Design and experimental characterization of antennas and wireless systems for innovative wearable and implantable ultra low–power applications

The present PhD thesis exploits the design skills I have been improving since my master thesis’ research. A brief description of the chapters’ content follows. Chapter 1: the simulation of a complete front–end is a very complex problem and, in particular, is the basis upon which the prediction of the overall performance of the system is possible. By means of a commercial EM simulation tool and a rigorous nonlinear/EM circuit co–simulation based on the Reciprocity Theorem, the above–mentioned prediction can be achieved and exploited for wireless links characterization. This will represent the theoretical basics of the entire present thesis and will be supported by two RF applications. Chapter 2: an extensive dissertation about Magneto–Dielectric (MD) materials will be presented, together with their peculiar characteristics as substrates for antenna miniaturization purposes. A designed and tested device for RF on–body applications will be described in detail. Finally, future research will be discussed. Chapter 3: this chapter will deal with the issue regarding the exploitation of renewable energy sources for low–energy consumption devices. Hence the problem related to the so–called energy harvesting will be tackled and a first attempt to deploy THz solar energy in an innovative way will be presented and discussed. Future research will be proposed as well. Chapter 4: graphene is a very promising material for devices to be exploited in the RF and THz frequency range for a wide range of engineering applications, including those ones marked as the main research goal of the present thesis. This chapter will present the results obtained during my research period at the National Institute for Research and Development in Microtechnologies (IMT) in Bucharest, Romania. It will concern the design and manufacturing of antennas and diodes made in graphene–based technology for detection/rectification purposes.

Design and Fabrication of Bond Wire Micro-Magnetics

This thesis presents a new approach for the design and fabrication of bond wire magnetics for power converter applications by using standard IC gold bonding wires and micro-machined magnetic cores. It shows a systematic design and characterization study for bond wire transformers with toroidal and race-track cores for both PCB and silicon substrates. Measurement results show that the use of ferrite cores increases the secondary self-inductance up to 315 µH with a Q-factor up to 24.5 at 100 kHz. Measurement results on LTCC core report an enhancement of the secondary self-inductance up to 23 µH with a Q-factor up to 10.5 at 1.4 MHz. A resonant DC-DC converter is designed in 0.32 µm BCD6s technology at STMicroelectronics with a depletion nmosfet and a bond wire micro-transformer for EH applications. Measures report that the circuit begins to oscillate from a TEG voltage of 280 mV while starts to convert from an input down to 330 mV to a rectified output of 0.8 V at an input of 400 mV. Bond wire magnetics is a cost-effective approach that enables a flexible design of inductors and transformers with high inductance and high turns ratio. Additionally, it supports the development of magnetics on top of the IC active circuitry for package and wafer level integrations, thus enabling the design of high density power components. This makes possible the evolution of PwrSiP and PwrSoC with reliable highly efficient magnetics.

Design and Synthesis of Naphthalene Diimides Based Small Molecules as Anticancer Agents: Targeting the Polyamine Transporter, G-quadruplex Structures and HDAC

Cancer is a multifactorial disease characterized by a very complex etiology. Basing on its complex nature, a promising therapeutic strategy could be based by the “Multi-Target-Directed Ligand” (MTDL) approach, based on the assumption that a single molecule could hit several targets responsible for the pathology. Several agents acting on DNA are clinically used, but the severe deriving side effects limit their therapeutic application. G-quadruplex structures are DNA secondary structures located in key zones of human genome; targeting quadruplex structures could allow obtaining an anticancer therapy more free from side effects. In the last years it has been proved that epigenetic modulation can control the expression of human genes, playing a crucial role in carcinogenesis and, in particular, an abnormal expression of histone deacetylase enzymes are related to tumor onset and progression. This thesis deals with the design and synthesis of new naphthalene diimide (NDI) derivatives endowed with anticancer activity, interacting with DNA together with other targets implicated in cancer development, such as HDACs. NDI-polyamine and NDI-polyamine-hydroxamic acid conjugates have been designed with the aim to provide potential MTDLs, in order to create molecules able simultaneously to interact with different targets involved in this pathology, specifically the G-quadruplex structures and HDAC, and to exploit the polyamine transport system to get selectively into cancer cells. Macrocyclic NDIs have been designed with the aim to improve the quadruplex targeting profile of the disubstituted NDIs. These compounds proved the ability to induce a high and selective stabilization of the quadruplex structures, together with cytotoxic activities in the micromolar range. Finally, trisubstituted NDIs have been developed as G-quadruplex-binders, potentially effective against pancreatic adenocarcinoma. In conclusion, all these studies may represent a promising starting point for the development of new interesting molecules useful for the treatment of cancer, underlining the versatility of the NDI scaffold.

