Smart Wallpapers Research Articles

Debossed Contact Printing as a Patterning Method for Paper-Based Electronics.

The proliferation of printed electronic devices is feeding the growth of the Internet of Things, with devices deployed everywhere to collect and communicate data. At the same time, the increase in low-cost disposable devices is a cause for serious environmental concern. In particular, widely used plastic substrates such as poly(ethylene terephthalate) are persistent hazards to the environment. Paper is promising as a greener substrate for printed electronics because it is biodegradable and sourced from renewable materials as well as being low cost and compatible with roll-to-roll printing. However, the porous microstructure of paper promotes wicking of functional inks, leading to poor electrical performance and printing resolution. Hydrophobic coatings applied to the surface of paper create a planarized, printable surface, but these materials may compromise biodegradability and/or recyclability. This paper describes a new resist-free patterning method for printed paper-based electronics that takes advantage of the porous structure of paper. Debossed contact printing uses the pressure from a debossing tip to compress the porous structure of paper and create a patterned relief structure. Printing functional inks with an unpatterned roller deposits ink only on the raised regions of the relief structure. We demonstrate debossed contact printing of silver, carbon black, and conducting polymer inks and show that this new fabrication method is suitable for the fabrication of printed devices with dense features. We demonstrate the fabrication of antennas and patterned electrodes for RFID and smart wallpaper applications, respectively.

Electrical and mechanical properties of self-supported hydroxypropyl methylcellulose-polyaniline conducting films.

The purpose of this work was to develop a simple method to produce self-supported films composed of hydroxypropyl methylcellulose (HPMC) and polyaniline (PANI) by the direct mixture of aqueous dispersions of both polymers with subsequent drying. The addition of HPMC, a cellulose derivative with an excellent film-forming capacity, was fundamental to overcoming the poor processability of PANI, which impairs its use in many technological applications. All films showed conductivity in the order of 10-2 to 10-3 S cm-1, which is in the range for metals or semiconductors. The typical electroactivity of PANI was also maintained in the hybrid films. The thermal stability and the mechanical properties of the pristine PANI were also improved with the addition of HPMC. Cellulose-containing conducting polymers can be considered a material of the future, with possible applications in several areas, such as smart wallpapers, e-papers, and sensors.

Highly-sensitive fire alarm system based on cellulose paper with low-temperature response and wireless signal conversion

Highly sensitive smart sensors for early fire detection with remote warning capabilities are urgently required to improve the fire safety of combustible materials in diverse applications. The highly-sensitive fire alarm can detect fire situation within a short time quickly when a fire disaster is about to occur, which is conducive to achieve fire tuned. Herein, a novel fire alarm is designed by using flame-retardant cellulose paper loaded with graphene oxide (GO) and two-dimensional titanium carbide (Ti3C2, MXene). Owing to the excellent temperature dependent electrical resistance switching effect of GO, it acts as an electrical insulator at room temperature and becomes electrically conductive at high temperature. During a fire incident, the partial oxygen-containing groups on GO will undergo complete removal, which results in the conductivity transformation.Besides the use of GO feature, this work also introduces conductive MXene to enhance fire detection speed and warning at low temperature, especially below 300 {\deg}C. The designed flame-retardant fire alarm is sensitive enough to detect fire incident, showing a response time of 2 s at 250 {\deg}C, which is calculated by a novel and quantifiable technique. More importantly, the designed fire alarm sensor is coupled to a wireless communication interface to conveniently transmit fire signal remotely. Therefore, when an abnormal temperature is detected, the signal is wirelessly transmitted to a liquid crystal display (LCD) screen when displays a message such as "FIRE DANGER". The designed smart fire alarm paper is promising for use as a smart wallpaper for interior house decoration and other applications requiring early fire detection and warning.

