Projects
One of the most common causes of abnormalities in our skin relates to structural changes in the internal constituents that exhibit subtle and undetectable physical changes to the clinical eye. The clinical tools available for skin inspection and examination are insufficient to evaluate these microscopic changes. This research project introduces a non-invasive, compact and capable solution to overcome these difficulties using an acoustic imaging technique for a continuous observation of the subtle changes of the skin lesions. We investigate laser-induced photoacoustic methods to probe the skin layers and some of their most notable structures, such as the hair follicle. The methods used take advantage of the generation of wideband pulses with very high frequencies, beyond 100 MHz, to investigate these structures with greater accuracy. The generation of such broadband ultrasonic pulses will be made with innovative piezophotonic materials capable of efficiently converting the energy of a pulse of infrared light (e.g., 30 mJ at 1064 nm) into broadband ultrasound. The skin is composed of layers of corneocytes with submillimetric thicknesses that constitute an effective barrier against allergens, toxins and many chemicals, including the permeation of drugs. At ultrasound pulses at high intensities (> 10 atm) proved to be efficient in the permeabilization of biologic membranes, such as the skin.
In an aging society, where it is predicted that the active life of the population may soon be extended to 70 years of age, there is a growing need to look young and healthy. Capillary restoration constitutes one of the main concerns and it’s among the most common surgical procedures of aesthetic and regenerative medicine. In 2006, 5% minoxidil had been approved by the FDA for topical treatment of alopecia without a prescription. Additionally, the use of minoxidil is recommended concomitantly or after hair transplantation. Although the use of minoxidil proved its efficacy in alopecia treatment, the prescribed twice a day topical treatment leads to low compliance and overall discouraging results. This investigation propose the integration into a miniaturized device, with low cost of production, the following characteristics: (i) echography with very high frequency ultrasound, (ii) infrared photoacoustics and (iii) permeabilization of the skin. The evaluation of the potential of this device ought to be made in real environment, collecting information about the hair follicle, and its potential to permeabilize the skin and increase the delivery of minoxidil to the hair follicle, in order to combat the decrease of its volume and remedy alopecia.
Photoacoustic waves are generated when pulsed light, eg. a laser pulse strikes an absorptive material, transforming this energy into heat that is rapidly dissipated (picoseconds). This rapid deposition of heat generates a high-frequency acoustic wave, or pressure wave, that will propagate through the material. The frequency and wavelength associated with this pressure wave depend on the elastic properties of the material, which is intrinsically related to the speed of sound in the material. If the characteristics of the incident light pulse are modulated according to the frequency of the photoacoustic wave generated in the material, it is possible to obtain the resonance condition between the frequency of the photoacoustic wave (pressure wave) generated and the incidence frequency of the laser beam pulse, which will produce a new wave at each incidence, thus generating a resonant pressure wave.
Our proposal is to use metal plates with different thicknesses, from micrometers to millimeters and produce resonant photoacoustic waves in order to generate high pressures in the structure of this metal, inducing change in the positions of the atoms in its structure. These pressure waves must reach the Hugoniot pressure limit, which determines the irreversible elastic limit of deformation of the structure of a solid with values between 0.2 to 20GPa of pressure. Upon reaching this limit, the internal structure of the metals are expected to undergo a sufficiently large deformation to promote a structural change.
It is intended from rice husk to obtain silicon oxide (and silicon) and silicon carbide, with a high degree of purity (greater than 99.8%). It is intended to develop new processes and methods minimizing the energy cost. The work starts from a laboratory scale in which it is intended to determine the influence of several variables on which the processes depend (such as composition, temperature, stoichiometry) on the efficiency of new proposed processes. It is intended to investigate the reaction mechanisms associated with the processes. The first objective will be to use more efficient pre-treatment processes, using physical and chemical methods that allow achieving high purities and morphology control. The second objective involves the use of thermal processes with magnesium in order to reduce the pyrolysis temperature from 1400-1800 °C to 500-900 °C, lowering the footprint and energy bill. In order to obtain silicon with high purity and morphological control, we will also use an alternative and innovative way of promoting the reduction of silica to silicon from a carbothermic process induced by a pulsed laser beam, a way that we intend to develop with a higher energetic efficiency for the necessary heat transfer of reaction.