Electrical properties and shrinkage of carbonized photoresist films and the implications for carbon microelectromechanical systems devices in conductive media

Recent advances in fabricating 3D micro- and nanostructures using carbon microelectromechanical systems, or C-MEMS, has opened up a wide variety of new and exciting applications. The development of 3D C-MEMS has been catapulted forward by the use of transparent, high-viscosity resists such as SU-8. The electrical characteristics and shrinkage of various thickness carbon films derived from SU-8 and AZ P4620 are quantified and discussed in the context of the decomposition and carbonization mechanisms of epoxy and phenolic resins. Measurements obtained reveal a thickness dependence of the resistivity at lower carbonization temperatures but not much dependence at 1000 degrees C. Possible explanations for this low-temperature thickness dependence are given. The electrical characteristics of carbon films obtained from both types of photoresists carbonized at 1000 degrees C are very similar to that of glassy carbon. Simulations have been carried out to demonstrate the importance of the carbon resistivity for C-MEMS devices when used in conductive media. A method for simple optimization and verification of C-MEMS device designs for use in conductive media is introduced.close496

NT-4 Gene Expression of Male Wistar Rat’s Sciatic Nerve Fiber: The Effect of Decreased Activity on the Form of Spinal Nerve Ligation

Background & Objectives: Painful neuropathy is a state resulting from somatosensory disease or injury. Neurotrophins such as NT-4 are crucial for neural growth and development and protect the integrity of function and structure of nervous system. Paying heed to the importance of physical activity in neural plasticity, this study focuses on the investigation of chronic effect of decreased activity on the form of spinal nerve ligation on NT-4 gene expression of male Wistar rat&rsquo;s sciatic nerve fiber. Materials & Methods: Ten adult male Wistar rats in the weight range of 250&plusmn;30 gr were randomly divided into two groups, including one healthy control group (C) and one group with decreased physical activity (SNL). Over six weeks, neuropathic pain behavior tests were conducted continually in both groups. At the end of the sixth week, the changes in NT-4 gene expression in sciatic nerve were measured with Real time technique. Results: The behavioral tests demonstrated that spinal nerve ligation induced thermal hyperalgesia and mechanical allodynia in the SNL group. Decreased pain threshold was observed throughout the study period (p<0.05). Additionally, in comparison with the C group, NT-4 gene expression in sciatic nerve fiber was significantly higher in the SNL group (p<0.05). Conclusion: In the present study, it was discovered that the decreased activity in the form of SNL is associated with increased NT-4 gene expression in the experimental group. With respect to the physiologic functions of NT-4 in nervous system, this elevation is probably a mechanism for neurogenesis in the injured area, and based on the previous studies, it seems that the increased activity could enhance the increased NT-4 gene expression and accelerate neurogenesis

Elaboration and mechanical characterization of multi-phase alumina-based ultra-fine composites

Al2O3-10 vol.% YAG and Al2O3-10 vol.% ZrO2 bi-phase composites as well as Al2O3-5 vol.% YAG-5 vol.% ZrO2 tri-phase composite were developed by controlled sur- face modi\ufb01cation of an alumina powder with inorganic pre- cursors of the second phases. Green bodies were produced by dry pressing and slip casting and then sintered at 1500 \ub0C. In particular, slip casting led to fully dense, defect-free, and highly homogenous samples, made of a \ufb01ne dispersion of the second phases into the micronic alumina matrix, as observed by SEM. The mechanical characterization proved the pre- dominant role of the \ufb01nal density on the Vickers hardness, while the elastic modulus was affected by the volume fraction of the constituent phases, in fairly good agreement with the rule of mixture prediction. The fracture toughness values of the bi- and tri-phase materials were similar, and their crack paths revealed the importance of the thermal residual stresses at the matrix-reinforcement interfaces, promoting inter- granular propagation