Two-dimensional materials-based piezophotonic composites for tailor-made ultrasounds stimulation in biological systems (2D-UltraS)

Light-to-sound has created new opportunities for integrating miniaturized photoacoustic (PA) devices and developing minimally invasive tools with high spatial precision in life science. The PA process is based on an extremely fast thermoelastic effect, which mainly depends on the absorbed laser fluence and the material's thermal expansion coefficient. An important requirement for an efficient PA conversion is that the optical heating must be faster than the thermal expansion and heat diffusion. In this project, we propose to extend the research in photoacoustic material and devices to a new class of emerging 2D layered materials beyond graphene, called transition metal dichalcogenides (TMDCs) which will be used to develop novel piezophotonic composites with precise control of the geometry, optical and mechanical proprieties, and photoacoustic response. In this composite, the 2D-filler and decorated-2D with metal nanoparticles (NPs) are dispersed in the polymer matrix. The most studied TMDCs is MoS2, a semiconductor whose electronic gap is ~2.3 eV direct in the monolayer limit. Compare with graphene which absorbs 2% of the light, the monolayer MoS2 has strong excitonic absorption cross sections of about 10% of the incident light. This exceptional light-matter interaction, an ultrafast photocarrier, and its biocompatibility suggest that this material is a natural 2D candidate in photoacoustic giving more degrees of freedom in the realization of piezophotonic composite and opening new perspectives in this field. The PA response of these samples will be experimentally investigated in the ns and ps excitation regime for different 2D-materials (MoS2, WS2, graphene), layers ’number, metal NPs decoration, polymer chains, and film thickness. The experimental part will be supported by the theory in a multiscale approach to optimize the design of the PA emitter and unveil the interplay in the PA response between the electronic, optical, and thermal properties. Compared with graphene the use of TMDCs and nanoparticle decoration is expected to increase the photoacoustic conversion efficiency enabling the production of thinner emitters. We aim to elucidate the photoacoustic behavior of TMDCs-based composite, which will enrich the physics beyond the state-of-the-art and bring a new tile in photoacoustic devices. Successively, we will implement high spatial precision piezophotonic tools, which we are aiming to use in novel biomedical applications. Indeed, depending on the intensity and shape of the PA waveform, the areas to explore regard: i) PA waves with high spatial precision used to modulate and enhance the emission intensity of an intracellular microlaser, ii) PA wave used as a propellent agent to manipulate bioink or cell embedded in bioink, realizing a clean PA-printing, iii) in-vitro investigation on the effect of high-frequency PA wave on β-amyloid plaques, involved in Azarmehr’s disease. The proposed goals will enable new technologies with translational perspectives toward biotech factories and a clinic of the future, and further interdisciplinary research on minimally invasive US tools based on 2D materials in the biomedical field. To reach these objectives, a combination of complementary research expertise is very important. At the Faculty of Mechanical Engineering, the activities of the principal investigator and coordinator of the project Daniele Vella (Laboratory for Laser Techniques) with experience in photoacoustic, 2D material, spectroscopy, and ultrafast laser will be combined with activities of the groups at Josef Stefan Institute with expertise in synthesis and characterization of nanomaterials, integrated biophotonics. Besides this, foreign collaborating groups with expertise in photochemistry, biochemistry, and atomistic simulation will be involved.