High-resolution 3D printing enabled, minimally invasive fibre optic sensing and imaging probes

Minimally invasive surgical procedures have become more favourable to their traditional surgical counterparts due to their reduced risks, faster recovery times and decreased trauma. Despite this, there are still some limitations involved with these procedures, such as the spatial confinement of operating through small incisions and the intrinsic lack of visual or tactile feedback. Specialised tools and imaging equipment are required to overcome these issues. Providing better feedback to surgeons is a key area of research to enhance the outcomes and safety profiles of minimally invasive procedures. This thesis is centred on the development of new microfabrication methods to create novel fibre optic imaging and sensing probes that could ultimately be used for improving the guidance of minimally invasive surgeries. Several themes emerged in this process. The first theme involved the use and optimisation of high-resolution 3D injection of polymers as sacrificial layers onto which parylene-C was deposited. One outcome from this theme was a series of miniaturised parylene-C based membranes to create fibre optic pressure sensors for physiological pressure measurements and for ultrasound reception. The pressure sensor sensitivity was found to vary from 0.02 to 0.14 radians/mmHg, as the thickness of parylene was decreased from 2 to 0.5 μm. The ultrasound receivers were characterised and exhibited a noise equivalent pressure (NEP) value of ~100 Pa (an order of magnitude improvement compared to similarly sized piezoelectric hydrophones). A second theme employed high-resolution 3D printing to create microstructures of polydimethylsiloxane (PDMS) and subsequently formed nanocomposites, to create microscale acoustic hologram structures. This theme included the development of innovative manufacturing processes such as printing directly onto optical fibres, micro moulding and precise deposition which enabled the creation of such devices. These microstructures were investigated for reducing the divergence of photoacoustically-generated ultrasound beams. Taken together, the developments in this thesis pave the way for 3D microfabricated polymer-based fibre optic sensors that could find broad clinical utility in minimally invasive procedures

Design, Parameter Optimization and In Vitro Evaluation of Implantable Medical Devices

The number of implantable medical devices ranging from dental implants to cardiovascular implants has been exponentially increased in the last decades and various materials including metallic materials and polymeric materials are used in medical device manufacturing. In metallic materials, nitinol is widely used due to its superelasticity and well-known biocompatibility. Finite element modeling (FEM) along with in vitro and in vivo is being adopted to evaluate the medical device performance in patients and optimize medical designs. In this dissertation, four innovative implantable medical devices were developed and their performances were evaluated using finite element modeling and in vitro testing: 1) ventriculoamniotic shunt for aqueductal stenosis treatment. It has the conduit to drain excessive cerebrospinal fluid (CSF) to lower intracranial pressure in fetal brains and the anchors to prevent the device dislocation during the treatment. The shunt tube design was optimized using computational fluid dynamics calculations. The anchor design was determined with ANSYS Static Structural and the prototype was manufactured based on modeling results. In vitro pressure and flow rate measurement within shunt device demonstrate that the pressure in fetal brain can be reduced by 95.2% while the pressure elevation in amniotic sac is negligible. 2) TFN flow-diverter integrated with flow sensing system for cerebral aneurysm post-treatment monitoring. The flexibility of TFN membrane was investigated using both computational modeling and stretching experiment. As the TFN was wrapped on a flow-diverter backbone with junction points, we evaluated the attachment patterns between a TFN and stent backbone. Finally, micro-scale flow sensor was designed and fabricated based on the computational modeling. 3) compartmentalized stent to isolate the perfusion of the abdominal organs. The fluid dynamics inside the arterial and venous organ perfusion stent (OPS) was analyzed in terms of velocity distribution and wall shear stress (WSS). In vitro pressure difference both in arterial and venous OPS showed that the stent deployment with perfusion flow to the abdominal organs will not generate a significant load on the donor's heart. 4) retrievable stent graft for noncompressible hemorrhage control. The mechanical and biological properties of ePTFE membrane were investigated and the nitinol framed backbone was evaluated in terms of radial force

Design, characterization and validation of integrated bioelectronics for cellular studies: from inkjet-printed sensors to organic actuators