Design and Characterization of Luminescent Silica Nanoparticles

The aim of this thesis was to design, synthesize and characterize dye-doped silica nanoparticles (DDSNPs) to be used as chemosensors or labels in bioanalytical applications. DDSNPs represent one of the most versatile and useful components in nanomedicine displaying important features such as high colloid stability in water, low toxicity, one-pot inexpensive synthesis and tunable fluorescence emission. Starting from the one-pot and highly reproducible synthesis of “silica-core/PEG shell” DDSNPs based on the use of micelles of Pluronic F127, in which take place both hydrolysis and condensation of the silica precursor and of the dyes functionalized with a triethoxysilane group, we developed DDSNPs suitable for optical and optoacustic imaging, drug loading and chemical sensing obtaining very interesting results for the further development of nanomedicine.

The Design and Analysis of Partner Studies of HIV Transmission

Common goals in epidemiologic studies of infectious diseases include identification of the infectious agent, description of the modes of transmission and characterization of factors that influence the probability of transmission from infected to uninfected individuals. In the case of AIDS, the agent has been identified as the Human Immunodeficiency Virus (HIV), and transmission is known to occur through a variety of contact mechanisms including unprotected sexual intercourse, transfusion of infected blood products and sharing of needles in intravenous drug use. Relatively little is known about the probability of IV transmission associated with the various modes of contact, or the role that other cofactors play in promoting or suppressing transmission. Here, transmission probability refers to the probability that the virus is transmitted to a susceptible individual following exposure consisting of a series of potentially infectious contacts. The infectivity of HIV for a given route of transmission is defined to be the per contact probability of infection. Knowledge of infectivity and its relationship to other factors is important in understanding the dynamics of the AIDS epidemic and in suggesting appropriate measures to control its spread. The primary source of empirical data about infectivity comes from sexual partners of infected individuals. Partner studies consist of a series of such partnerships, usually heterosexual and monogamous, each composed of an initially infected "index case" and a partner who may or may not be infected by the time of data collection. However, because the infection times of both partners may be unknown and the history of contacts uncertain, any quantitative characterization of infectivity is extremely difficult. Thus, most statistical analyses of partner study data involve the simplifying assumption that infectivity is a constant common to all partnerships. The major objectives of this work are to describe and discuss the design and analysis of partner studies, providing a general statistical framework for investigations of infectivity and risk factors for HIV transmission. The development is largely based on three papers: Jewell and Shiboski (1990), Kim and Lagakos (1990), and Shiboski and Jewell (1992).

Review of assessment, design, and mitigation of multiple hazards

Large parts of the world are subjected to one or more natural hazards, such as earthquakes, tsunamis, landslides, tropical storms (hurricanes, cyclones and typhoons), costal inundation and flooding. Virtually the entire world is at risk of man-made hazards. In recent decades, rapid population growth and economic development in hazard-prone areas have greatly increased the potential of multiple hazards to cause damage and destruction of buildings, bridges, power plants, and other infrastructure; thus posing a grave danger to the community and disruption of economic and societal activities. Although an individual hazard is significant in many parts of the United States (U.S.), in certain areas more than one hazard may pose a threat to the constructed environment. In such areas, structural design and construction practices should address multiple hazards in an integrated manner to achieve structural performance that is consistent with owner expectations and general societal objectives. The growing interest and importance of multiple-hazard engineering has been recognized recently. This has spurred the evolution of multiple-hazard risk-assessment frameworks and development of design approaches which have paved way for future research towards sustainable construction of new and improved structures and retrofitting of the existing structures. This report provides a review of literature and the current state of practice for assessment, design and mitigation of the impact of multiple hazards on structural infrastructure. It also presents an overview of future research needs related to multiple-hazard performance of constructed facilities.