Bio-inspired flexible vibration visualization sensor based on piezo-electrochromic effect

Monitoring structural vibration can provide quantitative information for both structural health evaluations and early-warning maintenance. The most classic vibration-based structural health monitoring is equipped with piezoelectric accelerometers, which is expensive and inconvenient due to cumbersome and time-consuming sensor installation and high power-consumptive data acquisition systems. One other main challenge with these systems is the inherent limitations for multi-point monitoring in critical elements with curvature due to their non-conformability. Here, inspired by the chameleon, we report a cost-effective, flexible and conformal, self-powered vibration sensor based on elasto-electro-chemical synergistic effect of piezoelectricity and electrochromism. The sensor can provide not only in-situ visualization, but also ex-situ recording of structural vibration due to the non-volatile color memory effect of electrochromism. The passive sensor system is composed of two distinct electronic components — ternary Pb(In1/2Nb1/2)O3Pb(Mg1/3Nb2/3)O3PbTiO3 piezoelectric single crystal ribbon sensors and a solid-state tungsten trioxide electrochromic indicator driven by vibration-induced voltage generated by the piezoelectric ribbons. The proposed piezo-electrochromic based passive non-volatile visualization sensor may find diverse applications in structural health monitoring, smart wallpapers, and medical injury rehabilitation.

Liquid-State Environment Sensors Using Liquid Metal

Flexible devices have many potential applications in wearable electronics, robotics, health monitoring, and more. Mechanically deformable devices and sensors such as flexible devices enable conformal coverage of electronic systems on curved and soft surfaces. Sensors utilizing liquids confined in soft templates as the sensing component present the ideal platform for such applications, as liquids are inherently more deformable than solids. However, to date, current liquid-metal based strain sensors are incapable of resolving small pressure changes in the few kPa range, making them unsuitable for applications such as heart-rate monitoring which require much lower pressure detection resolution. In addition, liquid-based devices have been limited to metal lines based on a single liquid component given the difficulty in the fabrication of liquid-based junctions due to intermixing. Here we demonstrate state-of-art microfluidic environmental sensors using liquid metal, highly sensitive pressure sensor based on tactile diaphragm pressure sensor, and temperature/humidity/oxygen sensors with mechanically robust liquid-liquid “heterojunction”. This report will present an important advancement towards the realization of liquid-state electronic systems. Introduction Electronic devices and sensors which exhibit large amounts of mechanical deformability have many applications such as in smart wallpapers and human-machine interfaces for prosthetics. In this regard, tremendous advancements have been made in engineering solid-state electronic materials and devices on elastic substrates. Recently, sensors based on using liquid active components embedded within soft elastomeric substrates have shown much promise for such applications as liquids present the ultimate limit in deformability. In this paper, we report four microfluidic sensors using liquid metals, highly sensitive pressure sensor based on tactile diaphragm pressure sensor, and temperature/humidity/oxygen sensors with liquid-liquid “heterojunction”. The work presents an important step towards the potential realization of liquid-state electronic systems that offer new form factors and functionality. Current Result < Microfluidic diaphragm pressure sensor> In both sensors, the devices were fabricated by photolithography techniques using poly(dimethylsiloxane) (PDMS) as the substrate, and eutectic GaInSn (Galinstan) as electrodes. A microfluidic tactile diaphragm pressure sensor based on embedded Galinstan microchannels (70 µm width 70 µm height) capable of resolving sub-50 Pa changes in pressure with sub-100 Pa detection limits and a response time of 90 ms is demonstrated(Fig. 1). An embedded equivalent Wheatstone bridge circuit makes the most of tangential and radial strain fields, leading to high sensitivities of 0.0835 kPa-1 change in output voltage. The Wheatstone bridge also provides temperature self-compensation, allowing for operation in the range of 20-50 °C. As examples of potential applications, a polydimethylsiloxane (PDMS) wristband with an embedded microfluidic diaphragm pressure sensor capable of real time pulse monitoring(Fig. 2) and a PDMS glove with multiple embedded sensors to provide comprehensive tactile feedback of a human hand when touching or holding objects are demonstrated(Fig. 3). <Temperature/humidity/oxygen sensors with liquid-liquid “heterojunction”> In termes of temperature/humidity/oxygen sensors with liquid-liquid “heterojunction”, liquid metal was used as electrode, and ionic liquids as a sensing material(Fig. 4 and 5). As shown in Fig. 6, equivalent circuit of the sensors were established based on Nyquist plot The sensor showed stable sensitivity to temperature without hysteresis as shown in Fig. 7 with a 0.039/°C increase in conductivity, which is quite high compared to other reports. We also show proof of concept for humidity and oxygen gas sensing using three kinds of ionic liquids, 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][Otf]), 1-Butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMPYR][NTf2]). As shown in Fig. 7, the sensitivity of each ionic liquid to humidity and oxygen differed depending on the ionic liquid. For each type of stimuli, the sensing can be optimized by choosing the proper ionic liquid. In the future, multiple liquid heterojunction sensors, each with a different ionic liquid may be multiplexed into a fully integrated system to sense different stimuli with calibrated response. Figure 1

