Wearable Electromechanical Sensors and Its Applications

Wearable electromechanical sensor transforms mechanical stimulus into electrical signals. The main electromechanical sensors we focus on are strain and pressure sensors, which correspond to two main mechanical stimuli. According to their mechanisms, resistive and capacitive sensor attracts more attentions due to their simple structures, mechanisms, preparation method, and low cost. Various kinds of nanomaterials have been developed to fabricate them, including carbon nanomaterials, metallic, and conductive polymers. They have great potentials on health monitoring, human motion monitoring, speech recognition, and related human-machine interface applications. Here, we discuss their sensing mechanisms and fabrication methods and introduce recent progress on their performances and applications

High deformation multifunctional composites: materials, processes, and applications

Structural health monitoring (SHM) is a non-destructive process of collecting and analysing data from structures to evaluate their conditions and predict the remaining lifetime. Multifunctional sensors are increasingly used in smart structures to self-sense and monitor the damages through the measurements of electrical resistivity of composites materials. Polymer-based sensors possess exceptional properties for SHM applications, such as low cost and simple processing, durability, flexibility and excellent piezoresistive sensitivity. Thermoplastic, thermoplastic elastomers and elastomer matrices can be combined with conductive nanofillers to develop piezoresistive sensors. Polymer, reinforcement fillers, processing and design have critical influences in the overall properties of the composite sensors. Together with the properties of the functional composites, environmental concerns are being increasingly relevant for applications, involving advances in materials selection and manufacturing technologies, In this scenario, additive manufacturing is playing an increasing role in modern technological solutions. Stretchable multifunctional composites applications include piezoresistive, dielectric elastomers (mainly for actuators), thermoelectric, or magnetorheological materials [1]. In the following, piezoresistive materials and applications will be mainly addressed based on their increasing implementation into applications.Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and UID/EMS/00151/2019. The authors thank the FCT for financial support under SFRH/BPD/110914/2015 (P. C) and SFRH/BPD/117838/2016 (J. Pereira) grants. Financial support from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06

Advances in test and measurement of the interface adhesion and bond strengths in coating-substrate systems, emphasising blister and bulk techniques

In this paper, recent advances in the minimum-destructive testing of the adhesion of coating-substrate systems are reviewed, focusing on key techniques such as micro- and nano-scale levels of indentation, scratching, laser-induced wave shock, as well as the blister and buckle approach. Along with adhesion failure tests, the latest and most extensive applications of the adhesion test methods in nano-, micro- and bulk-coating technology and the associated techniques to determine the minimum damage defects left on the coatings are discussed and their use reviewed

SENSING MECHANISM AND APPLICATION OF MECHANICAL STRAIN SENSOR: A MINI-REVIEW

This study reviews the potential of flexible strain sensors based on nanomaterials such as carbon nanotubes (CNTs), graphene, and metal nanowires (NWs). These nanomaterials have excellent flexibility, conductivity, and mechanical properties, which enable them to be integrated into clothing or attached to the skin for the real-time monitoring of various activities. However, the main challenge is balancing high stretchability and sensitivity. This paper explains the basic concept of strain sensors that can convert mechanical deformation into electrical signals. Moreover, this paper focuses on simple, flexible, and stretchable resistive and capacitive sensors. It also discusses the important factors in choosing materials and fabrication methods, emphasizing the crucial role of suitable polymers in high-performance strain sensing. This study reviews the fabrication processes, mechanisms, performance, and applications of stretchable strain sensors in detail. It analyzes key aspects, such as sensitivity, stretchability, linearity, response time, and durability. This review provides useful insights into the current status and prospects of stretchable strain sensors in wearable technology and human–machine interfaces

White paper on the future of plasma science and technology in plastics and textiles

This is the peer reviewed version of the following article: “Uros, C., Walsh, J., Cernák, M., Labay, C., Canal, J.M., Canal, C. (2019) White paper on the future of plasma science and technology in plastics and textiles. Plasma processes and polymers, 16 1 which has been published in final form at [doi: 10.1002/ppap.201700228]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."This white paper considers the future of plasma science and technology related to the manufacturing and modifications of plastics and textiles, summarizing existing efforts and the current state‐of‐art for major topics related to plasma processing techniques. It draws on the frontier of plasma technologies in order to see beyond and identify the grand challenges which we face in the following 5–10 years. To progress and move the frontier forward, the paper highlights the major enabling technologies and topics related to the design of surfaces, coatings and materials with non‐equilibrium plasmas. The aim is to progress the field of plastics and textile production using advanced plasma processing as the key enabling technology which is environmentally friendly, cost efficient, and offers high‐speed processingPeer ReviewedPostprint (author's final draft

