Speaker
Description
The ability to finely tune and probe the elastic properties of microstructured materials is central to the design of advanced phononic, optomechanical, and bio-inspired systems. Silica microparticles synthesized via the Stöber process are widely used as model resonators and building blocks for phononic materials; however, their stiffness is typically determined by the synthesis conditions and remains fixed thereafter. Here, we demonstrate that moderate electron-beam irradiation, originally intended to charge silica micro-electrets [1], can be leveraged to engineer their elastic moduli [2]. This creates tunable hypersonic resonators where the charge state and mechanical response are simultaneously controlled.
This electromechanical coupling introduces new channels for interaction with external stimuli. As a proof of concept, we demonstrate energy transfer by coupling an RF electromagnetic field with the acoustic modes of the particles, suggesting potential applications in miniaturized RF antennas and mechano-chemical sensors. Beyond technological advancements, this approach underscores the efficacy of Brillouin spectroscopy in probing mechanical properties at the single-microparticle level. It establishes a robust methodology for investigating how local structural modifications, charge, and environmental factors influence elasticity at the microscale. This method is particularly relevant for biological and soft matter, where hydration, ionic environment, and molecular organization dictate mechanical behavior [3]. Consequently, irradiated silica particles serve as an ideal benchmark for interpreting Brillouin Light Scattering (BLS) measurements of viscoelastic properties in complex systems.
References:
[1] Bonacci, F., Di Michele, A., Caponi, S., Cottone, F., & Mattarelli, M. (2018). High charge density silica micro-electrets fabricated by electron beam. Smart Materials and Structures, 27(7), 075052.
[2] Bonacci, F., Cottone, F., Di Michele, A., Passeri, A. A., Madami, M., Caponi, S., & Mattarelli, M. (2025). Tunable Hypersonic Resonators via Electron‐Irradiation‐Induced Giant Modulation of Microparticle Elasticity. Small, 21(18), 2410278.
[3] Passeri, A. A., Morena, F., Argentati, C., Bonacci, F., Neri, I., Fioretto, D., ... & Caponi, S. (2025). Beyond Water Content: Unraveling Stiffness in Hydrated Materials by a Correlative Brillouin–Raman Approach. ACS photonics, 12(7), 3794-3802.