Development of novel micropneumatic grippers for biomanipulation

Microbjects with dimensions from 1 μm to 1 mm have been developed recently for different aspects and purposes. Consequently, the development of handling and manipulation tools to fulfil this need is urgently required. Micromanipulation techniques could be generally categorized according to their actuation method such as electrostatic, thermal, shape memory alloy, piezoelectric, magnetic, and fluidic actuation. Each of which has its advantage and disadvantage. The fluidic actuation has been overlooked in MEMS despite its satisfactory output in the micro-scale. This thesis presents different families of pneumatically driven, low cost, compatible with biological environment, scalable, and controllable microgrippers. The first family demonstrated a polymeric microgripper that was laser cut and actuated pneumatically. It was tested to manipulate microparticles down to 200 microns. To overcome the assembly challenges that arise in this family, the second family was proposed. The second family was a micro-cantilever based microgripper, where the device was assembled layer by layer to form a 3D structure. The microcantilevers were fabricated using photo-etching technique, and demonstrated the applicability to manipulate micro-particles down to 200 microns using automated pick-and-place procedure. In addition, this family was used as a tactile-detector as well. Due to the angular gripping scheme followed by the above mentioned families, gripping smaller objects becomes a challenging task. A third family following a parallel gripping scheme was proposed allowing the gripping of smaller objects to be visible. It comprises a compliant structure microgripper actuated pneumatically and fabricated using picosecond laser technology, and demonstrated the capability of gripping microobject as small as 100 μm microbeads. An FEA modelling was employed to validate the experimental and analytical results, and excellent matching was achieved

The effects of cold arm width and metal deposition on the performance of a U-Beam electrothermal MEMS microgripper for biomedical applications

Microelectromechanical systems (MEMS) have established themselves within various fields dominated by high-precision micromanipulation, with the most distinguished sectors being the microassembly, micromanufacturing and biomedical ones. This paper presents a horizontal electrothermally actuated 'hot and cold arm' microgripper design to be used for the deformability study of human red blood cells (RBCs). In this study, the width and layer composition of the cold arm are varied to investigate the effects of dimensional and material variation of the cold arm on the resulting temperature distribution, and ultimately on the achieved lateral displacement at the microgripper arm tips. The cold arm widths investigated are 14 μm, 30 μm, 55 μm, 70 μm and 100 μm. A gold layer with a thin chromium adhesion promoter layer is deposited on the top surface of each of these cold arms to study its effect on the performance of the microgripper. The resultant ten microgripper design variants are fabricated using a commercially available MEMS fabrication technology known as a silicon-on-insulator multi-user MEMS process (SOIMUMPs)TM. This process results in an overhanging 25 μm thick single crystal silicon microgripper structure having a low aspect ratio (width:thickness) value compared to surface micromachined structures where structural thicknesses are of the order of 2 μm. Finite element analysis was used to numerically model the microgripper structures and coupled electrothermomechanical simulations were implemented in CoventorWare ®. The numerical simulations took into account the temperature dependency of the coefficient of thermal expansion, the thermal conductivity and the electrical conductivity properties in order to achieve more reliable results. The fabricated microgrippers were actuated under atmospheric pressure and the experimental results achieved through optical microscopy studies conformed with those predicted by the numerical models. The gap opening and the temperature rise at the cell gripping zone were also compared for the different microgripper structures in this work, with the aim of identifying an optimal microgripper design for the deformability characterisation of RBCs.peer-reviewe

A microgripper for single cell manipulation

This thesis presents the development of an electrothermally actuated microgripper for the manipulation of cells and other biological particles. The microgripper has been fabricated using a combination of surface and bulk micromachining techniques in a three mask process. All of the fabrication details have been chosen to enable a tri-layer, polymer (SU8) - metal (Au) - polymer (SU8), membrane to be released from the substrate stress free and without the need for sacrificial layers. An actuator design, which completely eliminates the parasitic resistance of the cold arm, is presented. When compared to standard U-shaped actuators, it improves the thermal efficiency threefold. This enables larger displacements at lower voltages and temperatures. The microgripper is demonstrated in three different configurations: normally open mode, normally closed mode, and normally open/closed mode. It has-been modelled using two coupled analytical models - electrothermal and thermomechanical - which have been custom developed for this application. Unlike previously reported models, the electrothermal model presented here includes the heat exchange between hot and cold arms of the actuators that are separated by a small air gap. A detailed electrothermomechanical characterisation of selected devices has permitted the validation of the models (also performed using finite element analysis) and the assessment of device performance. The device testing includes electrical, deflection, and temperature measurements using infrared (IR) thermography, its use in polymeric actuators reported here for the first time. Successful manipulation experiments have been conducted in both air and liquid environments. Manipulation of live cells (mice oocytes) in a standard biomanipulation station has validated the microgripper as a complementary and unique tool for the single cell experiments that are to be conducted by future generations of biologists in the areas of human reproduction and stem cell research

Force Sensing and Control in Micromanipulation

Ph.DDOCTOR OF PHILOSOPH

Design of a Piezoelectric-actuated microgripper with a three-stage flexure-based amplification

This paper presents a novel microgripper mechanism for micromanipulation and assembly. The microgripper is driven by a piezoelectric actuator, and a three-stage flexure-based amplification has been designed to achieve large jaw displacements. The kinematic, static and dynamic models of the microgripper have been established and optimized considering the crucial parameters that determine the characteristics of the microgripper. Finite element analysis was conducted to evaluate the characteristics of the microgripper, and wire electro discharge machining technique was utilized to fabricate the monolithic structure of the microgripper mechanism. Experimental tests were carried out to investigate the performance of the microgripper and the results show that the microgripper can grasp microobjects with the maximum jaw motion stroke of 190 μm corresponding to the 100-V applied voltage. It has an amplification ratio of 22.8 and working mode frequency of 953 Hz

Microgripper design and evaluation for automated µ-wire assembly: a survey

Microgrippers are commonly used for micromanipulation of micro-objects from 1 to 100 µm and attain features of reliable accuracy, low cost, wide jaw aperture and variable applied force. This paper aim is to review the design of different microgrippers which can manipulate and assemble µ-wire to PCB connectors. A review was conducted on microgrippers’ technologies, comparing fundamental components of structure and actuators’ types, which determined the most suitable design for the required micromanipulation task. Various microgrippers’ design was explored to examine the suitability and the execution of requirements needed for successful micromanipulation

Workshop on "Robotic assembly of 3D MEMS".