Mención Internacional en el título de doctorAdvances in bioinspired and biomimetic electronics have enabled coupling engineering devices to biological systems with unprecedented integration levels. Major efforts, however, have been devoted to interface malleable electronic devices externally to the organs and tissues. A promising alternative is embedding electronics into living tissues/organs or, turning the concept inside out, lading electronic devices with soft living matters which may accomplish remote monitoring and control of tissue’s functions from within. This endeavor may unleash the ability to engineer “living electronics” for regenerative medicine and biomedical applications. In this context, it remains a challenge to insert electronic devices efficiently with living cells in a way that there are minimal adverse reactions in the biological host while the electronics maintaining the engineered functionalities. In addition, investigating in real-time and with minimal invasion the long-term responses of biological systems that are brought in contact with such bioelectronic devices is desirable. In this work we introduce the development (design, fabrication and characterization) and validation of sensors and actuators mechanically soft and compliant to cells able to properly operate embedded into a cell culture environment, specifically of a cell line of human epithelial keratinocytes. For the development of the sensors we propose moving from conventional microtechnology approaches to techniques compatible with bioprinting in a way to support the eventual fabrication of tissues and electronic sensors in a single hybrid plataform simultaneously. For the actuators we explore the use of electroactive, organic, printing-compatible polymers to induce cellular responses as a drug-free alternative to the classic chemical route in a way to gain eventual control of biological behaviors electronically. In particular, the presented work introduces inkjet-printed interdigitated electrodes to monitor label-freely and non-invasively cellular migration, proliferation and cell-sensor adhesions of epidermal cells (HaCaT cells) using impedance spectroscopy and the effects of (dynamic) mechanical stimulation on proliferation, migration and morphology of keratinocytes by varying the magnitude, frequency and duration of mechanical stimuli exploiting the developed biocompatible actuator. The results of this thesis contribute to the envision of three-dimensional laboratory-growth tissues with built-in electronics, paving exciting avenues towards the idea of living smart cyborg-skin substitutes.En los útimos años los avances en el desarrollo de dispositivos electrónicos diseñados imitando las propiedades de sistemas vivos han logrado acoplar sistemas electrónicos y órganos/tejidos biológicos con un nivel de integración sin precedentes. Convencionalmente, la forma en que estos sistemas bioelectrónicos son integrados con órganos o tejidos ha sido a través del contacto superficial entre ambos sistemas, es decir acoplando la electrónica externamente al tejido. Lamentablemente estas aproximaciones no contemplan escenarios donde ha habido una pérdida o daño del tejido con el cual interactuar, como es el caso de daños en la piel debido a quemaduras, úlceras u otras lesiones genéticas o producidas. Una alternativa prometedora para ingeniería de tejidos y medicina regenerativa, y en particular para implantes de piel, es embeber la electrónica dentro del tejido, o presentado de otra manera, cargar el sistema electrónico con células vivas y tejidos fabricados por ingeniería de tejidos como parte innata del propio dispositivo. Este concepto permitiría no solo una monitorización remota y un control basado en señalizaciones eléctricas (sin químicos) de tejidos biológicos fabricados mediante técnicas de bioingeniería desde dentro del propio tejido, sino también la fabricación de una “electrónica viva”, biológica y eléctricamente funcional. En este contexto, es un desafío insertar de manera eficiente dispositivos electrónicos con células vivas sin desencadenar reacciones adversas en el sistema biológico receptor ni en el sistema electrónico diseñado. Además, es deseable monitorizar en tiempo real y de manera mínimamente invasiva las respuestas de dichos sistemas biológicos que se han añadido a tales dispositivos bioelectrónicos. En este trabajo presentamos el desarrollo (diseño, fabricación y caracterización) y validación de sensores y actuadores mecánicamente suaves y compatibles con células capaces de funcionar correctamente dentro de un entorno de cultivo celular, específicamente de una línea celular de células epiteliales humanas. Para el desarrollo de los sensores hemos propuesto utilizar técnicas compatibles con la bioimpresión, alejándonos de la micro fabricación tradicionalmente usada para la manufactura de sensores electrónicos, con el objetivo a largo plazo de promover la fabricación de los tejidos y los sensores electrónicos simultáneamente en un mismo sistema de impresión híbrido. Para el desarrollo de los actuadores hemos explorado el uso de polímeros electroactivos y compatibles con impresión y hemos investigado el efecto de estímulos mecánicos dinámicos en respuestas celulares con el objetivo a largo plazo de autoinducir comportamientos biológicos controlados de forma electrónica. En concreto, este trabajo presenta sensores basados en electrodos interdigitados impresos por inyección de tinta para monitorear la migración celular, proliferación y adhesiones célula-sustrato de una línea celular de células epiteliales humanas (HaCaT) en tiempo real y de manera no invasiva mediante espectroscopía de impedancia. Por otro lado, este trabajo presenta actuadores biocompatibles basados en el polímero piezoeléctrico fluoruro de poli vinilideno y ha investigado los efectos de estimular mecánicamente células epiteliales en relación con la proliferación, migración y morfología celular mediante variaciones dinámicas de la magnitud, frecuencia y duración de estímulos mecánicos explotando el actuador biocompatible propuesto. Ambos sistemas presentados como resultado de esta tesis doctoral contribuyen al desarrollo de tejidos 3D con electrónica incorporada, promoviendo una investigación hacia la fabricación de sustitutos equivalentes de piel mitad orgánica mitad electrónica como tejidos funcionales biónicos inteligentes.The main works presented in this thesis have been conducted in the facilities of the Universidad Carlos III de Madrid with support from the program Formación del Profesorado Universitario FPU015/06208 granted by Spanish Ministry of Education, Culture and Sports. Some of the work has been also developed in the facilities of the Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration (IZM) and University of Applied Sciences (HTW) in Berlin, under the supervision of Prof. Dr. Ing. H-D. Ngo during a research visit funded by the Mobility Fellows Program by the Spanish Ministry of Education, Culture, and Sports. This work has been developed in the framework of the projects BIOPIELTEC-CM (P2018/BAA-4480), funded by Comunidad de Madrid, and PARAQUA (TEC2017-86271-R) funded by Ministerio de Ciencia e Innovación.Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidente: José Antonio García Souto.- Secretario: Carlos Elvira Pujalte.- Vocal: María Dimak

