Soft Materials for Wearable/Flexible Electrochemical Energy Conversion, Storage, and Biosensor Devices

none6Next-generation wearable technology needs portable flexible energy storage, conversion, and biosensor devices that can be worn on soft and curved surfaces. The conformal integration of these devices requires the use of soft, flexible, light materials, and substrates with similar mechanical properties as well as high performances. In this review, we have collected and discussed the remarkable research contributions of recent years, focusing the attention on the development and arrangement of soft and flexible materials (electrodes, electrolytes, substrates) that allowed traditional power sources and sensors to become viable and compatible with wearable electronics, preserving or improving their conventional performances.openBocchetta, P.; Frattini, D.; Ghosh, S.; Mohan, A.M.V.; Kumar, Y.; Kwon, Y.Bocchetta, P.; Frattini, D.; Ghosh, S.; Mohan, A. M. V.; Kumar, Y.; Kwon, Y

Nanomaterials-Based Bioinspired Next Generation Wearable Sensors: A State-of-the-Art Review

With a constantly growing percentage of the population having access to high-quality healthcare facilities, preventable pathogenic illnesses have been nearly eradicated in the developed parts of the world, which has led to a significant rise in the average human life expectancy over the last few decades. In such a highly developed world, age-related illnesses will lead to an immense burden on healthcare providers. Remote health monitoring enabled by wearable sensors will play a significant role in the growth and evolution of Health 3.0 by providing intimate and valuable information to healthcare providers regarding the progression of disease in patients with critical life-altering conditions. Especially, in the case of people suffering from neurodegenerative disorders, inexpensive and user-friendly wearable sensors can enable physiotherapists monitor real-time physiological parameters to design patient-specific treatment plans. This review provides a comprehensive overview of the recent advances and emerging trends at the convergence of biomimicry and nanomaterial sensors, with a specific focus on wearable skin-inspired mechanical sensors for applications in IoT-enabled human physiological parameters monitoring. Skin-inspired wearable mechanical sensors with relevance to the most common types of sensing mechanisms including piezoresistive, piezocapacitive, and triboelectric sensing are discussed along with their current challenges and possible future opportunities

Nanomaterials-Based Bioinspired Next Generation Wearable Sensors: A State-of-the-Art Review

With a constantly growing percentage of the population having access to high-quality healthcare facilities, preventable pathogenic illnesses have been nearly eradicated in the developed parts of the world, which has led to a significant rise in the average human life expectancy over the last few decades. In such a highly developed world, age-related illnesses will lead to an immense burden on healthcare providers. Remote health monitoring enabled by wearable sensors will play a significant role in the growth and evolution of Health 3.0 by providing intimate and valuable information to healthcare providers regarding the progression of disease in patients with critical life-altering conditions. Especially, in the case of people suffering from neurodegenerative disorders, inexpensive and user-friendly wearable sensors can enable physiotherapists monitor real-time physiological parameters to design patient-specific treatment plans. This review provides a comprehensive overview of the recent advances and emerging trends at the convergence of biomimicry and nanomaterial sensors, with a specific focus on wearable skin-inspired mechanical sensors for applications in IoT-enabled human physiological parameters monitoring. Skin-inspired wearable mechanical sensors with relevance to the most common types of sensing mechanisms including piezoresistive, piezocapacitive, and triboelectric sensing are discussed along with their current challenges and possible future opportunities

