2011.6
About Instruments Today No. 182
Methods for Evaluating Soft Materials/Tissues Mechanical Properties
Investigation of Mechanical Behavior of Soft Materials by Digital Image Correlation Method [ 下載 PDF ]
Wei-Chung Wang, Yi-Chieh Ho, Hung-Tsan Shen, Ting-Yu Chang, Ya-Hsin Chang, Chun-Sheng Tsao, Ting-Ying Wu, Bo-Fu Chen
In recent years, the rapid development of soft materials must give revolutionary impact on electronics and biomedical industries. If the mechanical behavior of the soft materials under various loads can be accurately measured, the key technology of electronics and biomedical industries can then be controlled. In this paper, to provide updated information to the readers, several practical examples of measuring mechanical behavior of soft materials at the Laboratory Photomechanics of the Department of Power Mechanical Engineering of National Tsing Hua University were introduced.
Modeling and Characterization of Polydimethylsiloxane (PDMS) Pillar Arrays for Biological Applications [ 下載 PDF ]
Yen-Ming Liao, Kuang-Shun Ou, I-Kuan Lin, Kuo-Shen Chen
The mechanical interaction force between cells and their neighboring extracellular matrix is believed to be very important in various physiological processes and which can be measured by soft material probes. Polydimethylsiloxane (PDMS) is an important polymeric material widely used in bio-MEMS devices such as micropillar arrays for cellular mechanical force measurements. The accuracy of such a measurement relies on choosing an appropriate material constitutive model for converting the measured structural deformations into corresponding reaction forces. However, although PDMS is a well-known viscoelastic material, many researchers in the past have treated it as a linear elastic material and employed the simple cantilever beam equation to calculate the force from observed defl ection, which could result in errors of cellular traction force interpretation. In this paper, the mechanical properties of PDMS were characterized by using uniaxial compression, dynamic mechanical analysis, and nanoindentation tests in both macro- and micro- scales, as well as finite element analysis. A generalized Maxwell model with the use of two exponential terms was used to emulate the mechanical behavior of PDMS at room temperature and the subsequent nanoindentation characterizations. After we found the viscoelastic constitutive law of PDMS, we used it to develop a more accurate model for converting defl ection data to cellular traction forces. The results indicate that the linear cantilever beam model could significantly overestimate the cellular forces. Furthermore, in situ cellular traction force evolutions of cardiac myocytes were demonstrated by using this new conversion model. The results presented by this paper are believed to be useful for biologists who are interpreting similar physiological processes.
Investigation of Fracture Properties of Gamma-Ray Polymerized Double-Network Hydrogels [ 下載 PDF ]
Ming-Hua He, Yao-Qi Lin, Nai-Shang Liou, Hong-Ru Lin, Guo-Wei Ruan
Hydrogels derive their name from their super absorbent natural. Hydrogels have inherently weak mechanical strength. However, the advantages of bio-compatibility and hydrophilicity make hydrogels become biomaterials for many biomedical applications. New developed high strength hydrogels have the potential to be used as artifi cial nucleus pulposus replacement in the cervical disk due to the properties of low friction and high mechanical strength. These potential applications necessitate closer investigation of mechanical properties of the candidate high strength hydrogels. In this study, a hybrid numerical/experimental J-integral method was developed to quantify fracture parameters of gamma ray synthesized high strength hydrogels.
Mechanical Testing of Biological Soft Tissues [ 下載 PDF ]
Yen-Ching Liu, Wei-Chih Chao, Jin-Jia Hu
Knowledge of mechanical properties of a soft tissue is essential to understand its functions during health and disease. Stress or strain fi elds in a soft tissue, which may be correlated with mechano-biological responses, cannot be analyzed without knowing its mechanical properties. However, it is generally challenging to characterize mechanical properties of soft tissues due to their special characteristics. In this article, two commonly used mechanical testing systems were described: one is for planar tissues and the other for cylindrical tissues. The corresponding stress and strain analysis was also introduced. The methods can be applied to not only soft tissues but also soft biomaterials such as hydrogels.
