Slot antenna design for a wirelessly powered implantable microcooler for neuronal applications

Implantable medical devices are becoming smaller by the day, with more efficient electronics and smaller power demands. Nevertheless, there are some applications in which power demands are inherently high, and solutions must be found in order to keep the devices as small as possible. In this paper, we propose an antenna to be used in wirelessly powering a focal brain cooling implant based on a Peltier device. This antenna is designed in order to act as a heatsink for the device with the goal of minimizing its final volume, therefore design constrains such as size limitations and geometry restrictions are considered.This work is supported by FCT with the reference project PTDC/EEI-TEL/5250/2014, by FEDER funds through Projecto 3599 - Promover a Producao Cientifica e Desenvolvimento Tecnologico e a Constituicao de Redes Tematicas (3599-PPCDT).info:eu-repo/semantics/publishedVersio

Characterization of chip-size electrically-small antennas for smart wireless biomedical devices

The new requirements for smarter and smaller biomedical microsystems demand for new integration technologies, including antenna integration. This can be solved with the use of microfabrication technologies, allowing the fabrication of chip-size antennas that may be placed on top of silicon wafers. However, due to their ultra-small physical dimensions and special operating conditions (e.g., covered with body tissue phantoms), antenna characterization requires the use of auxiliary custom-made transitions between antenna and test equipment, which are much larger than the antennas under test. Since electrically small antennas show also very small gain, the use of test boards may carry a significant impact on the antenna's characteristics. This paper presents a methodology used to investigate the performance of chip-size 3D antennas (500x500x500 mu m(3)) designed to operate inside the human body in the frequency band 1-8 GHz.This work was supported by Portuguese Foundation for Science and Technology: FCT-PTDC/EEI-TEL/2881/2012, Programa Operacional Temático Fatores de Competitividade (COMPETE) and Fundo Comunitário Europeu FEDER.info:eu-repo/semantics/publishedVersio

Performance assessment of wireless power transfer links for implantable microsystems

Wireless power transfer is a hot topic due to the growth of implanted device solutions which, as they get smaller and smarter, demand new solutions to power them up. These solutions need to keep the power level, namely SAR (specific absorption ratio) below a determined safety standard and to allow the device to be as small as possible. Current fabrication techniques allow the creation of ultra-small 3D antennas integrated on silicon wafers, which can lead to the miniaturization of implantable devices due to the possible reduction or even elimination of battery size. To evaluate this possibility, the antenna must be tested in conditions close to real working conditions, requiring the use of human body phantoms. This paper proposes a solution to measure the power received by an ultra-small antenna placed inside a phantom, without the use of coaxial cables attached to the device. Instead, an optoelectronic mechanism is used to route the received power to an optical fiber, and an optical spectrum analyzer is used to measure the received power.This work was supported by Portuguese Foundation for Science and Technology: FCT-PTDC/EEI-TEL/2881/2012, Programa Operacional Temático Fatores de Competitividade (COMPETE) and Fundo Comunitário Europeu FEDER.info:eu-repo/semantics/publishedVersio

Performance evaluation of IB-DFE-based strategies for SC-FDMA systems

The aim of this paper is to propose and evaluate multi-user iterative block decision feedback equalization (IB-DFE) schemes for the uplink of single-carrier frequency-division multiple access (SC-FDMA)-based systems. It is assumed that a set of single antenna users share the same physical channel to transmit its own information to the base station, which is equipped with an antenna array. Two space-frequency multi-user IB-DFE-based processing are considered: iterative successive interference cancellation and parallel interference cancellation. In the first approach, the equalizer vectors are computed by minimizing the mean square error (MSE) of each individual user, at each subcarrier. In the second one, the equalizer matrices are obtained by minimizing the overall MSE of all users at each subcarrier. For both cases, we propose a simple yet accurate analytical approach for obtaining the performance of the discussed receivers. The proposed schemes allow an efficient user separation, with a performance close to the one given by the matched filter bound for severely time-dispersive channels, with only a few iterations

On-chip, efficient and small antenna array for millimeter-wave applications

The high path losses experienced by wireless applications at millimeter wavelengths may be mitigated using high gain antennas. The intrinsic small wavelengths makes very attractive to develop solutions with on-chip integrated antennas. However, due to silicon high losses, on-chip antenna elements on RFCMOS technology have reduced efficiency. This paper proposes a solution to obtain an on-chip integrated antenna array based on 3D efficient antenna elements. A 4 element antenna was designed to operate at 57.5 GHz central frequency, with maximum gain of 5.8 dB, and maximum expected efficiency of 45%.Work supported by Portuguese Foundation for Science and Technology (SFRH/BD/63737/2009, and PTDC/ EEI-TEL/ 2881/2012, Programa Operacional Temático Fatores de Competitividade-COMPETE, and Fundo Comunitário Europeu-FEDER).info:eu-repo/semantics/publishedVersio

