Inkjet-printed conductive patterns for physical manipulation of audio signals

In this demo paper, we present the realization of a completely aesthetically driven conductive image as a multi-modal music controller. Combining two emerging technologies - rapid prototyping with an off-the-shelf inkjet printer using conductive ink and parametric graphic design, we are able to create an interactive surface that is thin, flat, and flexible. This sensate surface can be conformally wrapped around a simple curved surface, and unlike touch screens, can accommodate complex structures and shapes such as holes on a surface. We present the design and manufacturing flow and discuss the technology behind this multi-modal sensing design. Our work seeks to offer a new dimension of designing sonic interaction with graphic tools, playing and learning music from a visual perspective and performing with expressive physical manipulation

PrintSense: a versatile sensing technique to support multimodal flexible surface interaction

We present a multimodal on-surface and near-surface sensing technique for planar, curved and flexible surfaces. Our technique leverages temporal multiplexing of signals coming from a universal interdigitated electrode design, which is printed as a single conductive layer on a flexible substrate. It supports sensing of touch and proximity input, and moreover is capable of capturing several levels of pressure and flexing. We leverage recent developments in conductive inkjet printing as a way to prototype electrode patterns, and combine this with our hardware module for supporting the full range of sensing methods. As the technique is low-cost and easy to implement, it is particularly well-suited for prototyping touch- and hover-based user interfaces, including curved and deformable ones

New generation of interactive platforms based on novel printed smart materials

Programa doutoral em Engenharia Eletrónica e de Computadores (área de Instrumentação e Microssistemas Eletrónicos)The last decade was marked by the computer-paradigm changing with other digital devices suddenly becoming available to the general public, such as tablets and smartphones. A shift in perspective from computer to materials as the centerpiece of digital interaction is leading to a diversification of interaction contexts, objects and applications, recurring to intuitive commands and dynamic content that can proportionate more interesting and satisfying experiences. In parallel, polymer-based sensors and actuators, and their integration in different substrates or devices is an area of increasing scientific and technological interest, which current state of the art starts to permit the use of smart sensors and actuators embodied within the objects seamlessly. Electronics is no longer a rigid board with plenty of chips. New technological advances and perspectives now turned into printed electronics in polymers, textiles or paper. We are assisting to the actual scaling down of computational power into everyday use objects, a fusion of the computer with the material. Interactivity is being transposed to objects erstwhile inanimate. In this work, strain and deformation sensors and actuators were developed recurring to functional polymer composites with metallic and carbonaceous nanoparticles (NPs) inks, leading to capacitive, piezoresistive and piezoelectric effects, envisioning the creation of tangible user interfaces (TUIs). Based on smart polymer substrates such as polyvinylidene fluoride (PVDF) or polyethylene terephthalate (PET), among others, prototypes were prepared using piezoelectric and dielectric technologies. Piezoresistive prototypes were prepared with resistive inks and restive functional polymers. Materials were printed by screen printing, inkjet printing and doctor blade coating. Finally, a case study of the integration of the different materials and technologies developed is presented in a book-form factor.A última década foi marcada por uma alteração do paradigma de computador pelo súbito aparecimento dos tablets e smartphones para o público geral. A alteração de perspetiva do computador para os materiais como parte central de interação digital levou a uma diversificação dos contextos de interação, objetos e aplicações, recorrendo a comandos intuitivos e conteúdos dinâmicos capazes de tornarem a experiência mais interessante e satisfatória. Em simultâneo, sensores e atuadores de base polimérica, e a sua integração em diferentes substratos ou dispositivos é uma área de crescente interesse científico e tecnológico, e o atual estado da arte começa a permitir o uso de sensores e atuadores inteligentes perfeitamente integrados nos objetos. Eletrónica já não é sinónimo de placas rígidas cheias de componentes. Novas perspetivas e avanços tecnológicos transformaram-se em eletrónica impressa em polímeros, têxteis ou papel. Neste momento estamos a assistir à redução da computação a objetos do dia a dia, uma fusão do computador com a matéria. A interatividade está a ser transposta para objetos outrora inanimados. Neste trabalho foram desenvolvidos atuadores e sensores e de pressão e de deformação com recurso a compostos poliméricos funcionais com tintas com nanopartículas (NPs) metálicas ou de base carbónica, recorrendo aos efeitos capacitivo, piezoresistivo e piezoelétrico, com vista à criação de interfaces de usuário tangíveis (TUIs). Usando substratos poliméricos inteligentes tais como fluoreto de polivinilideno (PVDF) ou politereftalato de etileno (PET), entre outos, foi possível a preparação de protótipos de tecnologia piezoelétrica ou dielétrica. Os protótipos de tecnologia piezoresistiva foram feitos com tintas resistivas e polímeros funcionais resistivos. Os materiais foram impressos por serigrafia, jato de tinta, impressão por aerossol e revestimento de lâmina doctor blade. Para terminar, é apresentado um caso de estudo da integração dos diferentes materiais e tecnologias desenvolvidos sob o formato de um livro.This project was supported by FCT – Fundação para a Ciência e a Tecnologia, within the doctorate grant with reference SFRH/BD/110622/2015, by POCH – Programa Operacional Capital Humano, and by EU – European Union

