New Lab-On-A-Chip Research Integrates Microfluidics And Optical Trapping

Main Category: Medical Devices / Diagnostics
Article Date: 28 Oct 2007 - 10:00 PDT


Researchers at Cornell University for the first time have integrated optical functions with microfluidic ones, enabling the sorting of particles by light. Reported in the Oct. 29 issue of Optics Express, due out Monday, the Cornell team showcases a new design for a "lab-on-a-chip" structure that provides the ability to move or sort particles using light. In addition to the advance in telecom and datacom applications this brings, the new architecture also lends itself to applications in biodetection, including the sorting of viruses and protein recognition.

Summary

This novel architecture, created by lead researcher Michal Lipson and her group and David Erickson and his group, is made up of a field of solid core waveguides. The waveguides are fabricated from SU-8, a material whose mechanical hardness and chemical resistance make it a source for use in lab-on-chip analysis systems. The waveguides used in the device achieve a much more efficient sorting process, which enables trapping and sorting much smaller spheres with much lower intensities than what has been previously reported. By integrating these waveguides on a chip, a massive parallel sorting system may be created. This sorting system would allow for hundreds of measurements in parallel on a 1x1 cm chip, introducing a portable system that provides greater efficiency and lower cost than the current methodologies.

Key Findings

* This is the first demonstration of complete integration of planar optical waveguides with microfluidic ones.

* This integrated system allows researchers to use light to control the movement of particles in a pressure-driven flow.

* The planar optofluidic architecture developed represents a simple yet functional optical manipulation system for lab-on-chip applications.

* The use of planar photonic structures in microfluidic devices removes the need for table-top free-space optics, potentially reducing costs and increasing platform portability.

* Such a system could find application in high-stability particle trapping and sorting, but also in biodetection by exploiting the strong light interaction between the particle and the evanescent field.

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Paper

"Optofluidic trapping and transport on solid core waveguides within a microfluidic device," Optics Express, Vol. 15, Issue 22, pages 14322-14334.

Abstract

In this work we demonstrate an integrated microfluidic/photonic architecture for performing dynamic optofluidic trapping and transport of particles in the evanescent field of solid core waveguides. Our architecture consists of SU-8 polymer waveguides combined with soft lithography defined poly(dimethylsiloxane) (PDMS) microfluidic channels. The forces exerted by the evanescent field result in both the attraction of particles to the waveguide surface and propulsion in the direction of optical propagation both perpendicular and opposite to the direction of pressure-driven flow. Velocities as high as 28 ìm/s were achieved for 3 ìm diameter polystyrene spheres with an estimated 53.5 mW of guided optical power at the trapping location. The particle-size dependence of the optical forces in such devices is also characterized.

Source: Colleen Morrison
Optical Society of America

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