Development of Versatile Mechanical Testing Machine for Sub-Micro-Sized Specimens

微(或纳米)机电系统(MEMS/NEMS)有望应用于微光子学和生物医疗设备，如用于电光通信的光开关和用于脑外科手术的微导管。在这种装置中使用的部件的大小被认为是亚微米到微米的数量级。因此，微尺度材料的力学性能评价对于此类MEMS/NEMS器件的实际应用是至关重要的。特别是，微尺寸元件的断裂和疲劳性能对实际MEMS/NEMS器件的结构完整性和长期可靠性至关重要。为了评估这种亚微米级试件的断裂和疲劳性能，我们研制了一种新型的亚微米级试件力学试验机，它可以对试件施加少量的静载荷和循环载荷。以薄膜为原料，采用聚焦离子束加工技术制备了悬臂梁型亚微米缺口样品。利用该试验机进行了疲劳裂纹扩展和断裂试验。我们能够测量试件的断裂韧性、疲劳寿命和疲劳裂纹扩展速率。该试验机非常适用于测定MEMS/NEMS应用中亚微米级试件的断裂和疲劳性能。

Micro (or nano) electromechanical systems (MEMS/NEMS) are expected to be applied to micro-photonics and bio-medical devices such as optical switches for electro-optical communications and micro-catheters for brain surgery. The size of the components used in such devices is considered to be in the order of submicrons to microns. Therefore, the evaluation of mechanical properties of micro-sized materials are essential for practical applications of such MEMS/NEMS devices. In particular, the fracture and fatigue properties of micro-sized components are of crucial importance to the structural integrity and long-term reliability of actual MEMS/NEMS devices. In order to evaluate fracture and fatigue properties of such submicro-sized specimens, we have developed a new type mechanical testing machine for submicro-sized specimens, which can apply small amount of static and cyclic loads to the specimens. Cantilever beam type submicron-sized specimens with notches were prepared from thin films by focused ion beam machining. Fatigue crack growth and fracture tests were carried out using the testing machine. We were able to measure fracture toughness, fatigue life and fatigue crack growth rate of the specimens. This testing machine is extremely useful for determing fracture and fatigue properties of submicron-sized specimens for MEMS/NEMS applications.