Optical trapping of particles at the air/water interface for studies in Langmuir monolayers

A. Gutiérrez–Campos and R. Castillo

Instituto de Física, Universidad Nacional Autónoma de México, P.O. Box 20–264, México, 01000 D.F.

Recibido el 7 de abril de 2010
Aceptado el 8 de junio de 2010

Abstract

Optical experimental devices allow to observe and manipulate several micron–sized objects, for instance, condensed phase domains formed in Langmuir monolayers at the air/water interface. In this paper, an experimental instrument designed to trap and manipulate those domains is presented. This instrument consists of optical tweezers, colloidal beads as handles and Brewster angle microscopy (BAM) to observe the trapped domains. With this instrument it was possible to trap and observe small domains (20 — 30 μm) of nervonic acid monolayers.

Keywords: Optical trapping; optical tweezers; Langmuir monolayers.

Resumen

Los dispositivos experimentales ópticos permiten observar y manipular diversos objetos de escalas microscópicas como, por ejemplo, dominios de fases condensadas formados en monocapas de Langmuir en la intercara aire/agua. En este artículo se presenta un instrumento experimental diseñado para atrapar y manipular dichos dominios utilizando pinzas (ópticas, microesferas coloidales como sujetadores y microscopía de ángulo de Brewster (MAB) para observarlos. Con este instrumento fue posible atrapar y observar dominios pequeños (20 — 30 μm) de monocapas de ácido nervónico.

Descriptores: Atrapamiento óptico; pinzas ópticas; monocapas de Langmuir.

PACS: 87.80.Cc; 82.70.Dd

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Acknowledgment

The support from SEP–CONACYT (81081) and DGAPA–UNAM (112508) is gratefully acknowledged. We also thank to C. Garza and S. Ramos for their technical support in optical alignment and monolayer development.

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