Ultra-thin and flexible CMOS technology: ISFET-based microsystem for biomedical applications

A new paradigm of silicon technology is the ultra-thin chip (UTC) technology and the emerging applications. Very thin integrated circuits (ICs) with through-silicon vias (TSVs) will allow the stacking and interconnection of multiple dies in a compact format allowing a migration towards three-dimensional ICs (3D-ICs). Also, extremely thin and therefore mechanically bendable silicon chips in conjunction with the emerging thin-film and organic semiconductor technologies will enhance the performance and functionality of large-area flexible electronic systems. However, UTC technology requires special attention related to the circuit design, fabrication, dicing and handling of ultra-thin chips as they have different physical properties compared to their bulky counterparts. Also, transistors and other active devices on UTCs experiencing variable bending stresses will suffer from the piezoresistive effect of silicon substrate which results in a shift of their operating point and therefore, an additional aspect should be considered during circuit design. This thesis tries to address some of these challenges related to UTC technology by focusing initially on modelling of transistors on mechanically bendable Si-UTCs. The developed behavioural models are a combination of mathematical equations and extracted parameters from BSIM4 and BSIM6 modified by a set of equations describing the bending-induced stresses on silicon. The transistor models are written in Verilog-A and compiled in Cadence Virtuoso environment where they were simulated at different bending conditions. To complement this, the verification of these models through experimental results is also presented. Two chips were designed using a 180 nm CMOS technology. The first chip includes nMOS and pMOS transistors with fixed channel width and two different channel lengths and two different channel orientations (0° and 90°) with respect to the wafer crystal orientation. The second chip includes inverter logic gates with different transistor sizes and orientations, as in the previous chip. Both chips were thinned down to ∼20m using dicing-before-grinding (DBG) prior to electrical characterisation at different bending conditions. Furthermore, this thesis presents the first reported fully integrated CMOS-based ISFET microsystem on UTC technology. The design of the integrated CMOS-based ISFET chip with 512 integrated on-chip ISFET sensors along with their read-out and digitisation scheme is presented. The integrated circuits (ICs) are thinned down to ∼30m and the bulky, as well as thinned ICs, are electrically and electrochemically characterised. Also, the thesis presents the first reported mechanically bendable CMOS-based ISFET device demonstrating that mechanical deformation of the die can result in drift compensation through the exploitation of the piezoresistive nature of silicon. Finally, this thesis presents the studies towards the development of on-chip reference electrodes and biodegradable and ultra-thin biosensors for the detection of neurotransmitters such as dopamine and serotonin

Dispositivos médicos em cardiologia

Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2014O objetivo desta revisão é abordar os Dispositivos Médicos usados em Cardiologia e em particular os aplicados em caso de Insuficiência Cardíaca (IC). Os métodos basearam-se na pesquisa de artigos nas bases de dados PubMed, B-On e ScienceDirect. A insuficiência cardíaca é um dos principais problemas não resolvidos em cardiologia e uma das principais causas de morte. Os dispositivos médicos CircuLite Synergy e Parachute são dispositivos inovadores que têm proporcionado melhorias hemodinâmicas significativas em doentes com insuficiência cardíaca, permitindo uma melhoria da sua qualidade de vida. O dispositivo CircuLite Synergy é um sistema implantável pouco invasivo que potencia a recuperação da função cardíaca, tendo já sido demonstrada a sua efetividade na remodelação reversa do ventrículo esquerdo (VE). Contudo, são necessários mais estudos para otimizar a relação risco-benefício deste dispositivo. O dispositivo Parachute permite a restauração da geometria do VE, estabilizando a sua remodelação. Uma potencial aplicação deste tratamento consiste numa intervenção mais precoce com este dispositivo, o que poderá prevenir o processo de remodelação ventricular e retardar o aparecimento da IC.The aim of this review is to describe the Medical Devices used in Cardiology particularly those that are applied to Heart Failure. The research methodology was centered in electronic database search PubMed, B-On and Science Direct. Heart failure is one of the major unsolved problems in cardiology and one of the leading causes of death. Parachute and CircuLite Synergy are innovative medical devices that have enhanced the hemodynamic significantly in patients with heart failure, contributing to the improvement of their quality of life. The CircuLite Synergy medical device is a minimally invasive implantable system that promotes the recovery of heart function. In addition, it has already demonstrated its effectiveness in left ventricular (LV) reverse remodeling. However, more studies are needed to optimize its risk-benefit ratio. The Parachute medical device allows the patients to restore the geometry of LV, stabilizing its remodeling. One potential application of this treatment is an earlier intervention with this device, which may prevent the patients from ventricular remodeling as well as retard the occurrence of heart failure