DESIGN AND FABRICATION OF RESONANT GAS SENSOR FOR HIGH SENSITIVITY IN THE PRESENCE OF AIR DAMPING

Gas sensors have been used widely in different important area including industrial control, environmental monitoring, counter-terrorism and chemical production. Micro-fabrication offers a promising way to achieve sensitive and inexpensive gas sensors. Over the years, various MEMS gas sensors have been investigated and fabricated. One significant type of MEMS gas sensors is based on mass change detection and the integration with specific polymer. This dissertation aims to make contributions to the design and fabrication of MEMS resonant mass sensors with capacitance actuation and sensing that lead to improved sensitivity. To accomplish this goal, the research has several objectives: (1) Define an effective measure for evaluating the sensitivity of resonant mass devices; (2) Model the effects of air damping on microcantilevers and validate models using laser measurement system (3) Develop design guidelines for improving sensitivity in the presence of air damping; (4) Characterize the degree of uncertainty in performance arising from fabrication variation for one or more process sequences, and establish design guidelines for improved robustness. Work has been completed toward these objectives. An evaluation measure has been developed and compared to an RMS based measure. Analytic models of air damping for parallel plate that include holes are compared with a COMSOL model. The models have been used to identify cantilever design parameters that maximize sensitivity. Additional designs have been modeled with COMSOL and the development of an analytical model for Fixed-free cantilever geometries with holes has been developed. Two process flows have been implemented and compared. A number of cantilever designs have been fabricated and the uncertainty in process has been investigated. Variability from processing have been evaluated and characterized.

DESIGN AND IMPLEMENT DYNAMIC PROGRAMMING BASED DISCRETE POWER LEVEL SMART HOME SCHEDULING USING FPGA

With the development and capabilities of the Smart Home system, people today are entering an era in which household appliances are no longer just controlled by people, but also operated by a Smart System. This results in a more efficient, convenient, comfortable, and environmentally friendly living environment. A critical part of the Smart Home system is Home Automation, which means that there is a Micro-Controller Unit (MCU) to control all the household appliances and schedule their operating times. This reduces electricity bills by shifting amounts of power consumption from the on-peak hour consumption to the off-peak hour consumption, in terms of different “hour price”. In this paper, we propose an algorithm for scheduling multi-user power consumption and implement it on an FPGA board, using it as the MCU. This algorithm for discrete power level tasks scheduling is based on dynamic programming, which could find a scheduling solution close to the optimal one. We chose FPGA as our system’s controller because FPGA has low complexity, parallel processing capability, a large amount of I/O interface for further development and is programmable on both software and hardware. In conclusion, it costs little time running on FPGA board and the solution obtained is good enough for the consumers.

Ontologies and Methods for Interoperability of Engineering Analysis Models (EAMS) in an E-Design Environment

