There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices. Here we present a new on-chip microelectromechanical system (MEMS) for high strain-rate nanomechanical testing. The MEMS device consists of an electrostatic comb drive actuator, two capacitive displacement sensors and a load cell. The dynamic responses of the device in air and in vacuum are systematically modeled under both alternating and ramp forces. Two methods, capacitive readout and high-speed imaging, are used to measure the dynamic displacements, which agree well with the modeling results. While we demonstrate the maximum constant strain rate over 200 s −1 under ramp force, it is interesting to find that the capacitive readout used in this work can only measure strain rate up to 22 s −1 due to its limit in bandwidth. To demonstrate the utility of this new device, gold nanowires are tested at strain rates of 10 −5 and 10 s −1 inside a scanning electron microscope. Increasing strain rate is found to yield higher yield strength and larger ductility.

中文翻译：

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用于纳米机械测试的微机电系统：用于高应变率测试的静电驱动和电容传感

关于高应变率下纳米材料力学性能的研究相对较少，主要是由于缺乏有效的纳米力学测试设备。在这里，我们提出了一种用于高应变率纳米机械测试的新型片上微机电系统 (MEMS)。MEMS 设备由一个静电梳状驱动执行器、两个电容位移传感器和一个称重传感器组成。设备在空气和真空中的动态响应在交替力和斜坡力下系统地建模。两种方法，电容读出和高速成像，用于测量动态位移，这与建模结果非常吻合。虽然我们证明了在斜坡力下超过 200 s -1 的最大恒定应变率，有趣的是，由于带宽的限制，这项工作中使用的电容读数只能测量高达 22 s -1 的应变率。为了证明这种新装置的实用性，在扫描电子显微镜内以10 -5 和10 s -1 的应变率测试金纳米线。发现增加应变速率会产生更高的屈服强度和更大的延展性。