An integrated open source acoustofluidic platform using surface acoustic waves for biomedical applications

Surface acoustic wave (SAW) devices using thin film technology are increasingly used in lab-on-a-chip, point-of-care and a wide variety of biomedical applications, due to their multi-functionalities and low cost. These thin film devices not only have both acoustofluidic sensing and actuation functions, but also have been produced with commonly used semiconductor manufacturing techniques. These allow the acoustic devices to be made on many different substrates, such as aluminium plate and foils, glass, silicon, polymers and plastics, which provide a wide variety of properties enabling many new directions and opening up new applications. However, acoustic wave technology still requires benchtop lab equipment and experienced operators to utilise these SAW devices because of a lack of hardware integration and autonomous control, resulting in a higher-cost system than the proposed platform. Most SAW interfacing setups are bulky and complex to use. There are currently many studies exploring the uses of mobile phones, cameras and attempting to use open-source electronics to generate and control acoustic waves. In this thesis, we combine SAW microfluidics and sensing with Raspberry-Pi hardware, making a full use of its digital imaging capabilities. This thesis focuses on integrating surface acoustic wave devices and open-source hardware and software to overcome the challenges with a digitally controlled acoustofluidic platform. The aim of this modular platform is to perform acoustofluidic functions autonomously, such as droplet transportation, mixing, heating and sensing. The basis of this platform is a Raspberry Pi, together with piezoelectric thin films on metallic substrates, 3D printed housing and additional electronics for SAW device control. The setup is then used to demonstrate these functions applied in a variety of biomedical applications, such as disease diagnostics, breathing disorder monitoring and cell culturing

Apnoea-Pi: Sleep disorder monitoring with open-source electronics and acoustics

Apnoea is a sleep disorder that affects an increasing number of adults causing harm from fatigue to a growing chance of heart problems. Apnoea disorders can be treated but advanced monitoring and diagnosing tools are needed to identify its strand and offer adequate treatment. Therefore, Apnoea tracking is vital to help keep patients healthy. Sleep Apnoea can cause a number of conditions such as fatigue, high blood pressure, liver functionality and an increased risk of type 2 diabetes. These complications make it necessary to monitor as many potential patients as possible by designing an instrument that is accurate, comfortable to use, fit for purpose, cost effective and with embedded computation capabilities to store, process and transmit time series data. In this work we present Apnoea-Pi, an adaptation of our Acousto-Pi open source surface acoustic wave platform to monitor Apnoea in patients using ultrasonic humidity sensing

Acousto-Pi: An Opto-Acoustofluidic System using Surface Acoustic Waves controlled with Open Source Electronics for Integrated In-Field Diagnostics

Surface acoustic wave (SAW) devices are increasingly applied in life science, 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 3D printed housing, and the SAW devices are fabricated with piezoelectric thin film 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 towards integrated in-field diagnostic applications such as disease outbreak control, mass healthcare screening and food safety

Overview of Space-Based Laser Communication Missions and Payloads: Insights from the Autonomous Laser Inter-Satellite Gigabit Network (ALIGN)

This paper examines the growing adoption of laser communication (lasercom) in space missions and payloads for identifying emerging trends and key technology drivers of future optical communications satellite systems. It also presents a comprehensive overview of commercially available and custom-designed lasercom terminals, outlining their characteristics and specifications to meet the evolving demands of global satellite networks. The analysis explores the technical considerations and challenges associated with integrating lasercom terminals into LEO constellations and the Inter-satellite communications service provision in LEO due to their power, size, and weight constraints. By analyzing advancements in CubeSat lasercom technology designed to cater for the emergence of future mega constellations of interacting small satellites, the paper underscores its promising role in establishing high-performance satellite communication networks for future space exploration and data transmission. In addition, a brief overview of our ALIGN planned mission is provided, which highlights the main key operational features in terms of PAT and link budget analysis

Integrated sensing and acoustofluidic functions for flexible thin film acoustic wave devices based on metallic and polymer multilayers

Surface acoustic wave (SAW) devices are generally fabricated on rigid substrates that support the propagation of waves efficiently. Although very challenging, the realisation of SAW devices on bendable and flexible substrates can lead to new generation SAW devices for wearable technologies. In this paper, we report flexible acoustic wave devices based on ZnO thin films coated on various substrates consisting of thin layers of metal (e.g., Ni/Cu/Ni) and/or polymer (e.g., polyethylene terephthalate, PET). We comparatively characterise the fabricated SAW devices and demonstrate their sensing applications for temperature and ultraviolet (UV) light. We also investigate their acoustofluidic capabilities on different substrates. Our results show that the SAW devices fabricated on a polymer layer (e.g. ZnO/PET, ZnO/Ni/Cu/Ni/PET) show enhanced temperature responsivity, and the devices with larger wavelengths are more sensitive to UV exposure. For actuation purposes, the devices fabricated on ZnO/Ni/Cu/Ni layer have the best performance for acoustofluidics, whereas insignificant acoustofluidic effects are observed with the devices fabricated on ZnO/PET layers. We propose that the addition of a metallic layer of Ni/Cu/Ni between ZnO and polymer layers facilitates the actuation capability for the acoustofluidic applications while keeping temperature and UV sensing capabilities, thus enhancing the integration of sensing and acoustofluidic functions

Flexible and integrated sensing platform of acoustic waves and metamaterials based on polyimide coated woven carbon fibers