ABSTRACT ONTOLOGIES AND METHODS FOR INTEROPERABILITY OF ENGINEERING ANALYSIS MODELS (EAMS) IN AN E-DESIGN ENVIRONMENT SEPTEMBER 2007 NEELIMA KANURI, B.S., BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCES PILANI INDIA M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Ian Grosse Interoperability is the ability of two or more systems to exchange and reuse information efficiently. This thesis presents new techniques for interoperating engineering tools using ontologies as the basis for representing, visualizing, reasoning about, and securely exchanging abstract engineering knowledge between software systems. The specific engineering domain that is the primary focus of this report is the modeling knowledge associated with the development of engineering analysis models (EAMs). This abstract modeling knowledge has been used to support integration of analysis and optimization tools in iSIGHT FD , a commercial engineering environment. ANSYS , a commercial FEA tool, has been wrapped as an analysis service available inside of iSIGHT-FD. Engineering analysis modeling (EAM) ontology has been developed and instantiated to form a knowledge base for representing analysis modeling knowledge. The instances of the knowledge base are the analysis models of real world applications. To illustrate how abstract modeling knowledge can be exploited for useful purposes, a cantilever I-Beam design optimization problem has been used as a test bed proof-of-concept application. Two distinct finite element models of the I-beam are available to analyze a given beam design- a beam-element finite element model with potentially lower accuracy but significantly reduced computational costs and a high fidelity, high cost, shell-element finite element model. The goal is to obtain an optimized I-beam design at minimum computational expense. An intelligent KB tool was developed and implemented in FiPER . This tool reasons about the modeling knowledge to intelligently shift between the beam and the shell element models during an optimization process to select the best analysis model for a given optimization design state. In addition to improved interoperability and design optimization, methods are developed and presented that demonstrate the ability to operate on ontological knowledge bases to perform important engineering tasks. One such method is the automatic technical report generation method which converts the modeling knowledge associated with an analysis model to a flat technical report. The second method is a secure knowledge sharing method which allocates permissions to portions of knowledge to control knowledge access and sharing. Both the methods acting together enable recipient specific fine grain controlled knowledge viewing and sharing in an engineering workflow integration environment, such as iSIGHT-FD. These methods together play a very efficient role in reducing the large scale inefficiencies existing in current product design and development cycles due to poor knowledge sharing and reuse between people and software engineering tools. This work is a significant advance in both understanding and application of integration of knowledge in a distributed engineering design framework.

Design and establishment of a biobank in a multicenter prospective cohort study of elderly patients with venous thromboembolism (SWITCO65+)

In the field of thrombosis and haemostasis, many preanalytical variables influence the results of coagulation assays and measures to limit potential results variations should be taken. To our knowledge, no paper describing the development and maintenance of a haemostasis biobank has been previously published. Our description of the biobank of the Swiss cohort of elderly patients with venous thromboembolism (SWITCO65+) is intended to facilitate the set-up of other biobanks in the field of thrombosis and haemostasis. SWITCO65+ is a multicentre cohort that prospectively enrolled consecutive patients aged ≥65 years with venous thromboembolism at nine Swiss hospitals from 09/2009 to 03/2012. Patients will be followed up until December 2013. The cohort includes a biobank with biological material from each participant taken at baseline and after 12 months of follow-up. Whole blood from all participants is assayed with a standard haematology panel, for which fresh samples are required. Two buffy coat vials, one PAXgene Blood RNA System tube and one EDTA-whole blood sample are also collected at baseline for RNA/DNA extraction. Blood samples are processed and vialed within 1 h of collection and transported in batches to a central laboratory where they are stored in ultra-low temperature archives. All analyses of the same type are performed in the same laboratory in batches. Using multiple core laboratories increased the speed of sample analyses and reduced storage time. After recruiting, processing and analyzing the blood of more than 1,000 patients, we determined that the adopted methods and technologies were fit-for-purpose and robust.

Design and evaluation of the parent education component of a comprehensive violence prevention project in middle schools