Technology 2003: Conference Proceedings from the Fourth National Technology Transfer Conference and Exposition, Volume 1

Proceedings from symposia of the Technology 2003 Conference and Exposition, December 7-9, I993, Anaheim, CA. Volume 1 features the Plenary Session and the Plenary Workshop, plus papers presented in Advanced Manufacturing, Biotechnology/Medical Technology, Environmental Technology, Materials Science, and Power and Energy

A versatile platform for three-dimensional dynamic suspension culture applications

In the last decades, the rapid upgrading in cell biological knowledge has bumped the interest in using cell-based therapeutic approaches as well as cell-based model systems for the treatment of diseases. Given the rapid translation towards cell-based clinical treatments and the consequent increasing demand of cell sources, three-dimensional (3D) suspension cultures have demonstrated to be an advantageous alternative to monolayer techniques for large scale expansion of cells and for the generation of three-dimensional model systems in a scale-up perspective. In this scenario, a versatile bioreactor platform suitable for 3D dynamic suspension cell culture under tuneable shear stress conditions is developed and preliminarily tested in two different biotechnological applications. By adopting simple technological solutions and avoiding rotating components, the bioreactor exploits a laminar hydrodynamics, enabling dynamic cell suspension in an environment favourable to mass transport. Technically, the bioreactor is conceived to produce dynamic suspension cell culture under tuneable shear stress conditions without the use of moving components (from ultralow to moderate shear stress). A multiphysics computational modelling strategy is applied for the development and optimization of the suspension bioreactor platform. The in silico modelling is used to support the design and optimization phase of the bioreactor platform, providing a comprehensive analysis of its operating principles, also supporting the development/optimization of culture protocols directly in silico, and thus minimizing preliminary laboratory tests. After the technical assessment of the functionality of the device and a massive number of in silico simulations for its characterization, the bioreactor platform has been employed for two preliminary experimental applications, in order to determine the suitability of the device for culturing human cells under dynamic suspension. In detail, the bioreactor platform has been used to culture lung cancer cells for spheroid formation (Calu-3 cell line) under ultralow shear stress conditions, and for human induced pluripotent stem cell (hiPSC) dynamic suspension culture. The use of the bioreactor platform for the formation of cancer cell spheroids under low shear stress conditions confirms the suitability of the device for its use as dynamic suspension bioreactor. In fact, compared to static cell suspension, after 5 days of dynamic suspension culture the bioreactor platform preserves morphological features, promotes intercellular connection, increases the number of cycling cells, and reduces double strand DNA damage. Calu-3 cells form functional 3D spheroids characterized by more functional adherence junctions between cells. Moreover, the computational model has been used as a tool for assisting the setup of the experimental framework with the extraction of the fluid dynamic features establishing inside the bioreactor culture chamber. As second proof of concept application, the bioreactor platform has been tested for the dynamic suspension of hiPSCs. Starting from the ‘a priori’ knowledge gained by the development of the in silico culture protocol, the agglomeration of human induced pluripotent stem cells has been modulated by means of the combination of moderate intermittent shear stress and free-fall transport within the bioreactor culture chamber. The inoculation of single cells suspensions inside the bioreactor chamber promotes cell-cell interaction and consequently the formation of human induced pluripotent stem cell aggregates. In conclusion, the impeller-free functioning principle characterizing the proposed bioreactor platform demonstrates to be promising for human cell dynamic suspension culture. In the future, this bioreactor platform will be further optimized for the realization of impeller-free dynamic suspension bioreactors dedicated and optimized to specific applications in stem cell and cancer cell culture