Digital fabrication of custom interactive objects with rich materials

As ubiquitous computing is becoming reality, people interact with an increasing number of computer interfaces embedded in physical objects. Today, interaction with those objects largely relies on integrated touchscreens. In contrast, humans are capable of rich interaction with physical objects and their materials through sensory feedback and dexterous manipulation skills. However, developing physical user interfaces that offer versatile interaction and leverage these capabilities is challenging. It requires novel technologies for prototyping interfaces with custom interactivity that support rich materials of everyday objects. Moreover, such technologies need to be accessible to empower a wide audience of researchers, makers, and users. This thesis investigates digital fabrication as a key technology to address these challenges. It contributes four novel design and fabrication approaches for interactive objects with rich materials. The contributions enable easy, accessible, and versatile design and fabrication of interactive objects with custom stretchability, input and output on complex geometries and diverse materials, tactile output on 3D-object geometries, and capabilities of changing their shape and material properties. Together, the contributions of this thesis advance the fields of digital fabrication, rapid prototyping, and ubiquitous computing towards the bigger goal of exploring interactive objects with rich materials as a new generation of physical interfaces.Computer werden zunehmend in Geräten integriert, mit welchen Menschen im Alltag interagieren. Heutzutage basiert diese Interaktion weitgehend auf Touchscreens. Im Kontrast dazu steht die reichhaltige Interaktion mit physischen Objekten und Materialien durch sensorisches Feedback und geschickte Manipulation. Interfaces zu entwerfen, die diese Fähigkeiten nutzen, ist allerdings problematisch. Hierfür sind Technologien zum Prototyping neuer Interfaces mit benutzerdefinierter Interaktivität und Kompatibilität mit vielfältigen Materialien erforderlich. Zudem sollten solche Technologien zugänglich sein, um ein breites Publikum zu erreichen. Diese Dissertation erforscht die digitale Fabrikation als Schlüsseltechnologie, um diese Probleme zu adressieren. Sie trägt vier neue Design- und Fabrikationsansätze für das Prototyping interaktiver Objekte mit reichhaltigen Materialien bei. Diese ermöglichen einfaches, zugängliches und vielseitiges Design und Fabrikation von interaktiven Objekten mit individueller Dehnbarkeit, Ein- und Ausgabe auf komplexen Geometrien und vielfältigen Materialien, taktiler Ausgabe auf 3D-Objektgeometrien und der Fähigkeit ihre Form und Materialeigenschaften zu ändern. Insgesamt trägt diese Dissertation zum Fortschritt der Bereiche der digitalen Fabrikation, des Rapid Prototyping und des Ubiquitous Computing in Richtung des größeren Ziels, der Exploration interaktiver Objekte mit reichhaltigen Materialien als eine neue Generation von physischen Interfaces, bei

