Chemotactic behavior of catalytic motors in microfluidic channels

Chemotaxis in practice: Two different artificial catalytic micromotors (tubular and spherical, see scheme) show chemotactic behavior in microfluidic channels demonstrating that catalytic micromotors can sense the gradient of chemical fuel in their environment and be directed towards desired locations

La competencia "aprender a aprender" en un contexto educativo de ingeniería

The objective of this thesis was to establish bases to characterize "learn to learn" competence and to promote it in an engineering educational context. It adopted the vision of educational psychology that establishes self-regulation in learning as the operative manifestation of this competence. The research was developed in three phases: obtaining a psychometric tool to characterize self-regulation in learning; the characterization of self-regulation in learning of the students; and, based on the results of the characterization, an educational intervention was designed, implemented and evaluated to facilitate that students use the learning strategy of selection and organization of the information . In the first phase in order to obtain the psychometric tool was translated, adapted and validated the Motivated Strategies for Learning Questionnaire - MSLQ following the guidelines of the International Test Commission (ITC). The result was the MSLQ-Colombia. With the participation of 1218 students and 12 engineering professors, the psychometric properties of MSLQ-Colombia were studied: construct validity, content validity, external validity and reliability; the MSLQ-Colombia was valid and reliable. In the characterization, second phase, the self-regulation of the motivation and the use of learning strategies of 1268 students were evaluated. It was found that students self-regulate their motivation highly: beliefs about learning control and task value were the aspects most self-regulated, while the learning orientation toward extrinsic goals and anxiety in the assessment were the least self-regulated. It was found that students used learning strategies in a non-uniform way, there were strategies frequently used and others occasionally used. The three strategies most used were the monitoring of learning, control of the place of study and effort regulation; the strategies least used were time management and selection and organization of information. The results of this phase also allowed to propose a new hypothesis to investigate the self-regulation in the learning: the self-regulation of some aspects of the motivation and the use of some strategies depend on the subject that the students are coursing; on the contrary, other aspects of motivation and other learning strategies do not depend on the subject. Educational intervention, the third phase, consisted in offering instruction at students on summarizing technique to facilitate them to select and organize the information of engineering technical texts; in addition, students practiced the production of abstracts and the teachers provided them feedback on the quality of these abstracts. The effects of the educational intervention were explored with a quasi-experimental investigation (experimental group: 177 students, control group: 65 students) that collected quantitative and qualitative evidences. The educational intervention facilitated that students increase positive and significantly, in a statistical sense, the writing of abstracts to select and organize the information; the quality of the abstracts also significantly improved. The intervention also impacted the use of strategies such as metacognition and resource management as time management. The results of this thesis provide solutions to the current problems of the "learn to learn" competence: practical contributions such as the MSLQ-Colombia and the didactic sequence of the educational intervention, empirical contributions such as the psychometric indexes of MSLQ-Colombia, the characterization of the self-regulation in learning of students and the impacts of educational intervention. Finally, this thesis sets a new integrative approach (hypothesis) of the previous ones about the research on the self-regulation in learning.El objetivo de esta Tesis fue establecer bases para caracterizar la competencia "aprender a aprender" y potenciarla en un contexto educativo de ingeniería. Se adoptó la visión de la psicología educativa que instaura la autorregulación en el aprendizaje como la manifestación operativa de esta competencia. La investigación se desarrolló en tres fases: obtención de una herramienta psicométrica para caracterizar la autorregulación en el aprendizaje; caracterización de la autorregulación en el aprendizaje de los estudiantes; y, a partir de los resultados de la caracterización, se diseñó, implementó y evaluó una intervención educativa para facilitar a los estudiantes usar la estrategia de aprendizaje selección y organización de la información. En la primera fase para obtener la herramienta psicométrica se tradujo, adaptó y validó el Motivated Strategies for Learning Questionnaire - MSLQ siguiendo las directrices de la International Test Commission (ITC). El resultado fue el MSLQ-Colombia. Con la participación de 1218 estudiantes y 12 profesores de ingeniería se estudiaron las propiedades psicométricas del MSLQ-Colombia: validez de constructo, validez de contenido, validez externa y confiabilidad; el MSLQ-Colombia resultó válido y confiable. En la caracterización, segunda fase, se valoró la autorregulación de la motivación y el uso de estrategias de aprendizaje de 1268 estudiantes. Se encontró que los estudiantes autorregulaban altamente su motivación: las creencias de control del aprendizaje y la valoración de la tarea fueron los aspectos que más autorregularon, mientras que la orientación del aprendizaje hacia metas extrínsecas y la ansiedad en la evaluación fueron los menos autorregulados. Se halló que los estudiantes usaban estrategias de aprendizaje de manera no uniforme, hubo estrategias de uso frecuente y otras de uso ocasional. Las tres estrategias más usadas fueron el monitoreo del aprendizaje, control del lugar de estudio y regulación del esfuerzo; las menos usadas fueron la gestión del tiempo y selección y organización de la información. Los resultados de esta fase también permitieron plantear una nueva hipótesis para investigar la autorregulación en el aprendizaje: la autorregulación de algunos aspectos de la motivación y el uso de algunas estrategias dependen de la asignatura que los estudiantes están cursando; por el contrario, otros aspectos de la motivación y otras estrategias de aprendizaje no dependen de la asignatura. La intervención educativa, tercera fase, consistió en ofrecer a los estudiantes instrucción sobre la técnica de resumir para facilitarles seleccionar y organizar la información de textos técnicos de ingeniería; asimismo, los estudiantes elaboraron resúmenes y se les brindó realimentación sobre la calidad de dichos resúmenes. Los efectos de la intervención educativa se exploraron con una investigación cuasi-experimental (grupo experimental: 177 estudiantes, grupo control: 65 estudiantes) que recolectó evidencias cuantitativas y cualitativas. La intervención educativa facilitó que los estudiantes incrementaran positiva y significativamente, en sentido estadístico, la escritura de resúmenes para seleccionar y organizar la información; los estudiantes también mejoraron significativamente la calidad de los resúmenes. La intervención también impactó el uso de estrategias como la metacognición y la administración de recursos como gestión del tiempo. Los resultados de esta Tesis aportan soluciones a las problemáticas actuales de la competencia "aprender a aprender": contribuciones prácticas como el MSLQ-Colombia y la secuencia didáctica de la intervención educativa; contribuciones empíricas como los índices psicométricos del MSLQ-Colombia, la caracterización de la autorregulación del aprendizaje de los estudiantes y los impactos de la intervención educativa. Por último, esta Tesis establece un nuevo enfoque (hipótesis) integrador de los anteriores en la investigación de la autorregulación del aprendizaje

