91 research outputs found
Design Optimization for an Electro-Thermally Actuated Polymeric Microgripper
Thermal micro-actuators are a promising solution to the need for
large-displacement, gentle handling force, low-power MEMS actuators. Potential
applications of these devices are micro-relays, assembling and miniature
medical instrumentation. In this paper the development of thermal
microactuators based on SU-8 polymer is described. The paper presents the
development of a new microgripper which can realize a movement of the gripping
arms with possibility for positioning and manipulating of the gripped object.
Two models of polymeric microgripper electrothermo- mechanical actuated, using
low actuation voltages, designed for SU-8 polymer fabrication were presented.
The electro-thermal microgrippers were designed and optimized using finite
element simulations. Electro-thermo-mechanical simulations based on finite
element method were performed for each of the model in order to compare the
results. Preliminary experimental tests were carried out.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
Hybrid Design of a Polymeric Electrothermal Actuator for Microgripper
Thermal micro actuators are widely used for large displacement, high accuracy and repeatability. The applications of these devices are in the fields of micro assembly, micro surgery and manipulation of micro particles. In this paper, the development of electro thermal micro actuator based on PMMA (Poly Meta Methyl Acrylate) is described. The paper presents the development of a new micro actuator for a microgripper which has a combination of asymmetric arm and bi-layer structure to completely eliminate the undesirable out of plane movement. Three models of electro thermally actuated polymeric micro actuators using low voltage of 0.1 V are designed and analyzed using COMSOL Multiphysics software. The results are discussed and compared to show the efficiency of the hybrid design. The hybrid design gives 2.5 μm of in plane gripping displacement and 0.02 μm out of plane displacement at 0.1 V
Dynamic modelling for thermal micro-actuators using thermal networks.
International audienceThermal actuators are extensively used in microelectromechanical systems (MEMS). Heat transfer through and around these microstructures are very complex. Knowing and controlling them in order to improve the performance of the micro-actuator, is currently a great challenge. This paper deals with this topic and proposes a dynamic thermal modelling of thermal micro-actuators. Thermal problems may be modelled using electrical analogy. However, current equivalent electrical models (thermal networks) are generally obtained considering only heat transfers through the thickness of structures having considerable height and length in relation to width (walls). These models cannot be directly applied to micro-actuators. In fact, microactuator congurations are based on 3D beam structures, and heat transfers occur through and around length. New dynamic and static thermal networks are then proposed in this paper. The validities of both types of thermal networks have been studied. They are successfully validated by comparison with nite elements simulation and analytical calculations
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
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
Simulation and optimization of a silicon-polymer bimorph microgripper
This paper presents an electro-thermally bimorph microgripper based on silicon-polymer laterally stacked structures and a method to optimized the fabricated device. The actuated displacement is enhanced due to the polymer constraint effect. Both the thermal expansion and apparent Young’s modulus of the constrained polymer blocks are significantly improved, compared with the no constraint one. The device consists of a serpentine-shape deep silicon structure with a thin film aluminum heater on the top and filling polymer in the trenches among the vertical silicon parts. The fabricated bimorph microgripper can operate in four modes and generates a large motion up to 15 μm. The simulated results are met the fabricated measurements. An optimized structure is proposed for decreasing the working temperature, power consumption but increasing the output displacement. The simulated results are showed that the output displacement is increased up to 550% and temperature profile improved considerably. This electro-thermally silicon-polymer opened and closed microgripper can be used in micro-robotics, micro-assembly, minimally invasive surgery, living cells surgery.
