Development of Corrosion Fatigue Testing Machine for Micro-Sized Specimens for Bio-MEMS

MEMS（微机电系统）设备有望作为生物MEMS（诊断和治疗设备）用于人体，作为检测设备用于腐蚀性环境。在这种MEMS器件中使用的元件的尺寸被认为是在微米量级。这种尺寸比传统金属和合金的晶粒直径小。这种微尺寸材料的力学性能被认为不同于散装材料。此外，腐蚀的影响被认为更为突出，因为微尺寸试样的比表面积比体积试样大。MEMS器件中可能存在微米级的裂缝，因此裂缝腐蚀也很重要。因此，微尺寸材料的腐蚀疲劳性能对于设计用于腐蚀环境的MEMS器件和微机械非常重要。然而，对微尺寸材料的腐蚀疲劳性能进行深入研究的研究却很少。然而，对微尺寸试样进行腐蚀疲劳试验存在一些困难。也有必要澄清问题的方法，并找到他们的解决方案。研制了微尺寸试样疲劳试验机，对Ni-P非晶合金和304奥氏体不锈钢试样进行了空气和0.9% NaCl溶液中的腐蚀疲劳试验，研究了尺寸对腐蚀疲劳性能的影响。以Ni-P非晶合金薄膜和304奥氏体不锈钢薄片为材料，采用聚焦离子束加工方法制备了尺寸为10微米× 10微米× 50微米的悬臂梁型试样。空气环境下试样的疲劳寿命在10万次以上，而腐蚀环境下试样的疲劳寿命在1万次以下。观察到明显的环境对疲劳性能的影响。讨论了测试方法中存在的几个问题及解决方法。少

MEMS (Micro electro mechanical systems) devices are expected to be used in human body as Bio-MEMS (diagnosis and treatment devices) and in corrosive environments as inspection devices. The size of components used in such MEMS devices are considered to be in the order of microns. This size is smaller than the grain diameter in conventional metals and alloys. Mechanical properties of such micro-sized materials are considered to be different from those of bulk materials. In addition, the effect of corrosion is considered to be more prominent, because the specific surface area of micro-sized specimens is larger compared with that of bulk specimens. Crevices, the size of which is also in the order of microns, may exist in MEMS devices and thus crevice corrosion is also important. Therefore, corrosion fatigue properties of micro-sized materials are extremely important to design MEMS devices and micro-machines used in corrosive environments. However, there have been few studies that investiga … More te corrosion fatigue properties of micro-sized materials. However, there are several difficulties in corrosion fatigue tests on micro-sized specimens. It is also necessary to clarify the problems for the method and to find their solutions. In this investigation, we have developed a fatigue testing machine for micro-sized specimens, and corrosion fatigue tests for micro-sized Ni-P amorphous alloy and 304 austenitic stainless steel specimens have been carried out in air and 0.9% NaCl solution to investigate the size effects on corrosion fatigue properties. Specimens of cantilever-beam-type with dimensions of 10 microns × 10 microns × 50 microns were prepared from a Ni-P amorphous alloy thin film and a 304 austenitic stainless steel thin sheet by focused ion beam machining. The fatigue life of the specimen tested in air was more than 100,000 cycles, while that tested in the corrosive environment was less than 10,000 cycles. Distinct environmental effects on fatigue properties were observed. Several problems and solutions for the testing method were also discussed. Less