Advanced Materials Research Vol. 411

Abstract: With the development of nano materials, a novel research field of NEMS forms by combining nano materials, nano-structures and nano fabrication with MEMS. Carbon nanotube (CNT) is a kind of one-dimensional nano structures which has unique mechanical, electrical and chemical properties. Using CNTs, new nano-devices with new principle or high performance would be developed. This paper reviews the assembly methods of one dimensional nanostructure and analyzes the characteristics of various methods, which provides reference for the device manufacturing methods using nanotubes/nanowires.

Abstract: Detector diodes have been successfully used in differential capacitive MEMS accelerometer for capacitance-to-voltage conversion. During capacitances’ charging and discharging, charge accumulation makes test results disagree with the calculated values based on its differential equations simply and finally has a great influence on circuit’s optimization. A model of charges accumulation process is built to describe the real conversion relationship between the value of capacitance variations and the output voltage. Experiments show that the model not only meets the test result well but also provides a foundation for circuit’s optimization.

Abstract: It has been proved by large number of experiments that gas film damping has great influence on MEMS structures. Based on the elastic and material mechanics, this paper built a linear-vibration model for the electrostatic actuated micro-beam. According to the rarefied gas dynamics theory, a kind of modified Reynolds equation is adopted in the system modeling. In view of the study on small deflection of micro-beam has been investigated already by many researchers, this paper focus the research on large beam deflections, i.e. the mid-point deflection can be compared with the thickness of the gas film. The dynamic characteristics of micro-beam are investigated through coupling the dynamic vibration equation with the modified Reynolds equation. Through the finite difference method, the discrete form of the coupled dynamic equations has been obtained.

Abstract: With the development of MEMS technology and its increasing applications in many engineering fields, the experimental research on micro-scale fluidic theory has become a spotlight topic in the past decade. In this paper, numerical and experimental investigations on the effects of roughness, compressibility and gas rarefaction on the nitrogen flow in rough microchannels had been investigated. Microchannels based on silicon substrates were fabricated by the MEMS process. Roughness surfaces of the microchannels had been obtained by KOH and TMAH solutions with different solubility etching on (100) silicon wafer. The quality of the microchannels was performed with a SEM and the measurements and the overall size of the microchannels were carried out with a step profiler. The Pyrex® 7740 and silicon wafers were packaged using the anodic bonding method. The testing platform was designed and fabricated, and checked for the gas sealing. Finally, the experimental device was constructed, and the results of gas flow in rough microchannels were measured.

Abstract: In the treatment of nerve disorders, bio-electrodes are used to be implanted into the patients’ deep brain to provide electrical stimulation to improve the symptom and deep brain stimulation has been regarded as the most effective method to treat nerve disorders in clinic medicine. This paper presented a simple structure of bio-electrode implanted in deep brain for long term stimulation. Based on a 3D finite element modeling of electrostatics for the electrode, the influence of the electrode dimensions on the electric field distribution was discussed. The dimension and structure of the electrode was determined on the volume of tissue activated by deep brain stimulation.

Abstract: The military ballistic characteristics of a new kind of non-silicon MEMS inertia trigger switch were investigated by finite element method (FEM) in this paper. Some useful results on the ballistic characteristics were obtained and the non-silicon MEMS inertia switch was proved to be highly reliable and sensitive eventually.

Abstract: Due to deformation of the cantilever and lock, the MEMS explosion interrupter used in fuze often cannot move properly. An explosion interrupter with improved strength is proposed. The caudal shape of the cantilever is improved and its structure is changing from the straight hook to the bend hook. The thickness and the patulous angle of the lock is enhanced. Simulation results show that the improved caudal shape of the cantilever is not stuck by the baseplate boss and the improved lock could enter into the locker successfully. The explosion interrupter moves in-position under centrifugal force and be locked.

Abstract: Measurement of axial acceleration is necessary for projectile range prediction. Three measurement methods, dual-accelerometer configuration, dual-accelerometer filtering and direct filtering, are used to eliminate acceleration measurement errors caused by accelerometer configuration location, installation errors and space rotating of projectiles. Based on six-degree ballistic trajectory model, the three measurement methods of projectile axial acceleration are simulated, and the simulation results show that standard deviation of dual-accelerometer configuration measurement error is 35.7318, while standard deviation of dual-accelerometer filtering measurement error is 2.2958 and direct filtering measurement error is 0.3344.

Abstract: Boundary tracing method is an important preprocessing instrument for image recognition and image measurement, but the traditional boundary tracing method exits a conflict between the veracity and the speed. In response to these problems, we propose the boundary tracking algorithm based on the model, and then obtain the tool diameter. Experiments show that the boundary tracking algorithm can achieve a good boundary track. Compared two algorithms of diameter measurements, we obtain that the least square method runs shorter, and more efficient.

Abstract: This paper describes a simple and effective lift-off method that relies upon a single layer of positive photoresist and lithography technology. We have succeeded in patterning narrow lines in a photoresist film by image reversal process. Image reversal with AZ 5214-E resist is characterized by contact lithography. A process of patterning different line widths was developed based on image reversal technology, using AZ5214-E, followed by pre-bake, exposure, reversal bake, flood exposure and development. We could obtain very neat patterns with 2-5μm dimensions and their relative features have been supported by scanning electron microscope (SEM) pictures. The application of the proposed process is suitable for the electrode fabrication in MEMS SAW devices.