Improved Autoadhesion Measurement Method for Micromachined Polysilicon Beams

1996 ◽  
Vol 444 ◽  
Author(s):  
Maarten P. de Boer ◽  
Terry A. Michalske
Keyword(s):  
Surface Chemistry ◽  
Optical Microscopy ◽  
Measurement Method ◽  
Current Practice ◽  
Cantilever Beams ◽  
Beam Length ◽  
Substrate Adhesion

AbstractWe have measured autoadhesion (e.g. stiction) of individual polysilicon beams by interferometric optical microscopy. Untreated cantilever beams were dried from water in air, while treated beams were coated with a hydrophobic molecular coating of octadecyltrichlorosilane (ODTS). Adhesion values obtained for beams adhered to the substrate over a long length (large d) are independent of beam length with values of 16.7 and 4.4 mJ/m2 for untreated and treated samples respectively. These values can be understood in terms of differences in surface chemistry and polysilicon roughness. Using the shortest length beam which remains attached to the substrate, adhesion values were 280 and 16 mJ/m2 respectively. These higher values may be a result of capillarity effects. We recommend that measurements be made on beams in which d is large, in contrast to the current practice of noting the shortest beam adhered.

Aging of the Gasket Materials in Simulated PEM Environment and Accelerated Mediums

2012 ◽  
Vol 509 ◽  
pp. 1-9
Author(s):  
Guo Li ◽  
Jin Zhu Tan ◽  
Jian Ming Gong
Keyword(s):  
Weight Loss ◽  
High Temperature ◽  
Fuel Cell ◽  
Surface Chemistry ◽  
Optical Microscopy ◽  
Pem Fuel Cell ◽  
Proton Exchange ◽  
Attenuated Total Reflection ◽  
Durability Test ◽  
Over Time

Silicon rubber is a potential material for gaskets in proton exchange membrane (PEM) fuel cell. So its long term stability and durability is crucial to the electrochemical performance of fuel cell especially in an acidic, high temperature, humid environment. In present paper, the aging process of silicon rubbers has been studied in one simulated PEM fuel cell medium and two accelerated durability test (ADT) mediums for short time test at 70oC and 90oC, respectively. Effect of exposure time, temperature and exposure medium on aging of silicone rubber is also compared. Weight loss is measured by electronic balance; topographical changes on samples’ surfaces are monitored by optical microscopy; Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of samples before and after exposure over time. The results show that the weight loss increased over time. Surface conditions of samples change over time from initially smooth to rough, crack appearance and finally crack propagation through Optical microscopy. ATR-FTIR results show that the surface chemistry changed significantly via de-crosslinking and chain scission in the backbone for materials over time. The aging degree is severe at high temperature or in high concentration acidic solution over time.

Chemical Degradation of the Silicone Rubber in Simulated PEMFC Environments

2011 ◽  
Vol 197-198 ◽  
pp. 741-748
Author(s):  
Guo Li ◽  
Jin Zhu Tan ◽  
Jian Ming Gong
Keyword(s):  
Fuel Cell ◽  
Surface Chemistry ◽  
Optical Microscopy ◽  
Silicone Rubber ◽  
Pem Fuel Cell ◽  
Sample Surface ◽  
Proton Exchange ◽  
Attenuated Total Reflection ◽  
Chemical Degradation ◽  
Over Time

The long term stability and durability of gaskets made of silicone rubber in proton exchange membrane fuel cell (PEMFC) has important effect on the sealing and the electric-chemical performance of the fuel cell. In present paper, the time-dependent chemical degradation of a silicone rubber was studied in three simulated PEMFC environments. The test temperature was selected and used at 90°C in this study according to the actual PEM fuel cell operation. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the gasket material before and after exposure to the simulated PEM fuel cell environments over time. The results show that the weight loss increased with the exposure time for the samples. Optical microscopy reveals that the surface conditions of the samples changed over time from initially smooth to rough, crack appearance and finally crack propagation. The ATR-FTIR results show that the surface chemistry changed significantly via de-crosslinking and chain scission in the backbone for the material over time.

scholarly journals On Measuring Flexural Properties of Ice Using Cantilever Beams