Optimization and Fabrication of High-Power Ultraviolet Q-switched Solid-State Laser [ 下載 PDF ]
Yu-Jen Huang, Cheng-Yu Tang, Kuan-Wei Su, Yung-Fu Chen
High-power ultraviolet laser plays an important role in a variety of scientific and industrial applications. In this report, optimization and fabrication of high-power ultraviolet Q-switched solid-state laser are introduced and investigated in detail. It is experimentally found that the parasitic lasing leads to the degradation of the actively Q-switched laser in high-power operation. We manifestly confirm that the combined effects of the parasitic lasing and the thermal lensing made Nd:YVO4 crystals with 0.1% dopant concentration to be more appropriate in designing a high-power Q-switched laser with a fl at-fl at cavity. We further use the optimized high-power actively Q-switched laser to perform the extra-cavity harmonic generations. At an incident pump power of 44 W, the output powers at 355 nm and 532 nm as high as 6.65 W and 8.38 W are obtained at a pulse repetition rate of 40 kHz. The optical-to-optical conversion effi ciencies from 808 nm to 355 nm and from 1064 nm to 355 nm are found to be up to 15.1% and 38.2%, respectively.
The System and the Mechatronics of a Pagoda Type Micro-CMM [ 下載 PDF ]
Kuang-Chao Fan, Hung-Yu Wang, Jyun-Kuan Ye, Chung-Hao Lin
This paper presents design considerations of a precision micro-CMM system and its mechatronics. The basic concept of design is to meet the requirements of high stiffness, force balance, thermal balance, Abbe principle, metrology frame and vibration free. Based on these criteria, a novel bridge designed in pagoda shape is proposed and analyzed by optimization to verify its superior stiffness with force balance and thermal balance structure due to its symmetrical geometry. A high precision Z-ram design with co-axial counterweight and vibration suppression is innovated. The design of a novel coplanar XY-stage that observes the rules of Abbe principle and symmetrical geometry is invented. This micro-CMM has measurement range of X: 20 mm, Y: 20 mm and Z: 10 mm. Equipped with an ultrasonic motor having nanomotion command and fed back by a diffraction interference scale with 1nm resolution, each axis can achieve long stroke and nano-positioning motion. Adding a developed contact scanning measuring probe to the spindle, this system is able to measure any geometry of the part to nanometer resolution.
X-ray Diffraction Analysis: Techniques and Applications [ 下載 PDF ]
Chun-Chuen Yang
X-ray diffraction is an important technique for the materials analysis. Since the end of 20th century, the improvement of computer technology making the quantitative analysis of the crystal structure becomes reality. Scholars can get more accurate crystal parameters of materials with structure refinements, and improve their understanding and analysis. The X-ray powder/polycrystal diffraction analysis techniques and theory will be fi rst introduced in this article. Furthermore, applications from these obtained crystal parameters will also be discussed and demonstrated.
LED Street Light Technology for Roadway Lighting Application [ 下載 PDF ]
Li-Ling Lee, Su-Chin Huang
Safety, energy conservation, intelligent and environmental friendly are roadway lighting basic requirements. The LED street light has the good light quality, the high effi ciency, easy to control and the long life. The LED street light luminous effi ciency has reached the 100 lm/W surmounting high pressure sodium lamp now, but the performance stability and reliability still have to improve. This paper introduces the regulations of roadway lighting, LED street light technology most recent development as well as application present situation in Taiwan, and also discusses the opportunity and the challenge of LED road lighting.
The Application of Vacuum Pump Performance Evaluation in Semiconductor and Electro-Optic Industries [ 下載 PDF ]
Fan-Chun Hsieh, Ping-Hung Lin, Jih-Ching Lu
Vacuum pumps have been widely used in semiconductor and electro-optic industries. Dry vacuum pumps become the main stream of the fi rst stage of the vacuum pumping for applications in clean room demand and semiconductor electro-optic requirement. The vacuum pump performance evaluation is a critical issue for the high-tech industries. The well-performance pumps can reduce containments, shorten pump-down time, and increase the process efficiency. This paper starts from the principle of vacuum pumps and introduces the performance evaluation technologies and analysis methods.
