Slip Detection in Robotics: A Survey

The perception of slip is one of the distinctive abilities of human tactile sensing. The sense of touch allows recognizing a wide set of properties of a grasped object, such as shape, weight and dimension. Based on such properties, the applied force can be accordingly regulated avoiding slip of the grasped object. Despite the great importance of tactile sensing for humans, mechatronic hands (robotic manipulators, prosthetic hands etc.) are rarely endowed with tactile feedback. The necessity to grasp objects relying on robust slip prevention algorithms is not yet corresponded in existing artificial manipulators, which are relegated to structured environments then. Numerous approaches regarding the problem of slip detection and correction have been developed especially in the last decade, resorting to a number of sensor typologies. However, no impact on the industrial market has been achieved. This paper reviews the sensors and methods so far proposed for slip prevention in artificial tactile perception, starting from more classical techniques until the latest solutions tested on robotic systems. The strengths and weaknesses of each described technique are discussed, also in relation to the sensing technologies employed. The result is a summary exploring the whole state of art and providing a perspective towards the future research directions in the sector

Development of a 3-axis MEMS magnetometer based on Lorentz force

Dissertação de mestrado em Physics Engineering, (especialização em Devices, Microsystems and Nanotechnologies)Typical magnetometers found in the magnetic fields research are highly incompatible with the massive MEMS technology industry that has been the object of study in the past years. This aspect leads to the rapid increase in production costs and reliability reduction. Furthermore, most of the magnetometers that are adapted to this technology are highly complex and with little to no adaptation to outer-space research. In this work, a novel single-axis MEMS magnetometer based on the principle of the Lorentz force capable of reading fields in the X or Y direction is designed and simulated with the description of a fabrication method to be used. This magnetometer uses an innovative design for a current-carrying-bar that’s highly adaptable to a variety of scenarios with a low 100Ω current resistance in each of its paths. An amplitude-modulated method is approached through the use of a capacitive-readout system and an off-resonance frequency of operation to achieve the detection baseline of a 1aF capacitive variation at a 20nT magnetic field. This involves the use of various mechanisms to increase the quality factor and reduce the overall stiffness of the device to increase its displacement caused by the Lorentz force. The device is also to be operated at a 500Pa atmosphere to reduce the damping and, at the same time, increase the quality factor. A thermomechanical noise below 3 /√ with a frequency of operation at around 4977 Hz was deemed necessary to adapt the design to another previously designed single-axis MEMS magnetometer capable of reading fields in the Z direction. Various simulation and design tools are used to predetermine the best properties at which the magnetometer will be operated to its highest capabilities. Through these simulations, a 50Hz bandwidth magnetometer, required for spatial research, is achieved with a capacitance variation of 1.37aF at 20nT surpassing the initial requirements. A 1.77 /√ thermomechanical noise is obtained, well below the baseline that was defined for this work. A fabrication layout was developed with all lithography masks designed, and a microfabrication process flow was devised. The microfabrication process run was partially completed and it’s still ongoing.Os magnetómetros típicos encontrados na investigação de campos magnéticos são altamente incompatíveis com a enorme indústria da tecnologia MEMS que tem sido objeto de estudo nos últimos anos. Este aspeto leva ao rápido aumento dos custos de produção e à redução da fiabilidade. Para além disso a maioria dos magnetómetros adaptados a esta tecnologia são altamente complexos e com pouca ou nenhuma adaptação à investigação espacial. Neste trabalho, um novo magnetómetro MEMS de um único eixo baseado no princípio da força de Lorentz capaz de ler campos na direção X ou Y é concebido e simulado com a descrição de um método de fabrico a ser utilizado. Este magnetómetro utiliza um desenho inovador para uma barra condutora que é altamente adaptável a uma variedade de cenários com uma baixa resistência de 100Ω em cada um dos seus caminhos. Um método de modulação em amplitude é abordado através da utilização de um sistema de leitura capacitiva e uma frequência de operação com um desvio da ressonância para alcançar a linha de base de deteção de uma variação capacitiva de 1aF para um campo magnético de 20nT. Isto envolve a utilização de vários mecanismos para aumentar o fator de qualidade e reduzir a rigidez geral do dispositivo para aumentar o deslocamento causado pela força de Lorentz. O dispositivo deve também ser operado a uma atmosfera de 500Pa para reduzir o amortecimento e, ao mesmo tempo, aumentar o factor de qualidade. Um ruído termomecânico inferior a 3 /√ com uma frequência de operação de cerca de 4977 Hz foram consideradas necessárias para adaptar o desenho a outro magnetómetro MEMS de um eixo, previamente concebido, capaz de ler campos na direção Z. Várias ferramentas de simulação e desenho são utilizadas para pré-determinar as melhores propriedades em que o magnetómetro será operado até às suas capacidades mais elevadas. Através destas simulações, um magnetómetro de 50Hz de largura de banda, necessário para a investigação espacial, é alcançado com uma variação de capacidade de 1.37aF a 20nT, ultrapassando os requisitos iniciais. É obtido um ruído termomecânico de 1.77 /√, bem abaixo da linha de base que foi definida para este trabalho. Foi desenvolvido um esquema de fabricação com todas as máscaras litográficas concebidas, e foi concebido um fluxo de processo de microfabricação. A execução do processo de microfabricação foi parcialmente concluída e ainda está em curso.This work was framed in the scope of the Project (Link4S)ustainability - A new generation connectivity system for creation and integration of networks of objects for new sustainability paradigms [POCI-01- 0247-FEDER-046122 | LISBOA-01-0247-FEDER-046122], financed by the Operational Competitiveness and Internationalization Programmes COMPETE 2020 and LISBOA 2020, under the PORTUGAL 2020 Partnership Agreement, and through the European Structural and Investment Funds in the FEDER component

