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Dive into the research topics where A. T. Sepúlveda is active.

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Featured researches published by A. T. Sepúlveda.


Nanoscale | 2013

Full elastic constitutive relation of non-isotropic aligned-CNT/PDMS flexible nanocomposites

A. T. Sepúlveda; R. Guzmán de Villoria; J. C. Viana; A. J. Pontes; Brian L. Wardle; Luís A. Rocha

The elastic response of vertically aligned-carbon nanotube/polydimethylsiloxane (A-CNT/PDMS) nanocomposites is presented in this study and related to the underlying aligned-CNT morphology. Multiwalled carbon nanotubes (MWCNTs) at 1% Vf are embedded in a flexible substrate of PDMS to create a flexible polymer nanocomposite (PNC). The PNC properties are evaluated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and tensile mechanical tests, and the full linearly elastic constitutive relation is established for such a PNC. The results suggest that the CNTs retain the alignment after wetting and curing of PDMS. PDMS is significantly modified by the reinforcing aligned-CNT fibers, demonstrating non-isotropic (as opposed to the isotropic neat PDMS) elastic properties all different from PDMS (Youngs modulus of 0.8 MPa), including an anisotropy ratio of 4.8 and increases in the modulus of A-CNT/PDMS over PDMS by more than 900% and 100%, in the CNT longitudinal and transverse directions, respectively. This study reports the first full constitutive relation that may be useful in modeling PNCs as composites or as elements of hierarchical nanoengineered composites, particularly PDMS-CNT PNCs are envisioned as elements in biomedical devices such as pressure transducers and energy harvesters.


IEEE Transactions on Biomedical Engineering | 2015

Implantable Flexible Pressure Measurement System Based on Inductive Coupling

Cristina Oliveira; A. T. Sepúlveda; N Almeida; Brian L. Wardle; José Machado da Silva; Luís A. Rocha

One of the currently available treatments for aortic aneurysms is endovascular aneurysm repair (EVAR). In spite of major advances in the operating techniques, complications still occur and lifelong surveillance is recommended. In order to reduce and even eliminate the commonly used surveillance imaging exams, as well as to reduce follow-up costs, new technological solutions are being pursued. In this paper, we describe the development, including design and performance characterization, of a flexible remote pressure measurement system based on inductive-coupling for post-EVAR monitoring purposes. The telemetry system architecture and operation are described and main performance characteristics discussed. The implantable sensor details are provided and its model is presented. Simulations with the reading circuit and the sensors model were performed and compared with measurements carried out with air and a phantom as media, in order to characterize the telemetry system and validate the models. The transfer characteristic curve (pressure versus frequency) of the monitoring system was obtained with measurements performed with the sensor inside a controlled pressure vacuum chamber. Additional experimental results which proof the system functionality were obtained within a hydraulic test bench that emulates the aorta. Several innovative aspects, when compared to the state of the art, both in the sensor and in the telemetry system were achieved.


international conference of the ieee engineering in medicine and biology society | 2011

Flexible sensor for blood pressure measurement

A. T. Sepúlveda; A. J. Pontes; J. C. Viana; R. Guzmán de Villoria; Fabio Fachin; Brian L. Wardle; Luís A. Rocha

A new approach for the design and fabrication of a highly flexible blood pressure sensor is introduced in this paper. The goal is to measure the pressure within an aneurysm sac for post-endovascular aneurysms repair (EVAR) surveillance. Biocompatible polydimethylsiloxane (PDMS) membranes with embedded aligned carbon nanotubes (CNTs) are used to build the conductive elements of the pressure sensitive capacitor and the inductor for telemetry. Inductive coupling will be used to measure the internal capacitive variations. Fabricated test sensors validate the approach and demonstrate that CNTs/PDMS technology can be used to build highly flexible pressure sensors.


Technologies for medical sciences, Book Series: Lecture Notes in Computational Vision and Biomechanics | 2012

Improving Post-EVAR Surveillance with a Smart Stent-Graft

Isa C. T. Santos; A. T. Sepúlveda; J. C. Viana; A. J. Pontes; Brian L. Wardle; S. M. Sampaio; R. Roncon-Albuquerque; João Manuel R. S. Tavares; Luís A. Rocha

Abdominal aortic aneurysms (AAA or triple A’s) are indolent and deadly diseases. Their treatment options involve either an invasive procedure or a minimally invasive one. When the minimally invasive procedure, endovascular aneurysm repair (EVAR), was introduced, it revolutionized the treatment of AAA’s due to advantages such as shortened hospital stays and reduced costs. As EVAR requires periodic imaging exams, questions are nowadays being raised regarding the procedure’s long-term cost-benefit relation. In order to reduce follow-up costs, new technological solutions are being pursued, namely EVAR stent-grafts with sensing capabilities. In this chapter, the suitability of aneurysm sac pressure measurement for EVAR surveillance is evaluated using an AAA computer model. In addition the design drivers underlying EVAR stent-grafts are reviewed and the development of a new flexible pressure sensor integrated into a stent-graft is described.


international conference on biomedical electronics and devices | 2015

Carbon Nanotubes - The Challenges of the First Syntheses Trials

Cláudia Coelho; A. T. Sepúlveda; Luís A. Rocha; Alexandre Ferreira da Silva

The authors wish to thank FCT – Fundacao para a Ciencia e Tecnologia, Portugal, for the financial support provided under the project PTDC/EEIELC/1838/2012.


Procedia Engineering | 2011

Nanocomposite Flexible Pressure Sensor for Biomedical Applications

A. T. Sepúlveda; Fabio Fachin; R. Guzmán de Villoria; Brian L. Wardle; J. C. Viana; A. J. Pontes; Luís A. Rocha


Procedia Engineering | 2012

Flexible Pressure Sensors: Modeling and Experimental Characterization

A. T. Sepúlveda; R. Guzmán de Villoria; J. C. Viana; A. J. Pontes; Brian L. Wardle; Luís A. Rocha


international conference on biomedical electronics and devices | 2018

DESIGN OF A PRESSURE SENSOR FOR MONITORING OF POST-ENDOVASCULAR ANEURYSM REPAIR

A. T. Sepúlveda; A. J. Pontes; J. C. Viana; Luís A. Rocha; Isa C. T. Santos; Fabio Fachin; R. Guzmán de Villoria; Brian L. Wardle


Archive | 2011

IMPLANTABLE FLEXIBLE SENSOR BASED ON ALIGNED-CARBON NANOTUBES FOR BLOOD PRESSURE MONITORING

Escola de Engenharia; A. T. Sepúlveda; Luís A. Rocha; J. C. Viana; A. J. Pontes


MME 2010 - 21st Micromechanics and Microsystems Europe Workshop | 2010

Inductive-coupling system for abdominal aortic aneurysms monitoring based on pressure sensing

A. T. Sepúlveda; A. Moreira; Fabio Fachin; Brian L. Wardle; J. M. Silva; A. J. Pontes; J. C. Viana; Luís A. Rocha

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Brian L. Wardle

Pennsylvania State University

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R. Guzmán de Villoria

Massachusetts Institute of Technology

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Fabio Fachin

Massachusetts Institute of Technology

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