Physical sketching tools and techniques for customized sensate surfaces

Sensate surfaces are a promising avenue for enhancing human interaction with digital systems due to their inherent intuitiveness and natural user interface. Recent technological advancements have enabled sensate surfaces to surpass the constraints of conventional touchscreens by integrating them into everyday objects, creating interactive interfaces that can detect various inputs such as touch, pressure, and gestures. This allows for more natural and intuitive control of digital systems. However, prototyping interactive surfaces that are customized to users' requirements using conventional techniques remains technically challenging due to limitations in accommodating complex geometric shapes and varying sizes. Furthermore, it is crucial to consider the context in which customized surfaces are utilized, as relocating them to fabrication labs may lead to the loss of their original design context. Additionally, prototyping high-resolution sensate surfaces presents challenges due to the complex signal processing requirements involved. This thesis investigates the design and fabrication of customized sensate surfaces that meet the diverse requirements of different users and contexts. The research aims to develop novel tools and techniques that overcome the technical limitations of current methods and enable the creation of sensate surfaces that enhance human interaction with digital systems.Sensorische Oberflächen sind aufgrund ihrer inhärenten Intuitivität und natürlichen Benutzeroberfläche ein vielversprechender Ansatz, um die menschliche Interaktionmit digitalen Systemen zu verbessern. Die jüngsten technologischen Fortschritte haben es ermöglicht, dass sensorische Oberflächen die Beschränkungen herkömmlicher Touchscreens überwinden, indem sie in Alltagsgegenstände integriert werden und interaktive Schnittstellen schaffen, die diverse Eingaben wie Berührung, Druck, oder Gesten erkennen können. Dies ermöglicht eine natürlichere und intuitivere Steuerung von digitalen Systemen. Das Prototyping interaktiver Oberflächen, die mit herkömmlichen Techniken an die Bedürfnisse der Nutzer angepasst werden, bleibt jedoch eine technische Herausforderung, da komplexe geometrische Formen und variierende Größen nur begrenzt berücksichtigt werden können. Darüber hinaus ist es von entscheidender Bedeutung, den Kontext, in dem diese individuell angepassten Oberflächen verwendet werden, zu berücksichtigen, da eine Verlagerung in Fabrikations-Laboratorien zum Verlust ihres ursprünglichen Designkontextes führen kann. Zudem stellt das Prototyping hochauflösender sensorischer Oberflächen aufgrund der komplexen Anforderungen an die Signalverarbeitung eine Herausforderung dar. Diese Arbeit erforscht dasDesign und die Fabrikation individuell angepasster sensorischer Oberflächen, die den diversen Anforderungen unterschiedlicher Nutzer und Kontexte gerecht werden. Die Forschung zielt darauf ab, neuartigeWerkzeuge und Techniken zu entwickeln, die die technischen Beschränkungen derzeitigerMethoden überwinden und die Erstellung von sensorischen Oberflächen ermöglichen, die die menschliche Interaktion mit digitalen Systemen verbessern

Design and application of a contact barcode reader, for use on low-visibility printed conductive patterns

This thesis was submitted for the degree of Master of Philosophy and awarded by Brunel University.This thesis presents the design and development of a hand-held electronic reader, designed to decode conductive patterns printed on a paper substrate. Data read from the patterns, by the reader, is used to trigger events in the digital domain. The reader and associated conductive patterns are devices for linking paper documents with the digital world. The patterns are formed by masking conductive-coated paper with a non-conductive, printed lacquer. The reader is a low cost and ergonomic device, capable of transmitting the embedded data from the conductive paper to the computer. The first reader designed and developed was tethered to a computer by data cable, using the USB communication protocol. The second design was developed further, with transmission of data achieved by replacing the cable with short-range Bluetooth wireless technology. Both devices were designed and developed using embedded systems and low cost electronic components. Additional work was undertaken to optimise the device's mechanical structure, ergonomics and integration of hardware. Alongside the development of the reader, test and development work was carried out to optimise the printed media, in materials and design. User trials demonstrated that the complete printed and reading system was functional, with varied rates of success among participants. Further work is required to improve the conductivity of the coated paper, and the accuracy of the decoding algorithm.This work resulted from a research project funded by EU FP6