Industrial-Scale Manufacture of Oleosin 30G for Use as Contrast Agent in Echocardiography

In ultrasound sonography, microbubbles are used as contrasting agents to improve the effectiveness of ultrasound imaging. Monodisperse microbubbles are required to achieve the optimal image quality. In order to achieve a uniform size distribution, microbubbles are stabilized with surfactant molecules. One such molecule is Oleosin, an amphiphilic structural protein found in vascular plant oil bodies that contains one hydrophobic and two hydrophilic sections. Controlling the functionalization of microbubbles is a comprehensive and versatile process using recombinant technology to produce a genetically engineered form of Oleosin called Oleosin 30G. With the control of a microfluidic device, uniformly-sized and resonant microbubbles can be readily produced and stored in stable conditions up to one month. Currently, Oleosin microbubbles are limited to the lab-scale; however, through development of an integrated batch bioprocessing model, the overall product yield of Oleosin 30G can be increased to 7.39 kg/year to meet needs on the industrial-scale. An Oleosin-stabilized microbubble suspension as a contrast agent is in a strong position to take a competitive share of the current market, capitalizing on needs unmet by current market leader, Definity®. Based on market dynamics and process logistics, scaled-up production of Oleosin 30G for use as a contrast agent is expected to be both a useful and profitable venture

Thin-Layer Prestressed Composite Ferroelectric Driver and Sensor Characterization with Application to Separation Flow Control

Experiments were conducted in two different stages--general piezoelectric actuator characterization and flow separation control applications. The characterization of the piezoelectric devices was performed in several stages, due to the many variables that affect performance. The first stage of the characterization consisted of tests conducted on 13 different THUNDERTM (thin-layer composite unimorph ferroelectric driver and sensor) configurations. These configurations consisted of a combination of 1, 3, 5, 7, and 9 layers of 25μ thick aluminum as backing material, with and without a top layer of 25μ aluminum. All of these configurations used the same piezoelectric ceramic wafer (PZT-5A) with dimensions of 5.1 x 3.8 x 0.018 cm. The above configurations were tested at two stages of the manufacturing process: before and after re-poling. The parameters measured included frequency, driving voltage, displacement, capacitance, and radius of curvature. An optical sensor recorded the displacement at a fixed voltage (100-400 Vpp) over a predetermined frequency range (1-1000 Hz). These displacement measurements were performed using a computer that controlled the process of activating and measuring the displacement of the device. A parameter was defined which can be used to predict which configuration will produce maximum displacement for a partially constrained device. The second phase of the characterization was conducted using two different types of piezoelectric devices. Actuators were made with PZT wafers of 3.8 x 1.9 x 0.025cm, and 3.8 x 1.3 x 0.02 cm. These models consisted of a combination of top layers of 1 mil (0.0254 mm) aluminum and brass, and bottom layers of stainless steel, aluminum, and brass of varying thickness (3, 4, 5, 7, 9, 10 mil (0.076, 0.102, 0.127, 0.178, 0.229, 0.254 mm)). Displacement was measured for 12 configurations at 1 Hz and 200 Vpp under loads of 0, 0.2, 0.4, 0.5, and 1.0 Kg using an optical sensor. Again the parameter β was used to predict the configuration with the maximum displacement for a partially constrained device, as well as with the device under load. Finally, a THUNDERTM based actuator was used to deploy submerged vane-type vortex generators which were used to control turbulent separated flow associated with flow over a backward-facing ramp. Effectiveness of the vortex generator array was demonstrated using wall pressure measurements, velocity surveys, and smoke-oil flow visualization photographs which showed that the nominal flow separation region was reduced by 35-40%

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community