María Aymerich

A laser-based technology for fabricating a soda-lime glass based microfluidic device for circulating tumour cell capture

We developed a laser-based technique for fabricating microfluidic microchips on soda-lime glass substrates. The proposed methodology combines a laser direct writing, as a manufacturing tool for the fabrication of the microfluidics structures, followed by a post-thermal treatment with a CO2 laser. This treatment will allow reshaping and improving the morphological (roughness) and optical qualities (transparency) of the generated microfluidics structures. The use of lasers commonly implemented for material processing makes this technique highly competitive when compared with other glass microstructuring approaches. The manufactured chips were tested with tumour cells (Hec 1A) after being functionalized with an epithelial cell adhesion molecule (EpCAM) antibody coating. Cells were successfully arrested on the pillars after being flown through the device giving our technology a translational application in the field of cancer research.

Laser-based surface multistructuring using optical elements and the Talbot effect.

We present a laser based technique combined with the Talbot effect for microstructuring surfaces. The use of the Talbot effect is introduced as a solution to avoid damage of the periodic object used for micropattering different surfaces during the ablation process. The fabrication of two periodic objects (a mask and a microlens array) for micropattering surfaces and the identification of their Talbot planes is presented. A metal foil is ablated at distances corresponding to selected Talbot planes of the periodic objects. The setup allows us to design the desired pattern and the result is a multistructured surface with a high number of identical microholes, achieving a minimum diameter around 4μm. The different aspect of the periodic object working in direct contact and working at these Talbot distances is shown. These pictures reveal the advantages of working of using Talbot effect for a rapid, repeatable and no-contaminant multistructuring. Some industrial applications are illustrated.

Study of Different Sol-Gel Coatings to Enhance the Lifetime of PDMS Devices: Evaluation of Their Biocompatibility

A study of PDMS (polydimethylsiloxane) sol-gel–coated channels fabricated using soft lithography and a laser direct writing technique is presented. PDMS is a biocompatible material that presents a high versatility to reproduce several structures. It is widely employed in the fabrication of preclinical devices due to its advantages but it presents a rapid chemical deterioration to organic solvents. The use of sol-gel layers to cover the PDMS overcomes this problem since it provides the robustness of glass for the structures made with PDMS, decreasing its deterioration and changing the biocompatibility of the surface. In this work, PDMS channels are coated with three different kinds of sol-gel compositions (60MTES/40TEOS, 70MTES/30TISP and 80MTES/20TISP). The endothelial cell adhesion to the different coated devices is evaluated in order to determine the most suitable sol-gel preparation conditions to enhance cellular adhesion.

Laser Surface Microstructuring of Biocompatible Materials Using a Microlens Array and the Talbot Effect: Evaluation of the Cell Adhesion

A laser based technique for microstructuring titanium and tantalum substrates using the Talbot effect and an array of microlenses is presented. By using this hybrid technique; we are able to generate different patterns and geometries on the top surfaces of the biomaterials. The Talbot effect allows us to rapidly make microstructuring, solving the common problems of using microlenses for multipatterning; where the material expelled during the ablation of biomaterials damages the microlens. The Talbot effect permits us to increase the working distance and reduce the period of the patterns. We also demonstrate that the geometries and patterns act as anchor points for cells; affecting the cell adhesion to the metallic substrates and guiding how they spread over the material.

Laser technique for the fabrication of blood vessels-like models for preclinical studies of pathologies under flow conditions

In this work a method for fabricating functionalized preclinical devices is presented. The manufacturing process combines a laser indirect writing technique to fabricate a soda-lime glass master and soft-lithography methods to obtain the final structure in polydimethylsiloxane (PDMS). The roughness of the device is modified in a controlled manner by applying a post-thermal treatment to the master, and thus devices with different roughness values are created. The PDMS devices are fully covered with human umbilical vein cells in a two-step process. In order to determine the most suitable device to perform bioassays, the cell attachment to the channel is evaluated with regards to the walls roughness when flow experiments are carried out.

Determination of hemodynamic risk for vascular disease in planar artery bifurcations

Understanding hemodynamics in blood circulation is crucial in order to unveil the mechanisms underlying the formation of stenosis and atherosclerosis. In fact, there are experimental evidences pointing out to the existence of some given vessel configurations that are more likely to develop the above mentioned pathologies. Along this manuscript, we performed an exhaustive investigation in a simplified model aiming to characterize by means of physical quantities those regions and configurations in vessel bifurcations that are more likely to develop such pathologies. The two-fold analysis is based, on the one hand, on numerical simulations (via CFD) and, on the other hand, on experiments realized in an ad-hoc designed polydimethylsiloxane (PDMS) channel with the appropriate parameters and appropriate fluid flows. The results obtained demonstrate that low velocity regions and low shear stress zones are located in the outer walls of bifurcations. In fact, we found that there is a critical range of bifurcation angles that is more likely to vascular disease than the others in correspondence with some experimental evidence. The effect of the inflow velocity on this critical range is also analyzed.

Laser based fabrication of preclinical devices for fluidic experiments

Since some pathologies, such as cardiovascular or tumour diseases, have become some of the main causes of morbidity worldwide, a huge interest in the development of preclinical devices for their study has aroused during the past years. Their fabrication is a key factor for the study of these illnesses and it is directly linked with their pathological knowledge, early diagnosis and improvement of treatment.

Laser surface multistructuring of biocompatible materials using a microlens array and the Talbot effect

It has been demonstrated that cell adhesion on biocompatible materials is modified when the surface of the material is structured instead of being totally polished [1-3]. An efficient way to texture surfaces is using the foci of a microlens array and a direct write laser technique [4]. Due to the short focal length of the microlens, they can be damaged by expelled material during ablation. In previous works we have demonstrated the capability of using the Talbot effect to distance the object from the substrate to structure it, avoiding the damage of the microlens [5]. The Talbot effect consists of the repetition of the image of a periodic object, such as the foci of microlens, when it is illuminated by a coherent beam [6]. In this work, also the fractional Talbot effect will be employed to obtain the same pattern of ablation but with a reduced period [7].

The USC-OSA-EPS section activities in optics

The USC-OSA Student Chapter and USC-EPS Young Minds Section is a group financed by The Optical Society (OSA) and the European Physical Society (EPS). It is formed by PhD and degree students from the Universidade de Santiago de Compostela (USC) and one supervisor of the Faculty of Physics. Its main goal is to promote and diffuse Optics in the society. For this purpose, the group carries out several activities in the academic and non-academic community. The group is also committed to the professional development of our members and motivates the exposition of our work into the scientific community.

Laser based manufacturing of channels and improvement of their lifetime with sol-gel coatings

A preclinical device that mimics half blood vessel by using laser technologies has been developed. By employing a Nd:YVO4 laser a channel has been manufactured over soda-lime glass. Using a CO2 laser combined with a roller furnace, a thermal treatment has been applied to the channel to enhance its quality. The glass structure was employed as master to replicate the channel in PDMS by soft-lithography. To avoid the deterioration of the PDMS, channels were coated with three different sol-gel coatings compositions. Endothelial cells were cultured over the channels to determine the most suitable surface for cell growing.