This study presents an AlN based Lamb wave (A0 mode) liquid sensing device that can be used for biomedical applications. The Lamb wave device features a 1.5 μm composite membrane consisting of a 500 nm LPCVD SiN and a 1 μm of a c-axis oriented AlN film. A 45° rotated design was also considered for this project to reduce the reflections from the edges towards the output IDT. A liquid testing experiment involving IPA, DI water, and D-PBS was performed to see if the devices were able to differentiate between these liquids. The results showed that the fabricated Lamb wave devices exhibited sensitivity to mass loading and were able to distinguish between the liquids based on their phase, frequency, and gain characteristics. Notably, devices with the rotated design have shown a substantial increase in resonance by 15 dB, as well as enhanced sensitivity, when compared to the devices with the normal design. Furthermore, the devices featuring the normal design had a Q factor of 450, whereas devices with the rotated design exhibited a Q factor of 680, indicating superior performance of the latter. These findings suggest that a Lamb wave device with the 45° rotated IDT design holds considerable potential for liquid sensing, particularly in biomedical applications.

Acoustics has high variety of applications ranging from structural-health monitoring, sonar, and biological applications to sensors. The acoustic domain employs pressure waves for detection and provides better performance for sensing applications that require interactions with mechanical signals. High-performance sensing is possible by using acoustic biosensors in biological applications since most of the biological signals are in mechanical domain, in which the sensing mechanism directly interacts with them. In this chapter, the physics for different acoustic modes are introduced and their specific applications are mentioned, as well as sensing principles and operating mechanisms are presented. Also, the structural perspectives for acoustic biosensors are given and the fabrication techniques and materials are described. In this chapter, the biochemical principles behind the sensing are introduced and the layers and surfaces interacting with biomolecules are discussed. Some of the commercially available acoustic biosensors are presented and a short discussion of future perspectives is given.

We developed a microchip device using surface acoustic waves (SAW) and sharp-edge glass microparticles to rapidly lyse low-level cell samples. This microchip features a 13-finger pair interdigital transducer (IDT) with a 30-degree focused angle, creating high-intensity acoustic beams converging 6 mm away at a 16 MHz frequency. Cell lysis is achieved through centrifugal forces acting on Candida albicans cells and glass particles within the focal area. To optimize this SAW-induced streaming, we conducted 42 pilot experiments, varying electrical power, droplet volume, glass particle size, concentration, and lysis time, resulting in optimal conditions: an electrical signal of 2.5 W, a 20 μL sample volume, glass particle size below 10 μm, concentration of 0.2 μg, and a 5-min lysis period. We successfully amplified DNA target fragments directly from the lysate, demonstrating an efficient microchip-based cell lysis method. When combined with an isothermal amplification technique, this technology holds promise for rapid point-of-care (POC) applications.