Real-time precise microfluidic droplets label-sequencing combined in a velocity detection sensor

R Zamboni,M Chauvet,C Sada,A Zaltron

doi:10.1038/s41598-021-97392-3

Abstract

Droplets microfluidics is broadening the range of Lab on a Chip solutions that, however, still suffer from the lack of an adequate level of integration of optical detection and sensors. In fact, droplets are currently monitored by imaging techniques, mostly limited by a time-consuming data post-processing and big data storage. This work aims to overcome this weakness, presenting a fully integrated opto-microfluidic platform able to detect, label and characterize droplets without the need for imaging techniques. It consists of optical waveguides arranged in a Mach Zehnder’s configuration and a microfluidic circuit both coupled in the same substrate. As a proof of concept, the work demonstrates the performances of this opto-microfluidic platform in performing a complete and simultaneous sequence labelling and identification of each single droplet, in terms of its optical properties, as well as velocity and lengths. Since the sensor is realized in lithium niobate crystals, which is also highly resistant to chemical attack and biocompatible, the future addition of multifunctional stages into the same substrate can be easily envisioned, extending the range of applicability of the final device.

Highlights

Droplets microfluidics is broadening the range of Lab on a Chip solutions that, still suffer from the lack of an adequate level of integration of optical detection and sensors
The Mach–Zehnder interferometer (MZI) configuration gives a univocally description of each droplet of a sequence, thanks to the fact that the trigger times of the optical transmission (OT) signal can be associated to a well-defined configuration (a, b, c), the optofluidic device can be employed to recognize and label sequence of droplets presenting arbitrary properties, both in shape or size
It consists of an Integrated Mach–Zehnder (MZI) waveguides configuration orthogonally crossed by a microfluidic channel

Summary

Introduction

Droplets microfluidics is broadening the range of Lab on a Chip solutions that, still suffer from the lack of an adequate level of integration of optical detection and sensors. The most common systems for the tracking and labelling purposes involve microscopy and fast cameras for the recording of several frames of the same droplet, and postprocessing tools for the imaging analysis This standard method is popular due its good performances and the commercial availability of the required instruments, the post-processing times and the bulkiness of the setup are hindering the strengths of the lab-on-a-chip, their portability, as well as the plug&play structure. The most successful approach consists in the optical sensing[23,24,25,26,27,28,29], which are often based on two measurements carried out in different positions of the channel, where the droplets flows[24,25] These systems currently exploit optical fibers, which led to a step towards the integration and portability of lab-on-a-chips. This step has been recently overcome by the development of integrated optical waveguides, that ensure to transport and collect light across the channel with high reproducibility of the alignment[30,31,32,33,34,35,36,37]

Objectives

Methods

Results

Conclusion