Surface Cleaning of SAW-Based Microparticle Sensors Integrated in a Cascade Impactor Using SAW-Induced Droplet Displacement

Investigation of Atomization-Based Water Removal Mechanism Utilizing Piezoelectric Ceramic-Glass Substrate Coupling Dynamics

Photo-Triggered Directional Movement of a Water Droplet on Surfaces by Liquid Crystal Elastomers

The precise control of droplet movement on surfaces remains a major challenge in the field of smart surfaces. Conventional systems based on light, electric, or magnetic stimuli often require the addition of corresponding photothermal, conductive, or magnetic particles into the droplets, which may lead to droplet contamination and hinder encapsulation of drugs or cells for practical application. In the present study, a photo-responsive composite functional surface was designed and prepared. The functional surface contains a liquid crystal elastomer (LCE) layer which is placed underneath a pre-lubricated polydimethylsiloxane surface. Taking advantage of the photo-induced thermal response of the cross-linked LCE network, upon local irradiation with ultraviolet light, the illuminated region of the LCE layer rapidly generates dynamic heating, creating a temperature gradient across the droplet. This gradient alters the surface tension of the solid surface, disrupts the symmetry of contact angles of the droplet, thereby inducing directional droplet movement along the surfaces. The present study provides a non-contact and fast approach for the fabrication of smart surfaces towards more complex droplet manipulation.

Parametric Analysis of SAW-Driven Droplet Streaming for Biomedical Lab-on-Chip Systems

Surface acoustic wave (SAW)–induced acoustic streaming has emerged as a powerful mechanism for manipulating microscale fluids in droplet-based microfluidic systems, with promising applications in biomedical diagnostics and bioelectronic lab-on-chip platforms. This study presents a numerical investigation of acoustic streaming in sessile droplets driven by SAWs, with a focus on understanding the influence of key physical parameters on flow behavior and mixing performance. A three-dimensional multiphysics model was developed to simulate the coupling between surface acoustic wave excitation, acoustic pressure fields, and induced fluid flow within a droplet. Parametric analyses were conducted by varying the SAW excitation frequency and droplet size to evaluate their effects on streaming velocity and mixing efficiency. The results reveal that both parameters significantly affect the formation of vortex structures and the intensity of internal recirculation within the droplet. Lower excitation frequencies generally lead to stronger acoustic streaming, while droplet size influences the spatial distribution of flow patterns. These findings provide insights into the design and optimization of SAW-driven microfluidic platforms for efficient biological sample manipulation and rapid mixing in biomedical sensing and diagnostic applications.

Non-Contact Evaluation of Film Electroadhesion using Laser Ultrasonics and SAWs

Film adhesion is a critical phenomenon that has been thoroughly investigated to improve structural reliability, notably in microelectronics. In this work, Laser Ultrasonics is used to evaluate the bond quality achieved by an original electroadhesion process. More precisely, an electrostatic field is applied to a polyvinyl chloride film deposited on an aluminum substrate, thereby eliminating the need for an adhesive layer. The effects of electroadhesion on Surface Acoustic Waves (SAWs) are explored, with results solely attributable to interfacial adhesion changes. These waves are generated in thermoelastic regime by a frequency-doubled Nd:YAG pulsed laser and detected by a Mach-Zehnder heterodyne interferometer. The experimental Rayleigh mode dispersion curves are compared to the theoretical ones, facilitating adhesion evaluation through inverse problems. Furthermore, Finite Element Modeling predicts acoustic wave propagation in the structure, enabling experimental and numerical comparisons. This research paves the way for a multiphysical analysis of electrostatic field-induced coating adhesion.

Research on auxiliary coating techniques for nanosecond laser processing of glass surfaces

Water Droplet Hammer: Piezoelectric Sensing of Ultrafast Mechanical Transients During Droplet Impact.

Erosion and fracture caused by repeated water-droplet impacts are often attributed to splash-mediated material removal, high-pressure impulsive loading, or cavitation. Yet, the mechanical response during the earliest instant of impact remains difficult to capture. Using a high-temporal-resolution polyvinylidene fluoride (PVDF) piezoelectric sensor combined with high-speed imaging, we directly measure substrate-coupled mechanical transients during a single water-droplet impact. A strong impulsive strain response appears within the first 2 ms after contact, followed by coherent 100-500 Hz oscillations at the water-solid interface during the first 20 ms, before any rebound occurs. The oscillation frequency is modulated by an effective interfacial stiffness, whereas the impulsive peak-to-peak response scales with droplet size and impact velocity. The experimentally captured signals provide direct experimental evidence of ultrafast substrate-coupled mechanical transients during droplet impact and establish a minimal inertial-capillary framework for understanding mechanical signatures that may contribute to low- to moderate-speed droplet-induced erosion and fatigue.