A multiantenna approach to maximize wireless power transfered to implantable devices

Power delivery from an external source to implanted devices through wireless links is hindered by SAR regulations, which limit the amount of power radiated by an external source that reaches an implant. In order to increase the power delivered to the implant, we studied a solution with two transmitters and compared results with the common single transmitter link. HFSS and COMSOL have been used to show that a power increase of around 40% inside a human head model was achieved while respecting SAR limits and keeping tissue temperature under control, stabilizing at around 37.4 degrees C.- Work supported by FCT under project PTDC/EEI-TEL/5250/2014, by FEDER funds through Projeto 3599 - Promover a Producao Cientifica e Desenvolvimento Tecnologico e a Constituicao de Redes Tematicas (3599-PPCDT).info:eu-repo/semantics/publishedVersio

Information and flux in a feedback controlled Brownian ratchet

We study a feedback control version of the flashing Brownian ratchet, in which the application of the flashing potential depends on the state of the particles to be controlled. Taking the view that the ratchet acts as a Maxwell's demon, we study the relationship that exists between the performance of the demon as a rectifier of random motion and the amount of information gathered by the demon through measurements. In the context of a simple measurement model, we derive analytic expressions for the flux induced by the feedback ratchet when acting on one particle and a few particles, and compare these results with those obtained with its open-loop version, which operates without information. Our main finding is that the flux in the feedback case has an upper bound proportional to the square-root of the information. Our results provide a quantitative analysis of the value of information in feedback ratchets, as well as an effective description of imperfect or noisy feedback ratchets that are relevant for experimental applications.Comment: LaTeX, 13 pages, 2 figure

Influence of Genetic Polymorphisms in Prostaglandin E2 Pathway (COX-2/HPGD/SLCO2A1/ABCC4) on the Risk for Colorectal Adenoma Development and Recurrence after Polypectomy

OBJECTIVES: Deregulation of prostaglandin E2 (PGE2) levels reported in colorectal carcinogenesis contributes to key steps of cancer development. Our aim was to evaluate the influence of the genetic variability in COX-2/HPGD/SLCO2A1/ABCC4 PGE2 pathway genes on the development and recurrence of colorectal adenomas. METHODS: A case-control study was conducted gathering 480 unscreened individuals and 195 patients with personal history of adenomas. A total of 43 tagSNPs were characterized using the Sequenom platform or real-time PCR. RESULTS: Ten tagSNPs were identified as susceptibility biomarkers for the development of adenomas. The top three most meaningful tagSNPs include the rs689466 in COX-2 (odds ratio (OR)=3.23; 95% confidence interval (CI): 1.52-6.86), rs6439448 in SLCO2A1 (OR=0.38; 95% CI: 0.22-0.65) and rs1751051 in ABCC4 genes (OR=2.75; 95% CI: 1.58-4.80). The best four-locus gene-gene interaction model included the rs1346271, rs1863642 and rs12500316 single nucleotide polymorphisms in HPGD and rs1678405 in ABCC4 genes and was associated with a 13-fold increased susceptibility (95% CI: 3.84-46.3, P<0.0001, cross-validation (CV) accuracy: 0.78 and CV consistency: 8/10). Interesting, in low-risk patients the ABCC4 rs9524821AA genotype was associated not only with a higher hazard ratio (HR=2.93; 95% CI: 1.07-8.03), but half of these patients had adenoma recurrence at 60 months, considerably higher than the 21% noticed in low-risk patients. CONCLUSIONS: Genetic polymorphisms in COX-2/PGE2 pathway appear to contribute to the development of colorectal adenomas and influence the interval time to adenomas recurrence. The definition of risk models through the inclusion of genetic biomarkers might improve the adherence and optimization of current screening and surveillance guidelines for colorectal cancer prevention.Financial support: This study was supported by a research grant from the Instituto Português de Oncologia do Porto— Centro de Investigação. Furthermore, C.P. was a recipient of a PhD grant (SFRH/BD/64805/2009) from FCT— Fundacão para a Ciência e Tecnologia, co-financed by European Social Funds (ESF) under Human Potential Operation Programme (POPH) from National Strategic Reference Framework (NSRF) and Liga Portuguesa Contra o Cancro—Núcleo Regional do Norte. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio

Thermodynamics of adiabatic feedback control

We study adaptive control of classical ergodic Hamiltonian systems, where the controlling parameter varies slowly in time and is influenced by system's state (feedback). An effective adiabatic description is obtained for slow variables of the system. A general limit on the feedback induced negative entropy production is uncovered. It relates the quickest negentropy production to fluctuations of the control Hamiltonian. The method deals efficiently with the entropy-information trade off.Comment: 6 pages, 1 figur