Nuestros investigadores

Isabel Ayerdi Olaizola

Publicaciones científicas más recientes (desde 2010)

Autores: Fuentes, M.D.C, (Autor de correspondencia); Pérez, N; Ayerdi, Isabel;
Revista: THIN SOLID FILMS
ISSN 0040-6090  Vol. 636  2017  págs. 438 - 445
Microfabrication technology in the biomedical field has provided microelectrode arrays for neural implants with new development opportunities. The need for more complex physiological functions and miniaturization, as well as the use of new materials for more flexible electrodes, can now be satisfied. PDMS (Polydimethylsiloxane) substrates are elastic, biocompatible and permeable to oxygen, in addition to being a highly stable material. However, the implementation of microfabrication techniques such as deposition and patterning processes on these new substrates is not straightforward. This paper will describe the development of a reliable method to metalize thin film microelectrodes on a highly flexible medical grade PDMS layer that is suitable for long-term implantation. Platinum (Pt) microelectrodes were deposited by physical vapor deposition and pattern transfer by lift-off was chosen. Standard photolithography was used to pattern a conventional positive photoresist and was optimized to improve adhesion and to avoid cracks in the resist. The electrical behavior of the metal-polymer interface was analyzed using multiplexed DC measurements. The resistance values of seven samples and a control were acquired sequentially. Special attention was paid to the connectorization from the flexible microelectrodes to a rigid substrate. Measurements were carried out in an air-protected environment as well as in a biological environment designed to mimic the environment of the human body. Long-term stability of the Pt-PDMS interface was strongly influenced by the electrode configuration and its connection. A characteristic electrical behavior was observed for a straight-electrode configuration. This configuration demonstrated significant drift of resistance values of more than 4% during the initial 56 h. By contrast, a stable behavior was observed for a loop electrode design, with only small variations of less than +/- 0.5% caused by thermal fluctuations. (C) 2017 Elsevier B.V. All rights reserved.
Autores: Parellada-Monreal, L., (Autor de correspondencia); Martínez, Miguel; et al.
Revista: PROCEEDINGS OF SPIE, THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING
ISSN 0277-786X  Vol. 10246  2017 
ZnO thin film on alumina has been deposited by RF sputtering and processed by two dimensional direct laser interference patterning (DLIP) using a nanosecond laser (lambda=355nm). The thermodynamic and structural properties have been investigated. Morphological characterization has shown a line-pattern structure with small alterations depending on the fluence of the laser (85 mJ/cm(2) or 165 mJ/cm(2)). In order to understand these modifications, a simulation has been carried out to model the transient temperature during the DLIP to study the temperature reached by the ZnO surface for the different fluences. Moreover, a comparison with a non-interference energy distribution pulse is also simulated to corroborate the model. For samples processed by DLIP, a thermal annealing effect has been noticed when temperatures at the surface are between 1000K and 1800K. Due to the slow cooling process, a possible recrystallization of the material similar to a thermal treatment is obtained. For temperatures close or higher than 1800K, the material starts to ablate.
Autores: Pérez, N; Tavera, T.; Ellman, M.; et al.
Revista: APPLIED SURFACE SCIENCE
ISSN 0169-4332  Vol. 258  Nº 23  2012  págs. 9370-9373
This work presents the fabrication of hollow-core metallic structures with a complete laser interference lithography (LIL) process. A negative photoresist is used as sacrificial layer. It is exposed to the pattern resulting from the interference of two laser beams, which produces a structure of photoresist lines with a period of 600 nm. After development of the resist, platinum is deposited on the samples by DC sputtering and the resist is removed with acetone. The resulting metallic structures consist in a continuous platinum film that replicates the photoresist relief with a hollow core. The cross section of the channels is up to 0.1 mu m(2). The fabricated samples are characterized by FESEM and FIB. This last tool helps to provide a clear picture of the shape and size of the channels. Conveniently dimensioned, this array of metallic submicrometric channels can be used in microfluidic or IC cooling applications. (c) 2012 Elsevier B.V. All rights reserved.
Autores: Manrique, Raquel; Picciaffuoco, S.; Gracia, Javier; et al.
Revista: International Journal of Pediatric Otorhinolaryngology
ISSN 0165-5876  Vol. 75  Nº Supl. 1  2011  págs. 85