Low parental monitoring is related to youth risk behaviors such as delinquency and aggression. The purpose of this dissertation was to describe the development and evaluation of a parent education intervention to increase parental monitoring in Hispanic parents of middle school children.^ The first study described the process of intervention mapping as used to develop Padres Trabajando por la Paz, a newsletter intervention for parents. Using theory, empirical literature, and information from the target population, performance objectives and determinants for monitoring were defined. Learning objectives were specified and a staged social-cognitive approach was used to develop methods and strategies delivered through newsletters.^ The second study examined the outcomes of a randomized trial of the newsletter intervention. Outcome measures consisted of a general measure of monitoring, parent and child reports of monitoring behaviors targeted by the intervention, and psychosocial determinants of monitoring (self-efficacy, norms, outcome expectancies, knowledge, and beliefs). Seventy-seven parents completed the randomized trial, half of which received four newsletters over an eight-week period. Results revealed a significant interaction effect for baseline and treatment for parent's reports of norms for monitoring (p =.009). Parents in the experimental condition who scored low at baseline reported increased norms for monitoring at follow-up. A significant interaction effect for child reports of parental monitoring behaviors (p =.04) reflected an small increase across baseline levels in the experimental condition and decreases for the control condition at higher baseline scores. Both groups of parents reported increased levels of monitoring at follow-up. No other outcome measures varied significantly by condition.^ The third study examined the relationship between the psychosocial determinants of parental monitoring and parental monitoring behaviors in the study population. Weak evidence for a relationship between outcome expectancies and parental monitoring behaviors suggests further research in the area utilizing stronger empirical models such as longitudinal design and structural equation modeling.^ The low-cost, minimal newsletter intervention showed promise for changing norms among Hispanic parents for parental monitoring. In light of the importance of parental monitoring as a protective factor for youth health risk behaviors, more research needs to be done to develop and evaluate interventions to increase parental monitoring. ^

National competence center for wildlife diseases in Switzerland: Mandate, development and current strategies.

The need for wildlife health surveillance has become increasingly recognized. However, comprehensive programs which cover a wide spectrum of species, pathogens and geographic areas are still lacking in most European countries and practical examples of systems in place remain scarce. This article provides an overview of the organization of wildlife health surveillance in Switzerland, with a focus on the development, current strategies and the activities of the national program carried out by the Centre for Fish and Wildlife Health (FIWI), University of Bern. This documentation may stimulate on-going discussions on the design and development of national wildlife health surveillance programs in other countries. Investigations into wildlife health in Switzerland date back to the 1950s. The FIWI acts as a national competence center for wildlife diseases on mandate of the Swiss federal authorities. The mandate includes four main activities: disease diagnostics, research, consulting and teaching. In line with this, the FIWI has made continuous efforts to strengthen a national network of field partners and implemented strategies to facilitate long-term and metastudies.

A summative evaluation of a HIV/AIDS Early Childhood Care, Education and Development Teacher Training Workshop in Mongu, Zambia

Objective. To conduct a summative evaluation of an Early Childhood Care, Education and Development (ECCED) Teacher Training Workshop in Mongu, Zambia by assessing changes in knowledge, attitudes and intent to use the information. ^ Study design. A matched cohort survey design was used with additional qualitative data collected by structured observation of workshop sessions, daily facilitator and participant debriefs and participant interviews. ^ Results. Matching pre and post tests were completed by 27 individuals in addition to daily debriefs, structured workshop observation and participant interviews with 22% of the group. The participant population was predominantly female individuals aged 15-44 years old that had completed high school and additional post-secondary training, been teaching children aged 0 – 8 years for 2-5 years in the Western Province and received other HIV/AIDS and ECCED education. Pre-tests indicated a strong understanding of ECCED principles and misconceptions regarding HIV transmission, prevention and the disease's impact on early childhood development. The workshop was found to significantly increase the participants' knowledge of topics covered by the curriculum (paired t-test, N=27, p = 0.004, 95% CI 1.8, 8.6). Participants began with a more limited understanding of HIV/AIDS than ECCED, but the mean gain was much greater at 7.4 +/- 12.3 points. Significantly more participants believed at post-test that HIV/AIDS education should increase for future educators. The 77.8% of participants that increased their knowledge scores at post-test expressed significantly less fear of having a child with HIV/AIDS in the classroom (Independent Samples t-test, N= 27, p = 0.011). Overall participant fear decreased 15.5%. 92.6% and 88.9% of participants planned at post-test to respectively use and share the taught information in their daily professional lives and reported on innovative strategies to communicate with the community. ^ Conclusions. Teacher training workshops can significantly increase HIV/AIDS awareness and promote positive attitudes in educators working with children affected by HIV/AIDS. Using participant suggested teaching techniques such as poems and songs and translating the materials to the local language could assist future facilitators to both culturally and professionally relate to the workshop audience as well as increase participant capacity to share the information with the local community. ^