Integrated sensitive on-chip ion field effect transistors based on wrinkled InGaAs nanomembranes

Self-organized wrinkling of pre-strained nanomembranes into nanochannels is used to fabricate a fully integrated nanofluidic device for the development of ion field effect transistors (IFETs). Constrained by the structure and shape of the membrane, the deterministic wrinkling process leads to a versatile variation of channel types such as straight two-way channels, three-way branched channels, or even four-way intersection channels. The fabrication of straight channels is well controllable and offers the opportunity to integrate multiple IFET devices into a single chip. Thus, several IFETs are fabricated on a single chip using a III-V semiconductor substrate to control the ion separation and to measure the ion current of a diluted potassium chloride electrolyte solution

Sex difference and intra-operative tidal volume: Insights from the LAS VEGAS study

BACKGROUND: One key element of lung-protective ventilation is the use of a low tidal volume (VT). A sex difference in use of low tidal volume ventilation (LTVV) has been described in critically ill ICU patients.OBJECTIVES: The aim of this study was to determine whether a sex difference in use of LTVV also exists in operating room patients, and if present what factors drive this difference.DESIGN, PATIENTS AND SETTING: This is a posthoc analysis of LAS VEGAS, a 1-week worldwide observational study in adults requiring intra-operative ventilation during general anaesthesia for surgery in 146 hospitals in 29 countries.MAIN OUTCOME MEASURES: Women and men were compared with respect to use of LTVV, defined as VT of 8 ml kg-1 or less predicted bodyweight (PBW). A VT was deemed 'default' if the set VT was a round number. A mediation analysis assessed which factors may explain the sex difference in use of LTVV during intra-operative ventilation.RESULTS: This analysis includes 9864 patients, of whom 5425 (55%) were women. A default VT was often set, both in women and men; mode VT was 500 ml. Median [IQR] VT was higher in women than in men (8.6 [7.7 to 9.6] vs. 7.6 [6.8 to 8.4] ml kg-1 PBW, P < 0.001). Compared with men, women were twice as likely not to receive LTVV [68.8 vs. 36.0%; relative risk ratio 2.1 (95% CI 1.9 to 2.1), P < 0.001]. In the mediation analysis, patients' height and actual body weight (ABW) explained 81 and 18% of the sex difference in use of LTVV, respectively; it was not explained by the use of a default VT.CONCLUSION: In this worldwide cohort of patients receiving intra-operative ventilation during general anaesthesia for surgery, women received a higher VT than men during intra-operative ventilation. The risk for a female not to receive LTVV during surgery was double that of males. Height and ABW were the two mediators of the sex difference in use of LTVV.TRIAL REGISTRATION: The study was registered at Clinicaltrials.gov, NCT01601223

