Dissertation Title: Optical-Resolution Photoacoustic Microscopy for Probing Photo-Induced Material Properties and Dynamics at the Microscale
Date: 2026/05/26 – 2026/05/26
Dissertation Title: Optical-Resolution Photoacoustic Microscopy for Probing Photo-Induced Material Properties and Dynamics at the Microscale
Speaker: Taiyu Su, Ph.D. candidate at SJTU Global College
Time: May 26 from 2:00 p.m., 2026 (Beijing Time)
Location: Room 414A, Longbin Building
Abstract
Accurate probing of photo-induced material properties and their underlying dynamics at the microscale is of paramount importance for advancing materials science and biochemical sensing. However, existing characterization techniques often suffer from limited spatial resolution—or in some cases lack spatially resolved information altogether—or rely on exogenous labeling, which may introduce measurement complexity or perturb the system under study. Optical-resolution photoacoustic microscopy (OR-PAM), distinguished by its high spatial resolution, strong optical ab-sorption contrast, and label-free capability, as well as its sensitivity to variations in physical proper-ties, has emerged as a powerful tool for microscale characterization.
In this dissertation, OR-PAM is employed to investigate photo-induced material properties and dynamic processes at the microscale, with a focus on three representative phenomena: localized sur-face wettability modulation, photothermal dynamics in plasmonic nanofilms, and the kinetics of photo-induced phase transitions.
For the characterization of surface wettability, a mask-free laser writing technique was developed to achieve spatially controllable wettability on 1-octene passivated PSi substrates. OR-PAM was utilized to visualize wettability modifications through acoustic contrast arising from water infiltration, enabling clear identification of localized transitions from hydrophobic to hydrophilic states. The practical applicability of this patterned platform was further demonstrated through preliminary implementations in protein detection assays and open-surface microfluidic systems.
To investigate photothermal dynamics, a spatiotemporal four-dimensional (4D) photoacoustic thermometry approach was developed. Thermal fields induced by continuous-wave laser heating on plasmonic titanium nitride (TiN) nanofilms were quantitatively mapped. By integrating photoacoustic signal amplitude and acoustic time-shift measurements with a heat diffusion model, both surface and volumetric temperature distributions were reconstructed, enabling real-time tracking of heat accumulation and dissipation processes with millisecond-scale temporal resolution.
Furthermore, the dual-parameter OR-PAM framework was extended to monitor the curing kinetics of ultraviolet (UV)-curable adhesives. The results demonstrate that acoustic time shifts serve as a robust indicator of the degree of solidification, effectively overcoming the limitations imposed by strong optical scattering at solid–liquid interfaces.
In summary, this work establishes a multiparametric OR-PAM framework capable of simultaneously characterizing morphological changes, thermodynamic processes, and phase transition dynamics. It is anticipated that these findings will provide valuable methodological insights for future research in materials science, bioengineering, and advanced manufacturing.
Biography
Taiyu Su, a doctoral candidate at the Global College, Shanghai Jiao Tong University, completed both his undergraduate and doctoral studies at the same institution under the supervision of Prof. Sung-Liang Chen. His research primarily focuses on photoacoustic imaging.