STRATEGIES FOR THE TRANSFER OF APPROPRIATE TECHNOLOGY TO DEVELOPING COUNTRIES: THE IMPLEMENTATION AND DEVELOPMENT OF ENVIRONMENTAL HEALTH PROGRAMS IN TUNISIA

This dissertation focuses on Project HOPE, an American medical aid agency, and its work in Tunisia. More specifically this is a study of the implementation strategies of those HOPE sponsored projects and programs designed to solve the problems of high morbidity and infant mortality rates due to environmentally related diarrheal and enteric diseases. Several environmental health programs and projects developed in cooperation with Tunisian counterparts are described and analyzed. These include (1) a paramedical manpower training program; (2) a national hospital sanitation and infection control program; (3) a community sewage disposal project; (4) a well reconstruction project; and (5) a solid-waste disposal project for a hospital.^ After independence, Tunisia, like many developing countries, encountered several difficulties which hindered progress toward solving basic environmental health problems and prompted a request for aid. This study discusses the need for all who work in development programs to recognize and assess those difficulties or constraints which affect the program planning process, including those latent cultural and political constraints which not only exist within the host country but within the aid agency as well. For example, failure to recognize cultural differences may adversely affect the attitudes of the host staff towards their work and towards the aid agency and its task. These factors, therefore, play a significant role in influencing program development decisions and must be taken into account in order to maximize the probability of successful outcomes.^ In 1969 Project HOPE was asked by the Tunisian government to assist the Ministry of Health in solving its health manpower problems. HOPE responded with several programs, one of which concerned the training of public health nurses, sanitary technicians, and aids at Tunisia's school of public health in Nabeul. The outcome of that program as well as the strategies used in its development are analyzed. Also, certain questions are addressed such as, what should the indicators of success be, and when is the time right to phase out?^ Another HOPE program analyzed involved hospital sanitation and infection control. Certain generic aspects of basic hospital sanitation procedures were documented and presented in the form of a process model which was later used as a "microplan" in setting up similar programs in other Tunisian hospitals. In this study the details of the "microplan" are discussed. The development of a nation-wide program without any further need of external assistance illustrated the success of HOPE's implementation strategies.^ Finally, although it is known that the high incidence of enteric disease in developing countries is due to poor environmental sanitation and poor hygiene practices, efforts by aid agencies to correct these conditions have often resulted in failure. Project HOPE's strategy was to maximize limited resources by using a systems approach to program development and by becoming actively involved in the design and implementation of environmental health projects utilizing "appropriate" technology. Three innovative projects and their implementation strategies (including technical specifications) are described.^ It is advocated that if aid agencies are to make any progress in helping developing countries basic sanitation problems, they must take an interdisciplinary approach to progrm development and play an active role in helping counterparts seek and identify appropriate technologies which are socially and economically acceptable. ^

Research on intermediate band solar cells and development of experimental techniques for their characterization under concentrated illumination

