Schein Perry, Kang Pilgyu, O'Dell Dakota, Erickson David
Sibley School of Mechanical and Aerospace Engineering, Cornell University , Ithaca, New York 14853, United States.
Nano Lett. 2015 Feb 11;15(2):1414-20. doi: 10.1021/nl504840b. Epub 2015 Jan 28.
Direct measurements of particle-surface interactions are important for characterizing the stability and behavior of colloidal and nanoparticle suspensions. Current techniques are limited in their ability to measure pico-Newton scale interaction forces on submicrometer particles due to signal detection limits and thermal noise. Here we present a new technique for making measurements in this regime, which we refer to as nanophotonic force microscopy. Using a photonic crystal resonator, we generate a strongly localized region of exponentially decaying, near-field light that allows us to confine small particles close to a surface. From the statistical distribution of the light intensity scattered by the particle we are able to map out the potential well of the trap and directly quantify the repulsive force between the nanoparticle and the surface. As shown in this Letter, our technique is not limited by thermal noise, and therefore, we are able to resolve interaction forces smaller than 1 pN on dielectric particles as small as 100 nm in diameter.
直接测量颗粒与表面之间的相互作用对于表征胶体和纳米颗粒悬浮液的稳定性及行为非常重要。由于信号检测极限和热噪声，当前技术在测量亚微米颗粒上皮牛顿尺度相互作用的能力方面受到限制。在此，我们展示了一种用于在该领域进行测量的新技术，我们将其称为纳米光子力显微镜。利用光子晶体谐振器，我们生成了一个呈指数衰减的强局部近场光区域，这使我们能够将小颗粒限制在靠近表面的位置。根据颗粒散射光强度的统计分布，我们能够绘制出陷阱的势阱，并直接量化纳米颗粒与表面之间的排斥力。如本信函所示，我们的技术不受热噪声限制，因此，我们能够分辨直径小至100 nm的介电颗粒上小于1 pN的相互作用力。
