Microstructuring of materials with laser technologies for biomedical applications

  1. Aymerich López, María de la Inmaculada
Dirixida por:
  1. Maria Teresa Flores-Arias Director

Universidade de defensa: Universidade de Santiago de Compostela

Fecha de defensa: 02 de xullo de 2019

  1. Carmen Bao Varela Presidenta
  2. Javier Rodríguez Vázquez de Aldana Secretario/a
  3. Jürgen Van Erps Vogal
  1. Departamento de Física Aplicada

Tipo: Tese


This thesis presents the use of laser technologies for structuring different materials for applications in biomedicine. One of the aims of this work is the fabrication of fluidic chips for their employment as preclinical devices. During the past decades there has been a growing interest in the study and development of analysis devices due to the important applications they present in different scientific fields, such as Chemistry, Biology or Medicine. Different fabrication techniques have been described for this purpose but among them, laser outstands thanks to its accuracy, versatility or speed. By direct or indirect laser techniques, materials like soda-lime glass, titanium or tantalum are structured. In this work, main ablation mechanisms are reviewed regarding the temporal duration of the laser pulse as well as the response of the material to the laser wavelength. Microchannels with similar dimensions are fabricated over soda-lime glass by laser direct ablation using three different laser systems with same wavelength, in the infrared spectral range, but pulse durations of nano, pico and femtoseconds. Results are analysed and evaluated, finding significant differences depending on the side of the glass . Thermal treatments are applied to the microchannels to modify their initial roughness. Millimetre dimension channels are obtained in soda-lime glass by indirect laser ablation with a nanosecond laser system. These structures are employed as master that replicates its structure for creating a preclinical device that imitates a coronary bifurcation. The replica procedure is known as soft-lithography and is performed in polydimethylsiloxane (PDMS), biocompatible material suitable for long term cell cultures. The device is validated with human umbilical vein endothelial cells that adhere and attach to the totality of the inner surface of the channel. Optimal roughness value of the device is determined for cells to withstand flux conditions. Degradation of PDMS to some organic solvents commonly employed in biomedicine is solved by coating the channels with sol-gel chemistry. Different compositions are employed: 60MTES/40TEOS, 70MTES/30TISP and 80MTES/20TISP. Cell behaviour is studied over the different coatings. These devices that imitate coronary bifurcations are employed to determinate low velocity areas in these blood vessels. In these zones, fluid dynamics is altered and can lead to the development of vascular pathologies. The experimental results are compared to numerical ones. Finally, other applications of laser structuring for biomedical applications are presented. Using a microlens array and the Talbot effect, biocompatible material titanium and tantalum are ablated with a pulsed laser. Thanks to the Talbot phenomenon, different patterns from the original can be achieved and damage of the microlens array during the ablation is avoided. The impact of the patterns in cellular growth is studied by culturing endothelial cells over the structured substrates. By laser indirect ablation, a microfluidic device for capturing circulating tumour cells is fabricated over soda-lime glass. The device if functionalized and validated, showing a trapping efficiency above the 75%.