Article:  Schein, P; Kang, P; O’Dell, D; Erickson, D; (2015) “Nanophotonic Force Microscopy: Characterizing Particle-Surface Interactions Using Near-Field Photonics”, Nano Letters,15 (2):1414-1420
DOI
Abstract:  Direct measurements of particlesurface 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.

 

Funding Acknowledgement:  U.S. Department of Energy Office of Basic Science [DE-SC0003935]; US National Institutes of Health [1R01GM106420-01]; US National Science Foundation [ECCS-0335765]

Funding Text:  The theory developed above and most of the experimental work was supported by the U.S. Department of Energy Office of Basic Science under Grant DE-SC0003935. Parts of this work were also supported by the US National Institutes of Health under grant 1R01GM106420-01. The photonic crystal resonator devices used in this work were fabricated at the Cornell NanoScale Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the US National Science Foundation (Grant ECCS-0335765). Zeta potential measurements were performed in the Nanobiotechnology Center shared research facilities at Cornell. We would also like to thank Dr. Bernardo Cordovez and Dr. Christopher Earhart from Optofluidics, Inc., for useful discussions and confirmatory experiments.