Fabrication and Application of Flexible Sensors

A transfer printing method was developed to transfer carbon nanotubes (CNTs) from polyethylene terephthalate (PET) film to poly(dimethyl siloxane) (PDMS) polymer. Carbon nanotubes are composed of carbon atoms arranged in a honeycomb lattice structure, which are electrically conducting. When embedded in a nonconducting polymer, carbon nanotubes impart electrical conductivity to the nanocomposite, thus forming a nanocomposite that has potential applications in highly sensitive strain and pressure sensors. Several printing methods have been studied to deposit carbon nanotubes onto PDMS, including inkjet printing. Inkjet printing is a desirable deposition method since it is low-cost, simple, and allows the processing of aqueous-based inks. However, directly inkjet printing carbon nanotubes onto PDMS has been a challenge because the printed film becomes non-uniform due to the uneven drying of the droplets. Therefore, a method of transfer printing was developed to embed carbon nanotubes uniformly in PDMS. The transfer printing method consists of first inkjet printing patterns of carbon nanotubes onto a PET film, which quickly absorbs the aqueous ink and allows uniformity of the printed carbon nanotube patterns. The next step is spin-coating PDMS on the PET film to cover the carbon nanotube patterns, followed by curing the PDMS. The following step is thermally treating the PET film to promote the transfer of carbon nanotubes to PDMS, and finally peeling off PDMS from PET film to complete the transfer of carbon nanotube patterns. The transferred patterns had widths as small as 125 µm, while the obtained PDMS thickness was as low as 27.1 µm, which enabled the fabrication of highly sensitive force and pressure sensors. The transfer printing method was employed to fabricate a two-dimensional force sensor, which was composed of lines of carbon nanotubes in the x and y directions. The transduction mechanism lies in the generation of strain on the carbon nanotube pattern. When strain is produced, the resistance of the pattern changes due to the increase or decrease of the number of conduction paths in the carbon nanotube pattern. The practical application as a two-dimensional sensor was shown by monitoring the touch force exerted by multiple objects on the sensor. Due to the flexibility and stretchability of PDMS, fabricated air pressure sensors were capable of detecting small pressure differences. The sensors were composed of a circular diaphragm containing inkjet-printed carbon nanotube patterns. When air pressure increased on one side of the diaphragm, the deflection caused a strain on the CNT line, thus changing its resistance. Pressure sensors with a diaphragm diameter of five millimeters, diaphragm thickness of 27.1 µm showed sensitivity of 10.99 percent change in resistance per kilopascal (%/kPa) and limit of detection of 3.1 Pa. The pressure sensor has potential applications in monitoring minute air pressure differences such as those generated by the breathing pattern. The application of the highly sensitive and biocompatible pressure sensor was shown through the measurement of the pressure generated by a 3D-printed respiratory system

Fully inkjet-printed two-dimensional material field-effect heterojunctions for wearable and textile electronics.

Fully printed wearable electronics based on two-dimensional (2D) material heterojunction structures also known as heterostructures, such as field-effect transistors, require robust and reproducible printed multi-layer stacks consisting of active channel, dielectric and conductive contact layers. Solution processing of graphite and other layered materials provides low-cost inks enabling printed electronic devices, for example by inkjet printing. However, the limited quality of the 2D-material inks, the complexity of the layered arrangement, and the lack of a dielectric 2D-material ink able to operate at room temperature, under strain and after several washing cycles has impeded the fabrication of electronic devices on textile with fully printed 2D heterostructures. Here we demonstrate fully inkjet-printed 2D-material active heterostructures with graphene and hexagonal-boron nitride (h-BN) inks, and use them to fabricate all inkjet-printed flexible and washable field-effect transistors on textile, reaching a field-effect mobility of ~91 cm2 V-1 s-1, at low voltage (<5 V). This enables fully inkjet-printed electronic circuits, such as reprogrammable volatile memory cells, complementary inverters and OR logic gates