Development and implementation of a deflection amplification mechanism for capacitive accelerometers

Micro-Electro-Mechanical-Systems (MEMS) and especially physical sensors are part of a flourishing market ranging from consumer electronics to space applications. They have seen a great evolution throughout the last decades, and there is still considerable research effort for further improving their performance. This is reflected by the plethora of commercial applications using them but also by the demand from industry for better specifications. This demand together with the needs of novel applications fuels the research for better physical sensors.Applications such as inertial, seismic, and precision tilt sensing demand very high sensitivity and low noise. Bulk micromachined capacitive inertial sensors seem to be the most viable solution as they offer a large inertial mass, high sensitivity, good noise performance, they are easy to interface with, and of low cost. The aim of this thesis is to improve the performance of bulk micromachined capacitive sensors by enhancing their sensitivity and noise floor.MEMS physical sensors, most commonly, rely on force coupling and a resulting deflection of a proof mass or membrane to produce an output proportional to a stimulus of the physical quantity to be measured. Therefore, the sensitivity to a physical quantity may be improved by increasing the resulting deflection of a sensor. The work presented in this thesis introduces an approach based on a mechanical motion amplifier with the potential to improve the performance of mechanical MEMS sensors that rely on deflection to produce an output signal.The mechanical amplifier is integrated with the suspension system of a sensor. It comprises a system of micromachined levers (microlevers) to enhance the deflection of a proof mass caused by an inertial force. The mechanism can be used in capacitive accelerometers and gyroscopes to improve their performance by increasing their output signal. As the noise contribution of the electronic read-out circuit of a MEMS sensor is, to first order, independent of the amplitude of its input signal, the overall signal-to-noise ratio (SNR) of the sensor is improved.There is a rather limited number of reports in the literature for mechanical amplification in MEMS devices, especially when applied to amplify the deflection of inertial sensors. In this study, after a literature review, mathematical and computational methods to analyse the behaviour of microlevers were considered. By using these methods the mechanical and geometrical characteristics of microlevers components were evaluated. In order to prove the concept, a system of microlevers was implemented as a mechanical amplifier in capacitive accelerometers.All the mechanical structures were simulated using Finite Element Analysis (FEA) and system level simulations. This led to first order optimised devices that were used to design appropriate masks for fabrication. Two main fabrication processes were used; a Silicon on Insulator (SOI) process and a Silicon on Glass (SoG) process. The SOI process carried out at the University of Southampton evolved from a one mask to a two mask dicing free process with a yield of over 95%, in its third generation. The SoG is a well-established process at the University of Peking that uses three masks.The sensors were evaluated using both optical and electrical means. The results from the first prototype sensor design (1HAN) revealed an amplification factor of 40 and a mechanically amplified sensitivity of 2.39V/g. The measured natural frequency of the first mode of the sensor was at 734Hz and the full-scale measurement range was up to 7g with a maximum nonlinearity of 2%. The measurements for all the prototype sensor designs were very close to the predicted values with the highest discrepancy being 22%. The results of this research show that mechanical amplification is a very promising concept that can offer increased sensitivity in inertial sensors without increasing the noise. Experimental results show that there is plenty of room for improvement and that viable solutions may be produced by using the presented approach. The applications of this scheme are not restricted only to inertial sensors but as the results show it can be used in a broader range of micromachined devices

