67 documents found, page 1 of 7
Magnesium fluoride as low-refractive index material for near-ultraviolet filter...
Silva, Manuel Fernando Ribeiro; Pimenta, Sara Filomena Ribeiro; Rodrigues, José Artur Oliveira; Freitas, João Rui Martins; Ghaderi, M.; Gonçalves, L. M.This article describes the fabrication of MgF2 and MgO thin-film-based optical filters and compares the optical transmission of the filters over UV. The MgF2 thin-films were deposited by use of an e-beam technique and their optical properties were characterised by ellipsometry. The effect of substrate temperature on the optical properties was studied. The MgF2 optimum refractive indices were obtained with a sub...
Photodynamic therapy at low-light fluence rate: "in vitro" assays on colon canc...
Rodrigues, J. A.; Amorim, Ricardo; Silva, M. F.; Baltazar, Fátima; Wolffenbuttel, R. F.; Correia, J. H.This paper presents the results of in vitro photodynamic therapy assays on RKO and HCT-15 cell lines. The envisaged implementation is in autonomous medical microdevices, such as endoscopic capsules for clinical treatment of several types of gastrointestinal tract tumors. Because of their very limited device volume, light fluence and fluence rate needed to destroy tumor cells should be minimized. Foscan or meta-...
A 45° saw-dicing process applied to a glass substrate for wafer-level optical s...
Maciel, M. J.; Costa, C. G.; Silva, M. F.; Gonçalves, S. B.; Peixoto, A. C.; Ribeiro, A. Fernando; Wolffenbuttel, R. F.; Correia, J. H.This paper reports on the development of a technology for the wafer-level fabrication of an optical Michelson interferometer, which is an essential component in a micro optoelectromechanical system (MOEMS) for a miniaturized optical coherence tomography (OCT) system. The MOEMS consists on a titanium dioxide/silicon dioxide dielectric beam splitter and chromium/gold micro-mirrors. These optical components are de...
A wafer-level miniaturized Michelson interferometer on glass substrate for opti...
Maciel, Marino Jesus Correia; Costa, C. G.; Silva, Manuel Fernando Ribeiro; Peixoto, Alexandre Coumiotis Moreira; Wolffenbuttel, R. F.; Correia, J. H.The wafer-level fabrication of a Michelson interferometer using optical MEMS technologies is presented. The intended application is in Optical Coherence Tomography (OCT). The micro fabrication involves two steps: the 45 saw dicing of glass substrate and the subsequent deposition of a dielectric multilayer and metallic layers to obtain a beam splitter and waveguide micro mirrors, respectively. The Michelson inte...
NIR micro beam-splitter by saw-dicing of glass substrate for Optical Coherence ...
Maciel, Marino Jesus Correia; Costa, C. G.; Peixoto, Alexandre Coumiotis Moreira; Wolffenbuttel, R. F.; Correia, J. H.This paper reports the fabrication of a near infrared (NIR) micro beam-splitter (MBS) for Optical Coherence Tomography (OCT) applications. The proposed configuration is based on saw-dicing micromachining of glass substrate combined with thin film deposition of a dielectric multilayer. In order to obtain a splitting with horizontal and vertical transmitted/reflected beams, a 45° surface was fabricated with conve...
Optical filter for providing the required illumination to enable narrow band im...
Silva, Manuel Fernando Ribeiro; Rodrigues, José Artur Oliveira; Oliveira, Maria J.; Fernandes, A. R.; Pereira, S.; Costa, C. G.; Ghaderi, M.This paper presents the design, fabrication and characterization of two Fabry Perot type optical filters (415 nm and 540 nm) for enabling Narrow Band Imaging (NBI) in medical devices (MD). The two-colour illumination should satisfy a highly specific optical design, which is composed of a thin-film optical filter stack of titanium dioxide (TiO2 ) and silicon dioxide (SiO2 ) thin-films and commercially available ...
Gas viscosity mems sensor based on pull-in
Dias, R. A.; Graaf, G. de; Wolffenbuttel, R. F.; Rocha, L. A.A novel method for measuring the viscosity of gases is introduced here, that uses a parallel-plate capacitive device, electrostatically actuated to pull-in. In welldefined actuation and damping conditions, the pull-in time is proportional to viscosity of the gas medium between the plates, since viscosity determines the damping level. MEMS structures have been fabricated to experimentally verify the method of us...
Closed loop operation of time-based accelerometers
Dias, Rosana A.; Wolffenbuttel, R. F.; Cretu, E.; Rocha, Luís A.In this paper we present a method for closed-loop operation of pull-in time accelerometers. Accelerometers based on the measurement of the pull-in time of movable parallel-plates MEMS structures have already demonstrated very good resolution capabilities, with low requirements on the capacitive readout. However, open-loop operation delivers very low dynamic range and highly non-linear response. The closed-loop ...
Closed-loop operated time-based accelerometer
Dias, Rosana A.; Macedo, Pedro; Silva, Hélder D.; Wolffenbuttel, R. F.; Cretu, E.; Rocha, Luís A.A high-resolution, high dynamic range capacitive accelerometer based on pull-in time measurement is described in this paper. The high sensitivity of pull-in time can be used to implement high performance accelerometers, but non-linearity and low dynamic range compromise device performance. A closed-loop approach using an electrostatic actuation mechanism to control the duration of the pull-in time is presented,...
A review of visible-range Fabry–Perot microspectrometers in silicon for the ind...
Carmo, João Paulo Pereira; Rocha, R. P.; Correia, J. H.; Graaf, G. de; Bartek, Marian; Wolffenbuttel, R. F.This review presents microspectrometers in silicon for the industry for measuring light in the visible range, using the Fabry–Perot interferometric technique. The microspectrometers are devices able to do the analysis of the individual spectral components in a given signal and are extensively used on spectroscopy. The analysis of the interaction between the matter and the radiated energy can found huge applicat...