JILA researchers have engineered a short, flexible, reusable probe for the atomic force microscope (AFM) that enables state-of-the-art precision and stability in picoscale force measurements. Shorter, softer and more agile than standard and recently enhanced AFM probes, the JILA tips will benefit nanotechnology and studies of folding and stretching in biomolecules such as proteins and DNA.
An AFM probe is a cantilever, shaped like a tiny diving board with a small, atomic-scale point on the free end. To measure forces at the molecular scale in a liquid, the probe attaches its tip to a molecule such as a protein and pulls; the resulting deflection of the cantilever is measured. The forces are in the realm of piconewtons, or trillionths of a newton. One newton is roughly the weight of a small apple.
新的探针设计，描述ACS纳米，*是Jila研究小组最近在AFM技术方面的第三次进步。吉拉由美国国家标准技术研究所（NIST）和科罗拉多大学博尔德大学共同运营。
该小组先前通过使用激光束以感知运动**并从长探头尖端或悬臂上取出金色涂层以增强长期力稳定性。测量信号，并使用长悬臂会导致其他测量问题，例如对蛋白质展开（例如蛋白质展开）的反应较慢。
最新的修改克服了这些问题和其他问题，提高了精度，而不会丧失稳定性，速度或灵敏度。Jila研究人员使用聚焦的离子束在短的商业悬臂的中心切一个孔，并将其剩余的支撑结构变薄，从而减少了悬臂在表面附近的刚度和摩擦。结果是在AFM力量测量中分别是出色的长期稳定性和改善的短期精度。
JILA researchers also added a protective glass cap over the gold coating at the end of the cantilever to retain beneficial reflectivity, and then removed the remaining gold to gain force stability. The modified cantilever enables rapid, precise and stable force measurements across a broad range of operating frequencies.
“Previously, we had to average the Brownian (random) motion of our favorite cantilever for about 60 milliseconds to get a measurement that had a precision of 1 piconewton,” JILA/NIST biophysicist Tom Perkins says. “Now, we can get the same precision in 1 millisecond or so.”
吉拉研究人员对单分子研究显示出重大好处。例如，短而软的悬臂可以在蛋白质展开时迅速测量强力突然变化。蛋白质折叠是正确的生物学功能所必需的，并且错误折叠可能导致诸如阿尔茨海默氏症之类的疾病。新的悬臂匹配更硬，未修饰的悬臂的响应，但具有更高的稳定性和精度。力稳定性在此应用中至关重要，因为蛋白质折叠和展开速率对施加载荷中的微小变化（小于1 piconewton）呈指数敏感。新设备还可以跟踪短暂的纳米级事件，包括蛋白质折叠，超过数百秒，比以前可能更长。新设计也应适用于纳米级材料的机械性能的快速探测。
值得注意的是,新的斜面ilevers are robust enough to be reused for multiple days. Moreover, JILA researchers say the new design is simple and inexpensive to make, and thus, suitable for routine use.
“Amazingly, this project was spearheaded by a talented undergraduate. We hope other groups with similarly talented students will adopt these cantilevers. We certainly are,” Perkins said.
Filed Under:运动控制•电动机控制