Waveguide microgripper for identification, sensing and manipulation
A Waveguide Microgripper utilizes flexible optical waveguides as gripping arms, which provide the physical means for grasping a microobject, while simultaneously enabling light to be delivered and collected. This unique capability allows extensive optical characterization of the structure being held such as transmission, reflection or fluorescence. One of the simplest capabilities of the waveguide microgripper is to be able to detect the presence of a microobject between the microgripper facets by monitoring the transmitted intensity of light coupled through the facets. The intensity of coupled light is expected to drop when there is an object obstructing the path of light. The optical sensing and characterization function of the microgripper is a strong function of the optical power incident on the structure of interest. Hence it is important to understand the factors affecting the power distribution across the facet. The microgripper is also capable of detecting the fluorescence. This capability of microgripper is expected to have applications in medical, bio-medical and related fields
Lateral bending liquid crystal elastomer beams for microactuators and microgrippers
With the rapid development of microsystems in the last few decades, there is a
requirement for high precision tools for micromanipulation and transportation of micro-objects, such as microgrippers, for applications in microassembly, microrobotics, life
sciences and biomedicine. Polymer based microgrippers and microrobots executing
various tasks have been of significant interest as an alternative to the traditional silicon
and metal based counterparts due to the advantages of low cost fabrication, low
actuation temperature, biocompatibility, and sensitivity to various stimuli. The
exceptional actuation properties of liquid crystal elastomers (LCE) have made these
materials highly attractive for various emerging applications in the last two decades.
Large programmable deformations and the benefits offered by the elastic, thermal and
optical properties of LCEs are suitable for implementing stimuli-responsive
microgrippers as well as various biomimetic motion in soft robots.
In this thesis, a method and the associated processes for fabrication and molecular
alignment in LCE were developed, which enabled new functionality and improved
performance of the LCE based microactuators and microgrippers, providing controlled
response by thermal and remote photothermal actuation, and allowing easy integration
of the LCE end-effectors into robotic systems for automated operation. Lateral bending
actuation has been demonstrated in LCE microbeams of 900 µm of length and 40 µm of
thickness, owing to the new monolithic micromolding technique using vertical patterned
walls for alignment. The effects of parameters such as the beam width, the size of the
microgrooves, and the surface treatment method on the behavior of the microactuators
were studied; the internal alignment pattern of liquid crystals in the structure was
investigated by different microscopy methods. An efficient method for finite element
modeling of the bending LCE actuators was developed and experimentally verified,
based on the gradient of equivalent thermal expansion in the multi-layer structure,
which was able to predict the bending behavior of the actuators in a large range of
thicknesses as well as rolling behavior of the actuators of tapered thickness. The novel
LCE microgripper with in-plane operation showed efficient thermal and photothermal
actuation, achieving the gripping stroke of 64 µm under the light intensity of 239
mW/cm2
for the gripper length of 900 µm, which is more efficient than the typical SU-8
polymer based microgrippers of the same dimensions. The LCE gripper was
successfully demonstrated for the application in manipulation of the objects of tens to
hundreds of micrometers in size. Therefore, the novel LCE microgripper bridges the gap in the LCE-based gripper technologies for typical object size in applications for
systems microassembly, biological and cell micromanipulation. The lateral bending
functionality enabled by the proposed method expands design opportunities for thermal
and photothermal LCE microactuators, providing an effective route toward realization
of new modes of gripping, locomotion, and cargo transportation in soft microrobotics
and micromanipulation
A 3D-printed polymer micro-gripper with self-defined electrical tracks and thermal actuator
This paper presents a simple fabrication process that allows for isolated metal tracks to be easily defined on the surface of 3D printed micro-scale polymer components. The process makes use of a standard low cost conformal sputter coating system to quickly deposit thin film metal layers on to the surface of 3D printed polymer micro parts. The key novelty lies in the inclusion of inbuilt masking features, on the surface of the polymer parts, to ensure that the conformal metal layer can be effectively broken to create electrically isolated metal features. The presented process is extremely flexible, and it is envisage that it may be applied to a wide range of sensor and actuator applications. To demonstrate the process a polymer micro-scale gripper with an inbuilt thermal actuator is designed and fabricated. In this work the design methodology for creating the micro-gripper is presented, illustrating how the rapid and flexible manufacturing process allows for fast cycle time design iterations to be performed. In addition the compatibility of this approach with traditional design and analysis techniques such as basic finite element simulation is also demonstrated with simulation results in reasonable agreement with experimental performance data for the micro-gripper
- …