Single-Chip Scanning Probe Microscopes

Scanning probe microscopes (SPMs) are the highest resolution imaging instruments available today and are among the most important tools in nanoscience. Conventional SPMs suffer from several drawbacks owing to their large and bulky construction and to the use of piezoelectric materials. Large scanners have low resonant frequencies that limit their achievable imaging bandwidth and render them susceptible to disturbance from ambient vibrations. Array approaches have been used to alleviate the bandwidth bottleneck; however as arrays are scaled upwards, the scanning speed must decline to accommodate larger payloads. In addition, the long mechanical path from the tip to the sample contributes thermal drift. Furthermore, intrinsic properties of piezoelectric materials result in creep and hysteresis, which contribute to image distortion. The tip-sample interaction signals are often measured with optical configurations that require large free-space paths, are cumbersome to align, and add to the high cost of state-of-the-art SPM systems. These shortcomings have stifled the widespread adoption of SPMs by the nanometrology community. Tiny, inexpensive, fast, stable and independent SPMs that do not incur bandwidth penalties upon array scaling would therefore be most welcome. The present research demonstrates, for the first time, that all of the mechanical and electrical components that are required for the SPM to capture an image can be scaled and integrated onto a single CMOS chip. Principles of microsystem design are applied to produce single-chip instruments that acquire images of underlying samples on their own, without the need for off-chip scanners or sensors. Furthermore, it is shown that the instruments enjoy a multitude of performance benefits that stem from CMOS-MEMS integration and volumetric scaling of scanners by a factor of 1 million. This dissertation details the design, fabrication and imaging results of the first single-chip contact-mode AFMs, with integrated piezoresistive strain sensing cantilevers and scanning in three degrees-of-freedom (DOFs). Static AFMs and quasi-static AFMs are both reported. This work also includes the development, fabrication and imaging results of the first single-chip dynamic AFMs, with integrated flexural resonant cantilevers and 3 DOF scanning. Single-chip Amplitude Modulation AFMs (AM-AFMs) and Frequency Modulation AFMs (FM-AFMs) are both shown to be capable of imaging samples without the need for any off-chip sensors or actuators. A method to increase the quality factor (Q-factor) of flexural resonators is introduced. The method relies on an internal energy pumping mechanism that is based on the interplay between electrical, mechanical, and thermal effects. To the best of the author’s knowledge, the devices that are designed to harness these effects possess the highest electromechanical Qs reported for flexural resonators operating in air; electrically measured Q is enhanced from ~50 to ~50,000 in one exemplary device. A physical explanation for the underlying mechanism is proposed. The design, fabrication, imaging, and tip-based lithographic patterning with the first single-chip Scanning Thermal Microscopes (SThMs) are also presented. In addition to 3 DOF scanning, these devices possess integrated, thermally isolated temperature sensors to detect heat transfer in the tip-sample region. Imaging is reported with thermocouple-based devices and patterning is reported with resistive heater/sensors. An “isothermal electrothermal scanner” is designed and fabricated, and a method to operate it is detailed. The mechanism, based on electrothermal actuation, maintains a constant temperature in a central location while positioning a payload over a range of >35μm, thereby suppressing the deleterious thermal crosstalk effects that have thus far plagued thermally actuated devices with integrated sensors. In the thesis, models are developed to guide the design of single-chip SPMs and to provide an interpretation of experimental results. The modelling efforts include lumped element model development for each component of single-chip SPMs in the electrical, thermal and mechanical domains. In addition, noise models are developed for various components of the instruments, including temperature-based position sensors, piezoresistive cantilevers, and digitally controlled positioning devices