Rolled-up microtubes as components for Lab-on-a-Chip devices

Rolled-up nanotechnology based on strain-engineering is a powerful tool to manufacture three-dimensional hollow structures made of virtually any kind of material on a large variety of substrates. The aim of this thesis is to address the key features of different on- and off-chip applications of rolled-up microtubes through modification of their basic framework. The modification of the framework pertains to the tubular structure, in particular the diameter of the microtube, and the material which it is made of, hence achieving different functionalities of the final rolled-up structure. The tuning of the microtube diameter which is adjusted to the individual size of an object allows on-chip studies of single cells in artificial narrow cavities, for example. Another modification of the framework is the addition of a catalytic layer which turns the microtube into a self-propelled catalytic micro-engine. Furthermore, the tuneability of the diameter can have applications ranging from nanotools for drilling into cells, to cargo transporters in microfluidic channels. Especially rolled-up microtubes based on low-cost and easy to deposit materials, such as silicon oxides, can enable the exploration of novel systems for several scientific topics. The main objective of this thesis is to combine microfluidic features of rolled-up structures with optical sensor capabilities of silicon oxide microtubes acting as optical ring resonators, and to integrate these into a Lab-on-a-Chip system. Therefore, a new concept of microfluidic integration is developed in order to establish an inexpensive, reliable and reproducible fabrication process which also sustains the optical capabilities of the microtubes. These integrated microtubes act as optofluidic refractrometric sensors which detect changes in the refractive index of analytes using photoluminescence spectroscopy. The thesis concludes with a demonstration of a functional portable sensor device with several integrated optofluidic sensors.Die auf verspannten Dünnschichten basierende „rolled-up nanotechnologie“ ist eine leistungsfähige Methode um dreidimensionale hohle Strukturen (Mikroröhrchen) aus nahezu jeder Art von Material auf einer großen Vielfalt von Substraten herzustellen. Ausgehend von der Möglichkeit der Skalierung des Röhrchendurchmessers und der Modifikation der Funktionalität des Röhrchens durch Einsatz verschiedener Materialien und Oberflächenfunktionalisierungen kann eine große Anzahl an verschiedenen Anwendungen ermöglicht werden. Eine Anwendung behandelt unter anderem on-chip Studien einzelner Zellen wobei die Mikroröhrchen, an die Größe der Zelle angepasste, Reaktionscontainer darstellen. Eine weitere Modifikation der Funktionalität der Mikroröhrchen kann durch das Aufbringen einer katalytischen Schicht realisiert werden, wodurch das Mikroröhrchen zu einem selbstangetriebenen katalytischen Mikro-Motor wird. Hauptziel dieser Arbeit ist es Mikrometer große optisch aktive Glasröhrchen herzustellen, diese mikrofluidisch zu kontaktieren und als Sensoren in Lab-on-a-Chip Systeme zu integrieren. Die integrierten Glasröhrchen arbeiten als optofluidische Ringresonatoren, welche die Veränderungen des Brechungsindex von Fluiden im inneren des Röhrchens durch Änderungen im Evaneszenzfeld detektieren können. Die Funktionsfähigkeit eines Demonstrators wird mit verschiedenen Flüssigkeiten gezeigt, dabei kommt ein Fotolumineszenz Spektrometer zum Anregen des Evaneszenzfeldes und Auslesen des Signals zum Einsatz. Die entwickelte Integrationsmethode ist eine Basis für ein kostengünstiges, zuverlässiges und reproduzierbares Herstellungsverfahren von optofluidischen Mikrochips basierend auf optisch aktiven Mikroröhrchen

Dimensionality of rolled-up nanomembranes controls neural stem cell migration mechanism

We employ glass microtube structures fabricated by rolledup nanotechnology to infer the influence of scaffold dimensionality and cell confinement on neural stem cell (NSC) migration. Thereby, we observe a pronounced morphology change that marks a reversible mesenchymal to amoeboid migration mode transition. Space restrictions preset by the diameter of nanomembrane topography modify the cell shape toward characteristics found in living tissue. We demonstrate the importance of substrate dimensionality for the migration mode of NSCs and thereby define rolled-up nanomembranes as the ultimate tool for single-cell migration studies

Dimensionality of Rolled-up Nanomembranes Controls Neural Stem Cell Migration Mechanism

We employ glass microtube structures fabricated by rolled-up nanotechnology to infer the influence of scaffold dimensionality and cell confinement on neural stem cell (NSC) migration. Thereby, we observe a pronounced morphology change that marks a reversible mesenchymal to amoeboid migration mode transition. Space restrictions preset by the diameter of nanomembrane topography modify the cell shape toward characteristics found in living tissue. We demonstrate the importance of substrate dimensionality for the migration mode of NSCs and thereby define rolled-up nanomembranes as the ultimate tool for single-cell migration studies

Self-Propelled Nanotools

We describe nanoscale tools in the form of autonomous and remotely guided catalytically self-propelled InGaAs/GaAs/(Cr)Pt tubes. These rolled-up tubes with diameters in the range of 280–600 nm move in hydrogen peroxide solutions with speeds as high as 180 μm s^–1. The effective transfer of chemical energy to translational motion has allowed these tubes to perform useful tasks such as transport of cargo. Furthermore, we observed that, while cylindrically rolled-up tubes move in a straight line, asymmetrically rolled-up tubes move in a corkscrew-like trajectory, allowing these tubes to drill and embed themselves into biomaterials. Our observations suggest that shape and asymmetry can be utilized to direct the motion of catalytic nanotubes and enable mechanized functions at the nanoscale