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

Transient electronics: Materials, mechanics, and applications

Transient electronics is an emerging field in materials science that has attracted considerable attention from the scholar community in the last few years. The unique attribute of transient technology is the capability to fully or partially disintegrate after a predefined period of stable operation. Transient electronics have a wide range of potential applications as biomedical implants, environmental sensors, and hardware-secured devices. Biodegradable transient sensors could be dissolved and absorbed into a bio-environment, eliminating complications associated with long-term presence of implanted devices, or secondary surgery to extract implanted devices. Eco-friendly environmental monitoring transient devices could be utilized to collect desired data, then degrade naturally into the surrounding environment, reducing the recollection expenses, and minimizing harmful waste. Self-deconstructing platforms could undergo disintegration and physically remove sensitive information once transience is triggered. Recent developments on transient materials, dissolution/disintegration mechanisms, manufacturing techniques, structural designs, and transient energy storage devices have advanced the functionality, performance, and applicability of transient electronics. Further research on precisely controlled transiency, however, is needed to broaden the applications of transient electronics. Since transient electronics are typically multilayer thin-film structures, to achieve controlled transiency at device level, it is crucial to understand the interfacial interactions among layers of dissimilar materials assembled on one another to form complex transient devices. This dissertation discusses materials, transiency mechanisms, and applications of transient electronics. Firstly, interfacial interactions among layers of dissimilar materials is systematically studied, revealing the mechanism of transiency achieved by swelling induced disintegration. Following section reports a transient battery utilizing swelling induced transiency as a proof-of-concept application. Lastly, the dissertation presents materials, mechanical properties, and applications of all-organic soft transient electronics. Firstly, to understand the underlying mechanism of swelling induced transiency, we studied interfacial interactions of a particular case of polymeric substrate with lithium titanate electrode coating layer. The structure is analogous to that of the anode in typical lithium-ion batteries; yet, can be extended to more general cases of soft electronics. This coordinated experimental-analytical-simulation study exhibited formation, accumulation and propagation of swelling-induced stress and fracture through the membrane-coating interface, when in transient mode. Swelling-induced stress as a function of electrode thickness was studied; the analytical data and simulations were verified by experimental results. Moreover, the fragment size of the electrode coating layer as a function of initial defect prevalence and distribution was investigated. The average fragment size was predicted using a combination of experimentally-determined initial defect distribution and finite element method-obtained swelling strain – defect length curve. The predicted average fragment size was found to be in good agreement with the experimental results. Meanwhile, as an application of swelling induced transiency, a transient lithium-ion battery based on polymeric constituents is presented. The battery takes advantage of a close variation of the active materials used in conventional lithium-ion batteries and can achieve and maintain a potential of \u3e 2.5 V. All materials are deposited form polymer-based emulsions and the transiency is achieved through a hybrid approach of redispersion of insoluble, and dissolution of soluble components in approximately 30 minutes. The reported transient battery could be applied an onboard power for transient electronics. In addition, a flexible all-organic transient sensor with potential to be applied as epidermal sensor is reported. A conductive conjugated polymer electrode was printed onto a water-soluble polymer substrate with an electrodehydrodynamic jetting printer. The all-organic electrode is partially transient with supportive substrate dissolved completely in water, while the conjugated polymer electrode remains intact. The intact functional electrode layer formed conformal contact with human skin and was applied as an epidermal strain sensor

Multitasking smart hydrogels based on the combination of alginate and poly(3,4-ethylenedioxythiophene) properties: A review

Poly(3,4-ethylenedioxythiophene) (PEDOT), a very stable and biocompatible conducting polymer, and alginate (Alg), a natural water-soluble polysaccharide mainly found in the cell wall of various species of brown algae, exhibit very different but at the same complementary properties. In the last few years, the remarkable capacity of Alg to form hydrogels and the electro-responsive properties of PEDOT have been combined to form not only layered composites (PEDOT-Alg) but also interpenetrated multi-responsive PEDOT/Alg hydrogels. These materials have been found to display outstanding properties, such as electrical conductivity, piezoelectricity, biocompatibility, self-healing and re-usability properties, pH and thermoelectric responsiveness, among others. Consequently, a wide number of applications are being proposed for PEDOT-Alg composites and, especially, PEDOT/Alg hydrogels, which should be considered as a new kind of hybrid material because of the very different chemical nature of the two polymeric components. This review summarizes the applications of PEDOT-Alg and PEDOT/Alg in tissue interfaces and regeneration, drug delivery, sensors, microfluidics, energy storage and evaporators for desalination. Special attention has been given to the discussion of multi-tasking applications, while the new challenges to be tackled based on aspects not yet considered in either of the two polymers have also been highlighted.Peer ReviewedPostprint (published version

Shapeable magnetoelectronics

Inorganic nanomembranes are shapeable (flexible, printable, and even stretchable) and transferrable to virtually any substrate. These properties build the core concept for new technologies, which transform otherwise rigid high-speed devices into their shapeable counterparts. This research is motivated by the eagerness of consumer electronics towards being thin, lightweight, flexible, and even wearable. The realization of this concept requires all building blocks as we know them from rigid electronics (e.g., active elements, optoelectronics, magnetoelectronics, and energy storage) to be replicated in the form of (multi)functional nanomembranes, which can be reshaped on demand after fabrication. There are already a variety of shapeable devices commercially available, i.e., electronic displays, energy storage elements, and integrated circuitry, to name a few. From the beginning, the main focus was on the fabrication of shapeable high-speed electronics and optoelectronics. Only very recently, a new member featuring magnetic functionalities was added to the family of shapeable electronics. With their unique mechanical properties, the shapeable magnetic field sensor elements readily conform to ubiquitous objects of arbitrary shapes including the human skin. This feature leads electronic skin systems beyond imitating the characteristics of its natural archetype and extends their cognition to static and dynamic magnetic fields that by no means can be perceived by human beings naturally. Various application fields of shapeable magnetoelectronics are proposed. The developed sensor platform can equip soft electronic systems with navigation, orientation, motion tracking, and touchless control capabilities. A variety of novel technologies, such as smart textiles, soft robotics and actuators, active medical implants, and soft consumer electronics, will benefit from these new magnetic functionalities. This review reflects the establishment of shapeable magnetic sensorics, describing the entire development from the first attempts to verify the functional concept to the realization of ready-to-use highly compliant and strain invariant sensor devices with remarkable robustness