Abstract This work is a contribution to the research and development of the intermediate band solar cell (IBSC), a high efficiency photovoltaic concept that features the advantages of both low and high bandgap solar cells. The resemblance with a low bandgap solar cell comes from the fact that the IBSC hosts an electronic energy band -the intermediate band (IB)- within the semiconductor bandgap. This IB allows the collection of sub-bandgap energy photons by means of two-step photon absorption processes, from the valence band (VB) to the IB and from there to the conduction band (CB). The exploitation of these low energy photons implies a more efficient use of the solar spectrum. The resemblance of the IBSC with a high bandgap solar cell is related to the preservation of the voltage: the open-circuit voltage (VOC) of an IBSC is not limited by any of the sub-bandgaps (involving the IB), but only by the fundamental bandgap (defined from the VB to the CB). Nevertheless, the presence of the IB allows new paths for electronic recombination and the performance of the IBSC is degraded at 1 sun operation conditions. A theoretical argument is presented regarding the need for the use of concentrated illumination in order to circumvent the degradation of the voltage derived from the increase in the recombi¬nation. This theory is supported by the experimental verification carried out with our novel characterization technique consisting of the acquisition of photogenerated current (IL)-VOC pairs under low temperature and concentrated light. Besides, at this stage of the IBSC research, several new IB materials are being engineered and our novel character¬ization tool can be very useful to provide feedback on their capability to perform as real IBSCs, verifying or disregarding the fulfillment of the “voltage preservation” principle. An analytical model has also been developed to assess the potential of quantum-dot (QD)-IBSCs. It is based on the calculation of band alignment of III-V alloyed heterojunc-tions, the estimation of the confined energy levels in a QD and the calculation of the de¬tailed balance efficiency. Several potentially useful QD materials have been identified, such as InAs/AlxGa1-xAs, InAs/GaxIn1-xP, InAs1-yNy/AlAsxSb1-x or InAs1-zNz/Alx[GayIn1-y]1-xP. Finally, a model for the analysis of the series resistance of a concentrator solar cell has also been developed to design and fabricate IBSCs adapted to 1,000 suns. Resumen Este trabajo contribuye a la investigación y al desarrollo de la célula solar de banda intermedia (IBSC), un concepto fotovoltaico de alta eficiencia que auna las ventajas de una célula solar de bajo y de alto gap. La IBSC se parece a una célula solar de bajo gap (o banda prohibida) en que la IBSC alberga una banda de energía -la banda intermedia (IB)-en el seno de la banda prohibida. Esta IB permite colectar fotones de energía inferior a la banda prohibida por medio de procesos de absorción de fotones en dos pasos, de la banda de valencia (VB) a la IB y de allí a la banda de conducción (CB). El aprovechamiento de estos fotones de baja energía conlleva un empleo más eficiente del espectro solar. La semejanza antre la IBSC y una célula solar de alto gap está relacionada con la preservación del voltaje: la tensión de circuito abierto (Vbc) de una IBSC no está limitada por ninguna de las fracciones en las que la IB divide a la banda prohibida, sino que está únicamente limitada por el ancho de banda fundamental del semiconductor (definido entre VB y CB). No obstante, la presencia de la IB posibilita nuevos caminos de recombinación electrónica, lo cual degrada el rendimiento de la IBSC a 1 sol. Este trabajo argumenta de forma teórica la necesidad de emplear luz concentrada para evitar compensar el aumento de la recom¬binación de la IBSC y evitar la degradación del voltage. Lo anterior se ha verificado experimentalmente por medio de nuestra novedosa técnica de caracterización consistente en la adquisicin de pares de corriente fotogenerada (IL)-VOG en concentración y a baja temperatura. En esta etapa de la investigación, se están desarrollando nuevos materiales de IB y nuestra herramienta de caracterizacin está siendo empleada para realimentar el proceso de fabricación, comprobando si los materiales tienen capacidad para operar como verdaderas IBSCs por medio de la verificación del principio de preservación del voltaje. También se ha desarrollado un modelo analítico para evaluar el potencial de IBSCs de puntos cuánticos. Dicho modelo está basado en el cálculo del alineamiento de bandas de energía en heterouniones de aleaciones de materiales III-V, en la estimación de la energía de los niveles confinados en un QD y en el cálculo de la eficiencia de balance detallado. Este modelo ha permitido identificar varios materiales de QDs potencialmente útiles como InAs/AlxGai_xAs, InAs/GaxIni_xP, InAsi_yNy/AlAsxSbi_x ó InAsi_zNz/Alx[GayIni_y]i_xP. Finalmente, también se ha desarrollado un modelado teórico para el análisis de la resistencia serie de una célula solar de concentración. Gracias a dicho modelo se han diseñado y fabricado IBSCs adaptadas a 1.000 soles.