1983 ◽  
Vol 4 ◽  
pp. 58-65 ◽  
Author(s):  
R. M. W. Frederking ◽  
G. W. Timco
Keyword(s):  
Loading Rate ◽  
Ice Sheets ◽  
Elastic Beam ◽  
Beam Theory ◽  
Beam Width ◽  
Beam Deflection ◽  
Cantilever Beams ◽  
Beam Length ◽  
Fine Grained ◽  
Geometry Dependence

Tests have been performed on fine-grained, columnar, freshwater ice sheets 40 to 70 mm thick grown in a refrigerated model basin. Cantilever beams of various geometries were tested for lengths ranging from 200 to 2 000 mm and widths of 50 to 250 mm. Analysis of the results in terms of simple elastic beam theory indicated that modulus increased with increasing beam length and decreasing bean width. An analytical model for beam deflection was developed, taking into account the effects of buoyancy, shear, and rotation and deflection at the root. This model satisfactorily explained the observed deflection behaviour and the apparent geometry dependence of the modulus. Flexura! strength was independent of beam length, but decreased with increasing beam width. Flexural strength was independent of loading rate, whereas modulus decreased with increased loading time.

scholarly journals On Measuring Flexural Properties of Ice Using Cantilever Beams

1983 ◽  
Vol 4 ◽  
pp. 58-65 ◽  
Author(s):  
R. M. W. Frederking ◽  
G. W. Timco
Keyword(s):  
Loading Rate ◽  
Ice Sheets ◽  
Elastic Beam ◽  
Beam Theory ◽  
Beam Width ◽  
Beam Deflection ◽  
Cantilever Beams ◽  
Beam Length ◽  
Fine Grained ◽  
Geometry Dependence

Tests have been performed on fine-grained, columnar, freshwater ice sheets 40 to 70 mm thick grown in a refrigerated model basin. Cantilever beams of various geometries were tested for lengths ranging from 200 to 2 000 mm and widths of 50 to 250 mm. Analysis of the results in terms of simple elastic beam theory indicated that modulus increased with increasing beam length and decreasing bean width. An analytical model for beam deflection was developed, taking into account the effects of buoyancy, shear, and rotation and deflection at the root. This model satisfactorily explained the observed deflection behaviour and the apparent geometry dependence of the modulus. Flexura! strength was independent of beam length, but decreased with increasing beam width. Flexural strength was independent of loading rate, whereas modulus decreased with increased loading time.

scholarly journals Color models of interference images of thin stratified objects in optical microscopy

2019 ◽  
Vol 43 (6) ◽  
pp. 956-967
Author(s):  
A.A. Dyachenko ◽  
V.P. Ryabukho
Keyword(s):  
Optical Microscopy ◽  
Optical Thickness ◽  
Blood Cells ◽  
Measurement Method ◽  
Blood Smear ◽  
Color Model ◽  
Simulated Image ◽  
Pattern Processing ◽  
Lab Color Model ◽  
Interference Image

Algorithms for the analysis of polychromatic interference patterns in images of thin stratified objects in optical microscopy are considered. The algorithms allow one to measure the thin-film optical thickness. A measurement method based on the comparison of colors of the interference image under study and a numerically simulated image is discussed. We discuss a mathematical model for the calculation and numerical simulation of interference patterns and algorithms for interference pattern processing. Color comparison in an RGB color model is described and limitations of such a method are shown. The feasibility of using a Lab color model is shown and algorithms of interference color comparison in this model are presented. Results of application of the presented algorithms to measuring the optical thickness of red blood cells in a blood smear are discussed. The estimation of the error and robustness of the proposed algorithms is conducted.

Degradation of Gasket Materials in a Simulated Fuel Cell Environment

2006 ◽  
Author(s):  
Jinzhu Tan ◽  
Y. J. Chao ◽  
Woo-Kum Lee ◽  
C. S. Smith ◽  
J. W. Van Zee ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Surface Chemistry ◽  
Ftir Spectroscopy ◽  
Optical Microscopy ◽  
Polymer Electrolyte Membrane ◽  
Strain Analysis ◽  
Accelerated Aging ◽  
Chain Scission ◽  
Attenuated Total Reflection ◽  
Simulated Fuel