Versatile, in situ sensing and continuous monitoring capabilities are critically needed but challenging for components made of solid woven carbon fibers in aerospace, electronics and medical applications. In this work, we proposed a unique concept of integrated sensing technology on woven carbon fibers through integration of thin film surface acoustic wave (SAW) technology and electromagnetic metamaterials, with capabilities of non-invasive, in-situ and continuous monitoring of environmental parameters and biomolecules wirelessly. Firstly, we fabricated composite materials using a three-layer composite design, in which the woven carbon fiber cloth was firstly coated with a polyimide (PI) layer followed by a layer of ZnO film. Integrated SAW and metamaterials devices were then fabricated on this composite structure. Temperature of the functional area of the device can be controlled precisely using the SAW devices, which can provide a proper incubation environment for biosampling processes. As a demonstration for an ultraviolet light sensor, the SAW device could achieve a good sensitivity of 56.86 ppm/(mW∙cm-2). On the same integrated platform, the electromagnetic resonator based on the meta-materials has been demonstrated to work as a glucose concentration monitor with a sensitivity of 0.34 MHz/(mg/dL)

Breath monitoring, sleep disorder detection and tracking using thin film acoustic waves and open-source electronics

Apnoea, a major sleep disorder, has affected many adults and caused several issues, such as fatigue, high blood pressure, liver conditions, increased risk of type II diabetes and heart problems. Therefore, advanced monitoring and diagnosing tools of apnoea disorders are needed to facilitate better treatments, with advantages such as accuracy, comfort of use, cost effectiveness and embedded computation capabilities to recognise, store, process and transmit time series data. In this work we present an adaptation of our Acousto-Pi open-source Surface Acoustic Wave (SAW) platform (Apnoea-Pi), to monitor and recognise apnoea in patients. The platform is based on thin film SAW, using bimorph ZnO and aluminium structures, including those fabricated in Al foils or plates, to achieve for breath tracking based on the humidity and temperature changes. We applied open-source electronics and provided embedded computing characteristics for signal processing, data recognition, storage, and transmission of breath signals. We show that thin film SAW devices out-perform standard and off-the-shelf capacitive electronic sensors regarding to their responses and accuracy for human breath tracking purposes. This in combination with embedded electronics makes a suitable platform for human breath monitoring and sleep disorder recognition

A rapid and controllable acoustothermal microheater using thin film surface acoustic waves

Temperature control within a microreactor is critical for biochemical and biomedical applications. Recently acoustothermal heating using surface acoustic wave (SAW) devices made of bulk LiNbO3 substrates have been demonstrated. However, these are generally fragile and difficult to be integrated into a single lab-on-a-chip. In this paper, we propose a rapid and controllable acoustothermal microheater using AlN/Si thin film SAWs. The device's acoustothermal heating characteristics have been investigated and are superior to other types of thin film SAW devices (e.g., ZnO/Al and ZnO/Si). The dynamic heating processes of the AlN/Si SAW device for both the sessile droplet and liquid within a polydimethylsiloxane (PDMS) microchamber were characterized. Results show that for the sessile droplet heating, the temperature at a high RF power is unstable due to significant droplet deformation and vibration, whereas for the liquid within the microchamber, the temperature can be precisely controlled by the input power with good stability and repeatability. In addition, an improved temperature uniformity using the standing SAW heating was demonstrated as compared to that of the travelling SAWs. Our work shows that the AlN/Si thin film SAWs have a great potential for applications in microfluidic heating such as accelerating biochemical reactions and DNA amplification

A rapid and controllable acoustothermal microheater using thin film surface acoustic waves

Temperature control within a microreactor is critical for biochemical and biomedical applications. Recently acoustothermal heating using surface acoustic wave (SAW) devices made of bulk LiNbO3 substrates have been demonstrated. However, these are generally fragile and difficult to be integrated into a single lab-on-a-chip. In this paper, we propose a rapid and controllable acoustothermal microheater using AlN/Si thin film SAWs. The device’s acoustothermal heating characteristics have been investigated and are superior to other types of thin film SAW devices (e.g., ZnO/Al and ZnO/Si). The dynamic heating processes of AlN/Si SAW devices for both a sessile droplet and liquid within a polydimethylsiloxane (PDMS) microchamber were characterized. Results show that for the sessile droplet heating, the temperature at a high RF power is unstable due to significant droplet deformation and vibration, whereas for the liquid within the microchamber, the temperature can be precisely controlled by the input power with good stability and repeatability. In addition, an improved temperature uniformity using the standing SAW heating was demonstrated as compared to that of the travelling SAWs. Our work shows that the AlN/Si thin film SAWs have a great potential for applications in microfluidic heating such as accelerating biochemical reactions and DNA amplification

Integrated sensing and acoustofluidic functions for flexible thin film acoustic wave devices based on metallic and polymer multilayers

Surface acoustic wave (SAW) devices are generally fabricated on rigid substrates that support the propagation of waves efficiently. Although very challenging, the realisation of SAW devices on bendable and flexible substrates can lead to new generation SAW devices for wearable technologies. In this paper, we report flexible acoustic wave devices based on ZnO thin films coated on various substrates consisting of thin layers of metal (e.g., Ni/Cu/Ni) and/or polymer (e.g., polyethylene terephthalate, PET). We comparatively characterise the fabricated SAW devices and demonstrate their sensing applications for temperature and ultraviolet (UV) light. We also investigate their acoustofluidic capabilities on different substrates. Our results show that the SAW devices fabricated on a polymer layer (e.g. ZnO/PET, ZnO/Ni/Cu/Ni/PET) show enhanced temperature responsivity, and the devices with larger wavelengths are more sensitive to UV exposure. For actuation purposes, the devices fabricated on ZnO/Ni/Cu/Ni layer have the best performance for acoustofluidics, whereas insignificant acoustofluidic effects are observed with the devices fabricated on ZnO/PET layers. We propose that the addition of a metallic layer of Ni/Cu/Ni between ZnO and polymer layers facilitates the actuation capability for the acoustofluidic applications while keeping temperature and UV sensing capabilities, thus enhancing the integration of sensing and acoustofluidic functions.</p