Design and fabrication of precision carbon nanotube-based flexural transducers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 179-197).As mechanical devices move towards the nanoscale, smaller and more sensitive force and displacement sensors need to be developed. Currently, many biological, materials science, and nanomanufacturing applications could benefit from multi-axis micro- and nanoscale sensors with fine force and displacement resolutions. Unfortunately, such systems do not yet exist due to the limitations of traditional sensing techniques and fabrication procedures. Carbon nanotube-based (CNT) piezoresistive transducers offer the potential to overcome many of these limitations. Previous research has shown the potential for the use of CNTs in high resolution micro- and nanoscale sensing devices due to the high gauge factor and inherent size of CNTs. However, a better understanding of CNT-based piezoresistive sensors is needed in order to be able to design and engineer CNT-based sensor systems to take advantage of this potential. The purpose of this thesis is to take CNT-based strain sensors from the single element test structures that have been fabricated and turn them into precision sensor systems that can be used in micro- and nanoscale force and displacement transducers. In order to achieve this purpose and engineer high resolution CNT-based sensor systems, the design and manufacturing methods used to create CNT-based piezoresistive sensors were investigated. At the system level, a noise model was developed in order to be able to optimize the design of the sensor system. At the element level, a link was established between the structure of the CNT and its gauge factor using a theoretical model developed from quantum mechanics. This model was confirmed experimentally using CNT-based piezoresistive sensors integrated into a microfabricated test structure. At the device level, noise mitigation techniques including annealing and the use of a protective ceramic coating were investigated in order to reduce the noise in the sensor. From these investigations, best practices for the design and manufacturing of CNT-based piezoresistive sensors were established. Using these best practices, it is possible to increase the performance of CNT-based piezoresistive sensor systems by more than three orders of magnitude. These best practices were implemented in the design and fabrication of a multi-axis force sensor used to measure the adhesion force of an array of cells to the different material's surfaces for the development of biomedical implants. This force sensor is capable of measuring forces in the z-axis as well as torques in the [theta]x and [theta]y axis. The range and resolution of the force sensor were determined to be 84 [mu]N and 5.6 nN, respectively. This corresponds to a dynamic range of 83 dB, which closely matches the dynamic range predicted by the system noise model used to design the sensor. The accuracy of the force sensor is better than 1% over the device's full range.by Michael A. Cullinan.Ph.D

Six Degree of Freedom Force/Torque Sensor

The use of robots and manipulators in many kind of applications, such as scientific, medical or industrial ones, requires efficient multi-component force sensing schemes to control the force exerted by the robot end-effector on a human or an object. A multiaxis force sensor can be used to measure the contact force as accurately as possible, and to feed it back to the command signal so that the robot can achieve the pre-specified contact force. As the commercial force sensors are complex and expensive, the goal of this work is to make a multiaxis force sensor that could rThis work describes the design, development and calibration of a complete six?degree-of-freedom force and torque sensor. Compared to commercial sensors, this design has the advantage of simplicity and low cost. The sensor was machined from aluminium, and sensed by an array of commercial low-cost strain gauges. As a sensor, it could be applied in multi-DOF industrial, scientific and medical robotic systems, for instance