Rational Design of Flexible and Stretchable Electronics based on 3D Printing

Flexible and stretchable electronics have been considered as the key component for the next generation of flexible devices. There are many approaches to prepare the devices, such as dip coating, spin coating, Mayer bar coating, filtration and transfer, and printing, etc. The effectiveness of these methods has been proven, but some drawbacks cannot be ignored, such as lacking pattern control, labor consuming, requiring complex pretreatment, wasting conductive materials, etc. In this investigation, we propose to adopt 3D printing technology to design flexible and stretchable electronics. The objective is to rationally design flexible and stretchable sensors, simplify the preparation process, form the sample with the complex desirable patterns, and promote the performance of the samples. The dissertation comprises of three major parts: water-induced polymer swelling and its application in soft electronics, utilizing 3D printing to transfer conductive layer into elastomer for building soft electronics, and 3D printing of functional devices. In the first part, we developed the soft electronics with wrinkled structure via 3D printing and water-induced polymer swelling, which can avoid some disadvantages in conventional method, e.g., pre-stretching and organic solvent-induced polymer swelling, including mechanical loss, negative effect to human health, and unidirectionally response to external deformation. Water-induced polymer swelling was achieved by introducing soluble particles into silicone matrixes and soaking the polymer composites in aqueous solution. We have investigated the characteristics and mechanisms of water-induced polymer swelling. Then, the conductive materials were deposited on the swollen sample to form the desired wrinkled structures for stretchable sensors. Furthermore, a dopamine layer was adopted to enhance the adhesion of matrix and conductive layer. The improvement was a key enabler to achieve superior electrical properties of 3D printed stretchable sensors for long-term cyclic stretching. We have demonstrated a series of human motion detection by using these stretchable strain sensors. Another part is designing flexible electrodes with desirable complex pattern by transferring a conductive layer into soft substrates during a 3D printing process. Taking advantage of extrusion pressure and polymer adhesion, the thin conductive layers were embedded into the printed polymer patterns, which can achieve conductive flexible electronics with desirable complex patterns. High-quality transfer has been achieved through adjusting conductive layer thickness, nozzle-to-substrate distance, and printing parameters, etc. Moreover, various printing patterns were created, and their properties were exhibited. The stretchable sensors showed an outstanding stress-strain relationship and electrical response to external deformations. The third part is about 3D printing of functional devices. In the collaborated study, the drug particles were introduced into silicone matrix to prepare the drug-eluting devices. When water molecules transported into the silicone matrix, the loaded drug particles decomposed and released nitric oxide (NO) enabling antibacterial properties. It is noted that 3D printing is creatively employed to form the desirable patterns. We also observed a self-wiring effect in the printing process, i.e., the printed device is covered by a drug-free layer due to the diffusion of a low viscosity silicone component during printing, which can be utilized to prevent drug release bursts and to form a gradient drug-loaded device. The printed samples showed a sustainable NO release and good antibacterial property. Furthermore, the water-induced polymer swelling was possible to be used as actuator in humidity environment. There are some highlights deserving emphasis in the dissertation. Firstly, the water-induced polymer swelling is proposed to develop the flexible and stretchable electronics. The findings have a wide potential application. Additionally, a drug-eluting polymer device with a drug-loaded bulk and a drug-free coating is prepared via leveraging self-wiring effect in 3D printing. The structure can regulate the drug release rate. On the other hand, the additive manufacturing platform offers unique opportunities to produce drug-eluting silicone devices in a customized manner. Finally, 3D printing is employed to encapsulate the conductive layers to achieve the flexible electronics with patterned structure and high performances. The facile and effective approach provides a distinctive view in advancing the development of stretchable electronics

Excellentia Eminentia Effectio

"In these pages you will learn about the fascinating research endeavors that each of our faculty members is undertaking. We have divided their research into the broad categories of health, sustainability, information, and systems. While we recognize the imperfect nature of categorizing research that, by its very nature may be interdisciplinary or transdisciplinary, we nonetheless believe it will be helpful as a way to see the depth and breadth of our research endeavors within each grouping. As you read the profiles on these pages, I know you will begin to appreciate that, taken as a whole, the research spectrum at Columbia Engineering is exceptional and that, as our professors go about their work, they are at the cusp of making breakthroughs that will have a major impact on the way we live our lives today and tomorrow.

Recent Advancements in Graphene Derivative-Based Nanocomposites: Innovations in Coating and Sensing Technologies

Graphene derivative-based nanocomposites have emerged as innovative solutions to address challenges in corrosion, marine biofouling, and environmental contamination. This review highlights recent advancements in three key areas: (1) dual-barrier and self-healing anti-corrosion materials, (2) eco-friendly anti-biofouling coatings, and (3) high-efficiency electrocatalytic films for electrochemical sensing. We emphasize the critical roles of graphene (Gr) sheets, graphene oxide (GO), and reduced graphene oxide (rGO) in enhancing nanocomposite performance through novel modifications with inorganic materials, organic polymers, and biomolecules. Key insights into advanced modification techniques and their impact on functionality and durability are presented. The review also explores graphene-enabled electrochemical sensors that showed high sensitivity to phenolic compounds in water. Mechanisms accounting for the improved performance of these materials are discussed, along with associated challenges such as scalability, cost-effectiveness, and stability. Future directions are suggested, focusing on sustainable, intelligent coatings and thin-film devices for environmental applications. This work aims to guide researchers, industry professionals, and policymakers in leveraging graphene-based technologies to tackle global issues in corrosion prevention, marine ecology, and environmental monitoring