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

Micro-fabrication of bio-MEMS based force sensor to measure the force response of living cells

Understanding how a living cell behaves has become a very important topic in today’s research field. Hence, different sensors and testing devices have been designed to test the mechanical properties of these living cells. This thesis presents a method of micro-fabricating a bio-MEMS based force sensor which is used to measure the force response of living cells. Initially, the basic concepts of MEMS have been discussed and the different micro-fabrication techniques used to manufacture various MEMS devices have been described. There have been many MEMS based devices manufactured and employed for testing many nano-materials and bio-materials. Each of the MEMS based devices described in this thesis use a novel concept of testing the specimens. The different specimens tested are nano-tubes, nano-wires, thin film membranes and biological living cells. Hence, these different devices used for material testing and cell mechanics have been explained. The micro-fabrication techniques used to fabricate this force sensor has been described and the experiments preformed to successfully characterize each step in the fabrication have been explained. The fabrication of this force sensor is based on the facilities available at Michigan Technological University. There are some interesting and uncommon concepts in MEMS which have been observed during this fabrication. These concepts in MEMS which have been observed are shown in multiple SEM images

Characterization of the mechanical properties of freestanding platinum thin films

Many MEMS devices utilize nanocrystalline thin metallic films as mechanical structures, in particular, micro switching devices where these films are used as Ohmic contacts. But the elastic and plastic properties of these thin films (thickness \u3c 1μm) are significantly different from those of the bulk material. At these scales the volume fraction of material defects such as: grain boundaries, dislocations and interstitials become quite significant and become a chief contributor to the physical and mechanical material properties. In order to effectively design MEMS devices it is important that these material properties are explored and mechanical behavior of the structure they form be characterized. Popular thin film materials used in MEMS devices are Aluminum (Al), Copper (Cu), Nickel (Ni) and Gold (Au). Platinum has traditionally gained acceptance into the MEMS industry because of its chemical inertness and high temperature stability. However the mechanical properties of platinum remains the least exploited. Platinum has a high Youngs Modulus (164 GPa, for bulk) and high melting temperature (1768 oC) and therefore can be used as a \u27thin film\u27 structure (cantilever, a bridge or a membrane) in high temperature environments with high resistance to mechanical failure. The physical size of these thin film structure make it very difficult to handle them and employ traditional mechanical testing methodologies and techniques and therefore require custom test platforms. One such recently developed platform is presented in this dissertation. The test platform is comprised of a microfabricated cascaded thermal actuator system and test specimen. The cascaded thermal actuator system is capable of providing tens of microns of displacement and tens of milli-Newton forces simultaneously while applying a relatively low temperature gradient across the test specimen. The dimensions of the platform make its use possible in both the SEM/TEM environments and on a probe station under an optical microscope. Digital image correlation was used to obtain similar accuracy (~10 nm) for displacement measurements in both an SEM and under an optical microscope. The mechanical behavior of nanocrystalline thin film structure has been the subject of extensive research in recent years. Mainly, the focus has been on the effects of the film thickness with only a few researchers mentioning anything about the grain sizes of their polycrystalline films. The effect of thin film cross sectional morphology on the mechanical behavior of a thin film structure has never been studied directly. Presented in this dissertation is experimental evidence that these thin film structures are composite structures of various grain morphologies and the overall mechanical behavior exhibited by them is the combined effect of individual contributions of each of these grain morphologies.\u2

MEMS Actuation and Self-Assembly Applied to RF and Optical Devices

The focus of this work involves optical and RF (radio frequency) applications of novel microactuation and self-assembly techniques in MEMS (Microelectromechanical systems). The scaling of physical forces into the micro domain is favorably used to design several types of actuators that can provide large forces and large static displacements at low operation voltages. A self-assembly method based on thermally induced localized plastic deformation of microstructures has been developed to obtain truly three-dimensional structures from a planar fabrication process. RF applications include variable discrete components such as capacitors and inductors as well as tunable coupling circuits. Optical applications include scanning micromirrors with large scan angles (>90 degrees), low operation voltages (<10 Volts), and multiple degrees of freedom. One and two-dimensional periodic structures with variable periods and orientations (with respect to an incident wave) are investigated as well, and analyzed using optical phased array concepts. Throughout the research, permanent tuning via plastic deformation and power-off latching techniques are used in order to demonstrate that the optical and RF devices can exhibit zero quiescent power consumption once their geometry is set

