Acousto-Pi: An Opto-Acoustofluidic System Using Surface Acoustic Waves Controlled With Open-Source Electronics for Integrated In-Field Diagnostics.

Jethro Vernon,Pep Canyelles-Pericas,Yong-Qing Fu,Krishna Busawon,Xuewu Dai,Richard Binns,Wai Pang Ng,Hamdi Torun

doi:10.1109/tuffc.2021.3113173

Abstract

Surface acoustic wave (SAW) devices are increasingly applied in life sciences, biology, and point-of-care applications due to their combined acoustofluidic sensing and actuating properties. Despite the advances in this field, there remain significant gaps in interfacing hardware and control strategies to facilitate system integration with high performance and low cost. In this work, we present a versatile and digitally controlled acoustofluidic platform by demonstrating key functions for biological assays such as droplet transportation and mixing using a closed-loop feedback control with image recognition. Moreover, we integrate optical detection by demonstrating in situ fluorescence sensing capabilities with a standard camera and digital filters, bypassing the need for expensive and complex optical setups. The Acousto-Pi setup is based on open-source Raspberry Pi hardware and 3-D printed housing, and the SAW devices are fabricated with piezoelectric thin films on a metallic substrate. The platform enables the control of droplet position and speed for sample processing (mixing and dilution of samples), as well as the control of temperature based on acousto-heating, offering embedded processing capability. It can be operated remotely while recording the measurements in cloud databases toward integrated in-field diagnostic applications such as disease outbreak control, mass healthcare screening, and food safety.

Highlights

In order to manage disease outbreaks and reduce its rapid spreading; fast, accurate and affordable diagnostics techniques are needed
polymerase chain reaction (PCR) is widely accepted as the gold standard diagnostic method of detection of viral DNA/RNA, including COVID-19 [3], whereas loopmediated isothermal amplification (LAMP) is emerging as an alternative technique that offers comparable performance [4]
Separate signal sources and PID controllers are used with multiple interdigitated transducers (IDTs) allowing the droplet to be propelled diagonally

Summary

Introduction

In order to manage disease outbreaks and reduce its rapid spreading; fast, accurate and affordable diagnostics techniques are needed. The most established techniques for medical diagnostics based on nucleic acid (DNA and RNA) detection are polymerase chain reaction (PCR) and loopmediated isothermal amplification (LAMP) [1]. Both PCR and LAMP facilitate biological reactions that result in exponential amplification of targeted DNA for a subsequent detection step [2]. Different acoustofluidic functions in microfluidics, including generation, pumping, splitting, jetting, mixing and heating of droplets have been realised [25] Their integration into a single, low cost and efficient platform provided with a simple and low-cost optical detection for biological assays remains a challenge that this work aims to fulfil. The setup presented here can be used in the field directly, and the test result can be

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