A Polymer Electrolyte Membrane (PEM) fuel cell stack requires elastomeric gaskets in each cell to keep the reactant gases within their respective regions. If any gasket degrades or fails, the reactant gases (O2 and H2) can leak overboard or mix with each other directly during operation or during standby, and affect the overall operation and performance of the fuel cell. The degradation of four commercial gasket materials was investigated in a simulated fuel cell environment in this study. In an effort towards predicting lifetime of fuel cells, two solutions and two temperatures were used in the short-term, accelerated aging tests. Bend-strip environment crack resistance tests were performed on samples with various bend angles. Weight loss was monitored and surface structure changes were examined using optical microscopy on the samples exposed to the simulated fuel cell environment for selected periods of time. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy was employed to study surface chemistry of the gasket materials before and after exposure to the simulated fuel cell environment over time. Stress and strain analysis was conducted using finite element method (FEM) to quantify the stress/state in test samples. The test results reveal that two silicone materials were degraded significantly while the other two did not show much degradation up to 42 weeks exposure to the simulated fuel cell environment. Optical microscopy and ATR-FTIR spectroscopy analysis indicate that the surface chemistry altered gradually via mechanisms involving de-cross linking and chain scission in the backbone. From experimental and numerical results, it is concluded that there is an interaction between chemistry and stress that appears to accelerate the degradation of the gasket materials in fuel cell environment.

Enhancing Quantum Dots for Bioimaging using Advanced Surface Chemistry and Advanced Optical Microscopy: Application to Silicon Quantum Dots (SiQDs)

2015 ◽  
Vol 27 (40) ◽  
pp. 6144-6150 ◽  
Author(s):  
Xiaoyu Cheng ◽  
Elizabeth Hinde ◽  
Dylan M. Owen ◽  
Stuart B. Lowe ◽  
Peter J. Reece ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Surface Chemistry ◽  
Optical Microscopy ◽  
Silicon Quantum Dots

scholarly journals Measuring Cognitive Engagement: An Overview of Measurement Instruments and Techniques

2021 ◽  
Vol 8 (3) ◽  
pp. 63-76
Author(s):  
Shan Lİ
Keyword(s):  
Measurement Method ◽  
Current Practice ◽  
Empirical Work ◽  
Cognitive Engagement ◽  
Self Report ◽  
Measurement Instruments ◽  
Comprehensive Understanding ◽  
Analytical Perspective ◽  
Instruments And Techniques ◽  
Physiological Sensors

This paper adopted an analytical perspective to review cognitive engagement measures. This paper provided a comprehensive understanding of the instruments/techniques used to measure cognitive engagement, which could assist researchers or practitioners in improving their measurement methodologies. In particular, we conducted a systematic literature search, based on which the current practice in measuring cognitive engagement was synthesized. We organized and aggregated the information of cognitive engagement measures by their types, including self-report scales, observations, interviews, teacher ratings, experience sampling, eye-tracking, physiological sensors, trace analysis, and content analysis. We provided a critical analysis of the strength and weaknesses of each measurement method. Recommendations for measuring cognitive engagement were also provided to guide future empirical work in a meaningful direction.

Fibronexus-Like Adhesion Sites are Present at the Invasive Zones of Human Epidermoid Carcinomas

1982 ◽  
Vol 40 ◽  
pp. 106-109
Author(s):  
Irwin I. Singer
Keyword(s):  
Cell Cycle ◽  
Serum Concentration ◽  
Substrate Binding ◽  
High Serum ◽  
Adhesion Sites ◽  
Substrate Adhesion ◽  
Focal Contacts ◽  
Adhesion Complex ◽  
Low Serum

Our previous results indicate that two types of fibronectin-cytoskeletal associations may be formed at the fibroblast surface: dorsal matrixbinding fibronexuses generated in high serum (5% FBS) cultures, and ventral substrate-adhering units formed in low serum (0.3% FBS) cultures. The substrate-adhering fibronexus consists of at least vinculin (VN) and actin in its cytoplasmic leg, and fibronectin (FN) as one of its major extracellular components. This substrate-adhesion complex is localized in focal contacts, the sites of closest substratum approach visualized with interference reflection microscopy, which appear to be the major points of cell-tosubstrate adhesion. In fibroblasts, the latter substrate-binding complex is characteristic of cultures that are arrested at the G1 phase of the cell cycle due to the low serum concentration in their medium. These arrested fibroblasts are very well spread, flattened, and immobile.

Sign in / Sign up

Export Citation Format

Share Document