Proceedings of a workshop proposed in IEEE IROS'2007.The increase of MEMS' functionalities often requires the integration of various technologies used for mechanical, optical and electronic subsystems in order to achieve a unique system. These different technologies have usually process incompatibilities and the whole microsystem can not be obtained monolithically and then requires microassembly steps. Microassembly of MEMS based on micrometric components is one of the most promising approaches to achieve high-performance MEMS. Moreover, microassembly also permits to develop suitable MEMS packaging as well as 3D components although microfabrication technologies are usually able to create 2D and "2.5D" components. The study of microassembly methods is consequently a high stake for MEMS technologies growth. Two approaches are currently developped for microassembly: self-assembly and robotic microassembly. In the first one, the assembly is highly parallel but the efficiency and the flexibility still stay low. The robotic approach has the potential to reach precise and reliable assembly with high flexibility. The proposed workshop focuses on this second approach and will take a bearing of the corresponding microrobotic issues. Beyond the microfabrication technologies, performing MEMS microassembly requires, micromanipulation strategies, microworld dynamics and attachment technologies. The design and the fabrication of the microrobot end-effectors as well as the assembled micro-parts require the use of microfabrication technologies. Moreover new micromanipulation strategies are necessary to handle and position micro-parts with sufficiently high accuracy during assembly. The dynamic behaviour of micrometric objects has also to be studied and controlled. Finally, after positioning the micro-part, attachment technologies are necessary

Workshop on "Control issues in the micro / nano - world".

International audienceDuring the last decade, the need of systems with micro/nanometers accuracy and fast dynamics has been growing rapidly. Such systems occur in applications including 1) micromanipulation of biological cells, 2) micrassembly of MEMS/MOEMS, 3) micro/nanosensors for environmental monitoring, 4) nanometer resolution imaging and metrology (AFM and SEM). The scale and requirement of such systems present a number of challenges to the control system design that will be addressed in this workshop. Working in the micro/nano-world involves displacements from nanometers to tens of microns. Because of this precision requirement, environmental conditions such as temperature, humidity, vibration, could generate noise and disturbance that are in the same range as the displacements of interest. The so-called smart materials, e.g., piezoceramics, magnetostrictive, shape memory, electroactive polymer, have been used for actuation or sensing in the micro/nano-world. They allow high resolution positioning as compared to hinges based systems. However, these materials exhibit hysteresis nonlinearity, and in the case of piezoelectric materials, drifts (called creep) in response to constant inputs In the case of oscillating micro/nano-structures (cantilever, tube), these nonlinearities and vibrations strongly decrease their performances. Many MEMS and NEMS applications involve gripping, feeding, or sorting, operations, where sensor feedback is necessary for their execution. Sensors that are readily available, e.g., interferometer, triangulation laser, and machine vision, are bulky and expensive. Sensors that are compact in size and convenient for packaging, e.g., strain gage, piezoceramic charge sensor, etc., have limited performance or robustness. To account for these difficulties, new control oriented techniques are emerging, such as[d the combination of two or more ‘packageable' sensors , the use of feedforward control technique which does not require sensors, and the use of robust controllers which account the sensor characteristics. The aim of this workshop is to provide a forum for specialists to present and overview the different approaches of control system design for the micro/nano-world and to initiate collaborations and joint projects

Principle, Design and Future of Inchworm Type Piezoelectric Actuators

The inchworm type piezoelectric actuator is one novel actuator to ensure a large working stroke with high resolution which has attracted the continuous attentions from researchers all over the world. In this study, the motion principle of the inchworm type piezoelectric is discussed: the “walker” pattern, the “pusher” pattern and hybrid “walker-pusher” pattern. The classification (linear, rotary and multi-DOF) and development are introduced in details, some significant researches are illustrated. Finally, the future direction of inchworm type piezoelectric actuators is pointed out according the development of inchworm type piezoelectric actuators. This study shows the clear principle, design and future of inchworm type piezoelectric actuators which is meaningful for the development of piezoelectric actuators

Performance of Smart Materials-Based Instrumentation for Force Measurements in Biomedical Applications: A Methodological Review

The introduction of smart materials will become increasingly relevant as biomedical technologies progress. Smart materials sense and respond to external stimuli (e.g., chemical, electrical, mechanical, or magnetic signals) or environmental circumstances (e.g., temperature, illuminance, acidity, or humidity), and provide versatile platforms for studying various biological processes because of the numerous analogies between smart materials and biological systems. Several applications based on this class of materials are being developed using different sensing principles and fabrication technologies. In the biomedical field, force sensors are used to characterize tissues and cells, as feedback to develop smart surgical instruments in order to carry out minimally invasive surgery. In this regard, the present work provides an overview of the recent scientific literature regarding the developments in force measurement methods for biomedical applications involving smart materials. In particular, performance evaluation of the main methods proposed in the literature is reviewed on the basis of their results and applications, focusing on their metrological characteristics, such as measuring range, linearity, and measurement accuracy. Classification of smart materials-based force measurement methods is proposed according to their potential applications, highlighting advantages and disadvantages