Electrostatic micro actuators for mirror and other applications

Micro-electro-mechanical systems (MEMS) based electrostatic micro actuators are becoming important building blocks for innovations in optical signal processing and computing systems due to their inherently small size, high density, high speed and low power consumption. Generally, the principle of operation in these systems can be described as: an electrostatic attractive force causes a mechanical rotation, translation or deformation of a mirror plate, controlling the power, phase or direction of a light beam while it propagates through some medium or through free space. The fast paced, competitive research and development efforts widely being undertaken, both in academia and industry, are demanding simple, fast methods for the design of quasi-static Mirror systems, with a large, stable, analog range of operation. In addition fast prototyping methods are in demand for the proof of concept fabrication of these mirror designs. This dissertation addresses these research topics by presenting 1) a general capacitance-based quasi-static design theory and methodology for electrostatic micro actuators, 2) a study of electrostatic travel range extension methods to minimize the pull in effect, and 3) a fast prototyping approach for electrostatic mirror devices using ultra thin silicon wafer bonding and deep reactive etching technologies. In the first topic, two fundamental capacitance-based differential equations are developed for the quasi-static description of electrostatic micro actuator systems. A structural equation is developed to represent the coupled electromechanical response of the system under applied voltage bias, and a pull in equation is determined to identify the intrinsic collapse point beyond which an actuator system no longer has a stable equilibrium, the so-called pull in point. These equations are applied to various complex electrostatic micro actuator systems to predict specific quasi-static behavior. A unitless equation is introduced for each actuator category, and based on it, a design method is proposed to quickly provide specifications for a particular desired performance of an electrostatically actuated micro-mirror system. In the second topic, and as an application of the proposed design methodology, the travel range extension issue is addressed leading to two new methods to increase travel range by sacrificing driving voltage. Both methods are applied directly in the electrostatic domain. The first method utilizes a series capacitor to modulate the effective actuation voltage across the variable capacitor micro mirror. The second method utilizes negative feedback due to the coulombic repulsive interaction between charge layers inserted between the micro mirror electrodes. An analytical study of representative mirror devices is presented, and verification of the travel range extension models is provided via finite element analysis (FEA) simulation. As a further application of the design methodology developed as part of the first research topic, three state-of-the-art micro actuator systems are designed and studied: 1) a variable optical attenuator (VOA), 2) an optical cross connect device (OXC) and 3) an electrostatically tunable, wavelength selecting device. FEA simulations are used to confirm design specifications. In the third research topic, VOA and electrostatically tunable, wavelength selecting devices are fabricated using fast prototyping via ultra thin wafer bonding and deep reactive etching (DRIIE) technologies. Both silicon wet-etching and SU-8 patterning are investigated for the formation of mirror gaps. Testing in the mechanical domain and partial device characterization in the optical domain is provided for these devices. Finally, as a demonstration that the actuator design approach developed in this thesis can be applied to systems other than micro mirrors, we use the approach to design an innovative true mass flow sensor using an electrostatic resonant beam as the sensing element

Causes and 3-year-incidence of blindness in Jing-An District, Shanghai, China 2001-2009

<p>Abstract</p> <p>Background</p> <p>Registered data can provide valuable information regarding blindness. The purpose of this study was to evaluate the main causes and 3-year incidence of registered blindness in Jing-An district in Shanghai, China.</p> <p>Methods</p> <p>Data from the blindness registry (age, gender and cause of visual disability) were collected and analyzed. The prevalence of blindness for 2003, 2007, 2009 and the 3-year incidence of blindness were calculated.</p> <p>Results</p> <p>The reported blindness increased significantly from 113.7 per 100,000 in 2003 to 145.8 per 100,000 in 2006 to 165.9 per 100,000 in 2009 (P < 0.05, P < 0.05, respectively). Age significantly affects prevalence; the odd ratios (OR) were 2.57 in the 30 y - 49 y range (P < 0.001), 7.27 in the 50 y - 69 y range (P < 0.001) and 21.2 in the ≥ 70 y (P < 0.001). The 3-year incidence increased from 32.3 per 100,000 in 2001-2003 to 34.2 per 100,000 in 2004-2006 to 40.8 per 100,000 in 2007-2009. The causes of new blindness registered in 2001-2009 were myopic macular degeneration (19.4%), followed by glaucoma (17.7%), age-related macular degeneration (11.8%), optical nerve atrophy (9.4%), retinitis pigmentosa (8.6%), diabetic retinopathy (7.8%) and corneal opacity (5.8%).</p> <p>Conclusions</p> <p>The 3-year incidence and prevalence of registered blindness increased in the past 9 years. The leading causes of new blindness were myopic macular degeneration, glaucoma and age-related macular degeneration. The pattern of causes has changed little in the past 9 years and is different from other locations in China. The pattern is similar to that of Taiwan, Hongkong, and Western countries.</p

Polarization control proposal for Shanghai deep ultraviolet free electron laser

In this paper, a fully coherent radiation option with controllable polarization is proposed for Shanghai deep ultraviolet free electron laser (FEL) test facility. Intensive start-to-end simulation suggests that, the two crossed planar undulators which generate the horizontal and vertical linear polarized FEL respectively, should be placed as close as possible for avoiding the polarization performance degradation of the final combined FEL radiation. With the existence of the phase-shifter between the two crossed radiators, Fourier-Transform-Limited output radiation with 100 nJ order pulse energy, 5 ps full pulse length and circular polarization degree above 90% could be achieved.Comment: 9 pages, 5 figures, 1 tabl

DNA-Interacting Characteristics of the Archaeal Rudiviral Protein SIRV2_Gp1

Whereas the infection cycles of many bacterial and eukaryotic viruses have been characterized in detail, those of archaeal viruses remain largely unexplored. Recently, studies on a few model archaeal viruses such as SIRV2 (Sulfolobus islandicus rod-shaped virus) have revealed an unusual lysis mechanism that involves the formation of pyramidal egress structures on the host cell surface. To expand understanding of the infection cycle of SIRV2, we aimed to functionally characterize gp1, which is a SIRV2 gene with unknown function. The SIRV2_Gp1 protein is highly expressed during early stages of infection and it is the only protein that is encoded twice on the viral genome. It harbours a helix-turn-helix motif and was therefore hypothesized to bind DNA. The DNA-binding behavior of SIRV2_Gp1 was characterized with electrophoretic mobility shift assays and atomic force microscopy. We provide evidence that the protein interacts with DNA and that it forms large aggregates, thereby causing extreme condensation of the DNA. Furthermore, the N-terminal domain of the protein mediates toxicity to the viral host Sulfolobus. Our findings may lead to biotechnological applications, such as the development of a toxic peptide for the containment of pathogenic bacteria, and add to our understanding of the Rudiviral infection cycle.status: publishe