Printed Organic Photodiodes with Enhanced Performance and Simplified Processing

Zukünftige Technologien in den Bereichen Datenübertragung, Industrieautomatisierung, Verbraucherelektronik und medizinische Diagnostik werden von der Entwicklung optischer Sensortechnologien profitieren, die eine kosteneffiziente Fertigung, mechanische Flexibilität, personalisiertes Design und maßgeschneiderte Funktionalität bieten. Eine vielversprechende Klasse von Sensoren, die diese Eigenschaften gewähren, sind Photodetektoren auf der Basis organischer Halbleiter. Sogenannte organische Photodioden (OPDs) haben sich in den letzten Jahren rasch in ihrer Leistung verbessert und ihr Potenzial als komplementäre Technologie zu anorganischen Bauelementen unter Beweis gestellt. Vor allem aber ermöglicht Prozessierbarkeit aus der Flüssigphase die Bauteilfertigung mit industriellen Drucktechniken. Der große Parameterraum des Druckens in Verbindung mit den morphologischen und energetischen Anforderungen von OPDs führt jedoch zu einer Fülle von Herausforderungen, die den Übergang vom Labormaßstab zu relevanten Produktionsmethoden erschweren. In dieser Arbeit werden drei neue Konzepte für die OPD-Fertigung vorgestellt, die zur Bewältigung dieser Herausforderungen beitragen. Es werden alternative - und in einigen Fällen "unkonventionelle" - photoaktive Materialsysteme eingeführt, die gleichzeitig die Verarbeitung vereinfachen, die Leistung verbessern und zusätzliche Funktionalität bieten. Der erste Ansatz konzentriert sich auf die Verwendung von Isolatoren als Prozessadditive für die Herstellung von photoaktiven Schichten. Entgegen der Intuition behindert dies nicht die Funktionalität der OPDs, sondern verbessert sogar die Detektionsgeschwindigkeit durch eine Erhöhung der molekularen Ordnung der Halbleiterschicht. Ein zweiter Ansatz besteht in der Untersuchung einer neuartigen Materialklasse, nämlich den Nicht-Fulleren Akzeptoren (engl. non-fullerene acceptors, NFA), um die Empfindlichkeit in Richtung des nahen Infrarot-Bereichs zu erweitern und zu erhöhen. Diese Studie führte zur ersten Demonstration von digital gedruckten NFA-OPDs mit einer Rekordempfindlichkeit von über 750 nm und Detektionsgeschwindigkeiten im MHz-Bereich. Schließlich ermöglicht ein drittes Konzept die digitale Herstellung mehrfarbiger OPDs, indem ein innovatives Tintensystem entwickelt wird, das die viskoelastischen und optischen Eigenschaften erfolgreich entkoppelt, um die Fertigung zu vereinfachen und die spektrale Flexibilität von NFAs optimal ausnutzt. Die resultierende farbselektive Detektion ermöglicht die Integration der OPDs in ein Mehrkanal-Kommunikationssystem für sichtbares Licht (engl. visible light communication), das eine der vielversprechendsten aufkommenden Technologien im Bereich der optischen Datenübertragung darstellt. Alle drei Ansätze kombinieren herausragende Funktionalität und Leistung mit vereinfachten Herstellungsverfahren und tragen dazu bei das Potenzial von OPDs für das breite Feld der optischen Sensorik erfolgreich auszuschöpfen

Synthesis and Drop-on-Demand Deposition of Graphene Derivative Inks for Flexible Thin Film Electronics

This dissertation presents methods for deposition and post-processing of Graphene-Carboxymethyl Cellulose (G-CMC) and Graphene Oxide (GO) aqueous functional inks using a custom drop-on-demand (DOD) printer to fabricate mechanically flexible, non-transparent and transparent thin film electronic devices. Thin films on flexible substrates find use in lightweight, low profile, and conformable electronic devices. Such devices can include chemical sensors, flexible RFID tags, bioelectronics circuits, lightweight electronics for space systems, and transparent electrodes for optoelectronic systems. The goal of this research project is to provide simple methods for fabrication of these devices using environmentally friendly and easy to synthesize functional inks. Therefore, two graphene based inks are utilized; GO and a novel Carboxymethyl Cellulose (CMC) functionalized aqueous dispersion of Graphene, G-CMC. Proposed functional inks are deposited on treated substrates by DOD printing. Deposited thin films were post-processed by use of a muffle furnace or a pulsed laser system. Furthermore, gold doped G-CMC films and G-Silver Nanoprism (G-AgNP) composite inks were developed to enhance film electrical properties. Inkjet printed films on glass substrates were characterized in terms of their electrical, optical, and mechanical properties. Correlations between film thickness, optical transmittance, and conductivity were investigated. It was possible to deposit homogeneous thin films at 100 nm to 2000 nm thickness. G-CMC films exhibited good scaling of conductance where thicker films had ~ 660 Ω/sq sheet resistance. Gold doped and G-AgNP composite semi-transparent films exhibited enhanced conductance with sheet resistances of ~ 700 Ω/sq at 35% transparency and ~ 374 Ω/sq at 50% transparency, respectively. Laser assisted treatment of samples was conducted to investigate two opportunities; pulsed laser thermal treatment and pulsed laser micromachining on rigid and flexible substrates. Effect of laser parameters was investigated to establish guidelines for thin film thermal treatment and micromachining Finally, novel flexible sensors and circuits were fabricated to demonstrate task driven performance of proposed materials and methods. Based on the presented work, proposed methods and functional inks show promise for fabricating simple electronic devices on flexible and rigid substrates. It is believed that presented advances may benefit industrial fields that require scalable and simple thin film fabrication methods