The aim of this work is to improve the understanding of the interaction between photoacoustic waves and skin. We
employ photoacoustic waves with 1 MPa amplitude and center frequencies of 100 MHz to transiently perturb model lipid
membranes and the stratum corneum of mini pigs. The lipid structure transient perturbation observed is tentatively
attributed to a temperature rise mechanism. We also try to show that the dynamic acoustic radiation force mechanism can
explain the perturbation induced by photoacoustic waves in skin. Indeed, 15 bar pressure gradients across 5 corneocytes
(approx. 5 μm wide) are shown to transiently perturb the skin structure.
Pressure waves generated by laser pulses can permeabilize biological barriers, such as the skin or cellular membranes.
The characteristics of the absorbing materials are decisive in determining the shape and amplitude of pressure impulse
transients. Based on the physics and photochemistry of light-to-pressure conversion, we generate high intensity
broadband ultrasound capable of transiently permeabilizing biological barriers. We show evidence that no damage is
done to cells exposed to such pressure waves and that skin recovers its protective function some minutes after exposure
to the pressure waves. The ability of the pressure waves to promote transient skin permeabilization is assessed by the
increase of transepidermal water loss (TEWL) immediately after the application of pressure waves, and by the full
recovery of the skin to the normal TEWL values in the following minutes.
A skin depth map was built reconstructing photoacoustic signals at several wavelengths of visible and infrared light.
The mapping technique was used to follow the diffusion through the skin of near-infrared absorbing dyes. Such dyes
can be useful for photodynamic therapy (PDT) of skin lesions and are investigated as contrast agents for
photoacoustic tomography (PAT), because they strongly absorb light at wavelengths where the skin is more