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An optofluidic “tweeze-and-drag” cell stretcher in a microfluidic channel

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Abstract

The mechanical properties of biological cells are utilized as an inherent, label-free biomarker to indicate physiological and pathological changes of cells. Although various optical and microfluidic techniques have been developed for cell mechanical characterization, there is still a strong demand for non-contact and continuous methods. Here, by combining optical and microfluidic techniques in a single desktop platform, we demonstrate an optofluidic cell stretcher based on a “tweeze-and-drag” mechanism using a periodically chopped, tightly focused laser beam as an optical tweezer to trap a cell temporarily and a flow-induced drag force to stretch the cell in a microfluidic channel transverse to the tweezer. Our method leverages the advantages of non-contact optical forces and a microfluidic flow for both cell stretching and continuous cell delivery. We demonstrate the stretcher for mechanical characterization of rabbit red blood cells (RBCs), with a throughput of ∼1 cell per s at a flow rate of 2.5 μl h−1 at a continuous-wave laser power of ∼25 mW at a wavelength of 1064 nm (chopped at 2 Hz). We estimate the spring constant of RBCs to be ∼14.9 μN m−1. Using the stretcher, we distinguish healthy RBCs and RBCs treated with glutaraldehyde at concentrations of 5 × 10−4% to 2.5 × 10−3%, with a strain-to-concentration sensitivity of ∼−1529. By increasing the optical power to ∼45 mW, we demonstrate cell-stretching under a higher flow rate of 4 μl h−1, with a higher throughput of ∼1.5 cells per s and a higher sensitivity of ∼−2457. Our technique shows promise for applications in the fields of healthcare monitoring and biomechanical studies.

Graphical abstract: An optofluidic “tweeze-and-drag” cell stretcher in a microfluidic channel

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Supplementary files

Article information


Submitted
15 Oct 2019
Accepted
19 Dec 2019
First published
24 Dec 2019

This article is Open Access

Lab Chip, 2020, Advance Article
Article type
Paper

An optofluidic “tweeze-and-drag” cell stretcher in a microfluidic channel

Z. Yao, C. C. Kwan and A. W. Poon, Lab Chip, 2020, Advance Article , DOI: 10.1039/C9LC01026B

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