A tunable line optical tweezers instrument with nanometer spatial resolution

We describe a simple scanning-line optical tweezers instrument for measuring pair interactions between micrometer-sized colloidal particles. Our instrument combines a resonant scanning mirror and an acousto-optic modulator. The resonant scanning mirror creates a time-averaged line trap whose effecti...

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Bibliographic Details
Published in:Review of scientific instruments 2014-04, Vol.85 (4), p.043704-043704
Main Authors: Rogers, W Benjamin, Crocker, John C
Format: Article
Language:English
Subjects:
Acoustooptical devices
Confining
Contact potentials
Measuring instruments
Optics
Potential energy
Scanning
Scientific apparatus & instruments
Spatial resolution
Spring constant
Trapped particles
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Description
Summary:We describe a simple scanning-line optical tweezers instrument for measuring pair interactions between micrometer-sized colloidal particles. Our instrument combines a resonant scanning mirror and an acousto-optic modulator. The resonant scanning mirror creates a time-averaged line trap whose effective one-dimensional intensity profile, and corresponding trapping potential energy landscape can be programmed using the acousto-optic modulator. We demonstrate control over the confining potential by designing and measuring a family of one-dimensional harmonic traps. By adjusting the spring constant, we balance scattering-induced repulsive forces between a pair of trapped particles, creating a flat potential near contact that facilitates interaction measurements. We also develop a simple method for extracting the out-of-plane motion of trapped particles from their relative brightness, allowing us to resolve their relative separation to roughly 1 nm.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.4870806