SOI RF-MEMS Based Variable Attenuator for Millimeter-Wave Applications

The most-attractive feature of microelectromechanical systems (MEMS) technology is that it enables the integration of a whole system on a single chip, leading to positive effects on the performance, reliability and cost. MEMS has made it possible to design IC-compatible radio frequency (RF) devices for wireless and satellite communication systems. Recently, with the advent of 5G, there is a huge market pull towards millimeter-wave devices. Variable attenuators are widely employed for adjusting signal levels in high frequency equipment. RF circuits such as automatic gain control amplifiers, broadband vector modulators, full duplex wireless systems, and radar systems are some of the primary applications of variable attenuators. This thesis describes the development of a millimeter-wave RF MEMS-based variable attenuator implemented by monolithically integrating Coplanar Waveguide (CPW) based hybrid couplers with lateral MEMS varactors on a Silicon–on–Insulator (SOI) substrate. The MEMS varactor features a Chevron type electrothermal actuator that controls the lateral movement of a thick plate, allowing precise change in the capacitive loading on a CPW line leading to a change in isolation between input and output. Electrothermal actuators have been employed in the design instead of electrostatic ones because they can generate relatively larger in-line deflection and force within a small footprint. They also provide the advantage of easy integration with other electrical micro-systems on the same chip, since their fabrication process is compatible with general IC fabrication processes. The development of an efficient and reliable actuator has played an important role in the performance of the proposed design of MEMS variable attenuator. A Thermoreflectance (TR) imaging system is used to acquire the surface temperature profiles of the electrothermal actuator employed in the design, so as to study the temperature distribution, displacement and failure analysis of the Chevron actuator. The 60 GHz variable attenuator was developed using a custom fabrication process on an SOI substrate with a device footprint of 3.8 mm x 3.1 mm. The fabrication process has a high yield due to the high-aspect-ratio single-crystal-silicon structures, which are free from warping, pre-deformation and sticking during the wet etching process. The SOI wafer used has a high resistivity (HR) silicon (Si) handle layer that provides an excellent substrate material for RF communication devices at microwave and millimeter wave frequencies. This low-cost fabrication process provides the flexibility to extend this module and implement more complex RF signal conditioning functions. It is thus an appealing candidate for realizing a wide range of reconfigurable RF devices. The measured RF performance of the 60 GHz variable attenuator shows that the device exhibits attenuation levels (|S21|) ranging from 10 dB to 25 dB over a bandwidth of 4 GHz and a return loss of better than 20 dB. The thesis also presents the design and implementation of a MEMS-based impedance tuner on a Silicon-On-Insulator (SOI) substrate. The tuner is comprised of four varactors monolithically integrated with CPW lines. Chevron actuators control the lateral motion of capacitive thick plates used as contactless lateral MEMS varactors, achieving a capacitance range of 0.19 pF to 0.8 pF. The improvement of the Smith chart coverage is achieved by proper choice of the electrical lengths of the CPW lines and precise control of the lateral motion of the capacitive plates. The measured results demonstrate good impedance matching coverage, with an insertion loss of 2.9 dB. The devices presented in this thesis provide repeatable and reliable operation due to their robust, thick-silicon structures. Therefore, they exhibit relatively low residual stress and are free from stiction and micro-welding problems

Microrobots for wafer scale microfactory: design fabrication integration and control.

Future assembly technologies will involve higher automation levels, in order to satisfy increased micro scale or nano scale precision requirements. Traditionally, assembly using a top-down robotic approach has been well-studied and applied to micro-electronics and MEMS industries, but less so in nanotechnology. With the bloom of nanotechnology ever since the 1990s, newly designed products with new materials, coatings and nanoparticles are gradually entering everyone’s life, while the industry has grown into a billion-dollar volume worldwide. Traditionally, nanotechnology products are assembled using bottom-up methods, such as self-assembly, rather than with top-down robotic assembly. This is due to considerations of volume handling of large quantities of components, and the high cost associated to top-down manipulation with the required precision. However, the bottom-up manufacturing methods have certain limitations, such as components need to have pre-define shapes and surface coatings, and the number of assembly components is limited to very few. For example, in the case of self-assembly of nano-cubes with origami design, post-assembly manipulation of cubes in large quantities and cost-efficiency is still challenging. In this thesis, we envision a new paradigm for nano scale assembly, realized with the help of a wafer-scale microfactory containing large numbers of MEMS microrobots. These robots will work together to enhance the throughput of the factory, while their cost will be reduced when compared to conventional nano positioners. To fulfill the microfactory vision, numerous challenges related to design, power, control and nanoscale task completion by these microrobots must be overcome. In this work, we study three types of microrobots for the microfactory: a world’s first laser-driven micrometer-size locomotor called ChevBot，a stationary millimeter-size robotic arm, called Solid Articulated Four Axes Microrobot (sAFAM), and a light-powered centimeter-size crawler microrobot called SolarPede. The ChevBot can perform autonomous navigation and positioning on a dry surface with the guidance of a laser beam. The sAFAM has been designed to perform nano positioning in four degrees of freedom, and nanoscale tasks such as indentation, and manipulation. And the SolarPede serves as a mobile workspace or transporter in the microfactory environment

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

Optical packaging of microlens over UV-LED array

Abstract unavailable please refer to PD

Selectively Tuning a Buckled Si/SiO\u3csub\u3e2\u3c/sub\u3e Membrane MEMS through Joule Heating Actuation and Mechanical Restriction

This research followed previous work and attempted to modify the spring in two ways. First, a Ti/Au meander resistor was deposited atop the membrane in an effort to actuate the membrane and change the spring constant. Secondly, a series of overhanging cantilevers were attached to the bulk substrate surrounding the membrane in an effort to constrain the membrane buckling deflection to the negative stiffness region. Membrane buckling was investigated through Finite Element analysis (FEA) and analytical equations. Deflections were measured using an interferometric microscope (IFM) and force/deflection measurements were captured using a unique measurement scheme. The results concluded that by introducing a thermal stress, the membrane could be actuated with a corresponding 3x increase in spring constant. Additionally, the overhanging beams restricted the membrane deflection by up to 30%, but, because of a lack in beam stiffness, failed to restrict the membrane to the negative stiffness region. This research laid the ground work for future work in this area