Carbon Nanotube Flexible and Stretchable Electronics.

The low-cost and large-area manufacturing of flexible and stretchable electronics using printing processes could radically change people’s perspectives on electronics and substantially expand the spectrum of potential applications. Examples range from personalized wearable electronics to large-area smart wallpapers and from interactive bio-inspired robots to implantable health/medical apparatus. Owing to its one-dimensional structure and superior electrical property, carbon nanotube is one of the most promising material platforms for flexible and stretchable electronics. Here in this paper, we review the recent progress in this field. Applications of single-wall carbon nanotube networks as channel semiconductor in flexible thin-film transistors and integrated circuits, as stretchable conductors in various sensors, and as channel material in stretchable transistors will be discussed. Lastly, state-of-the-art advancement on printing process, which is ideal for large-scale fabrication of flexible and stretchable electronics, will also be reviewed in detail.

Electret Film-Enhanced Triboelectric Nanogenerator Matrix for Self-Powered Instantaneous Tactile Imaging

We report the first self-powered electronic skin that consists of light-emitting diode (LED) and triboelectric nanogenerator (TENG) arrays that can be utilized for spatially mapping applied instantaneous-touch events and tracking the movement location of the target object by recording the electroluminescent signals of the LEDs without external power sources. The electret film-based TENG can deliver an open-circuit voltage of about -1070 V, a short-circuit current density of 10 mA/m(2), and a power density of 288 mW/m(2) on an external load of 100 MΩ. The LEDs can be turned on locally when the back surface of the active matrix is touched, and the intensity of the emitted light depends on the magnitude of the applied local pressure on the device. A constructed active matrix of the LED-TENG array (8 × 7 pixels) can achieve self-powered, visual, and high-resolution tactile sensing by recording the electroluminescent signals from all of the pixels, where the active size of each pixel can be decreased to 10 mm(2). This work is a significant step forward in self-powered tactile-mapping visualization technology, with a wide range of potential applications in touchpad technology, personal signatures, smart wallpapers, robotics, and safety-monitoring devices.

User-interactive electronic skin for instantaneous pressure visualization

Electronic skin (e-skin) presents a network of mechanically flexible sensors that can conformally wrap irregular surfaces and spatially map and quantify various stimuli. Previous works on e-skin have focused on the optimization of pressure sensors interfaced with an electronic readout, whereas user interfaces based on a human-readable output were not explored. Here, we report the first user-interactive e-skin that not only spatially maps the applied pressure but also provides an instantaneous visual response through a built-in active-matrix organic light-emitting diode display with red, green and blue pixels. In this system, organic light-emitting diodes (OLEDs) are turned on locally where the surface is touched, and the intensity of the emitted light quantifies the magnitude of the applied pressure. This work represents a system-on-plastic demonstration where three distinct electronic components--thin-film transistor, pressure sensor and OLED arrays--are monolithically integrated over large areas on a single plastic substrate. The reported e-skin may find a wide range of applications in interactive input/control devices, smart wallpapers, robotics and medical/health monitoring devices.

Semantic ambient media—an introduction

The medium is the message! And the message was literacy, media democracy and music charts. Mostly one single distinguishable medium such as TV, the Web, the radio, or books transmitted the message. Now in the age of ubiquitous and pervasive computing, where information flows through a plethora of distributed interlinked media--what is the message ambient media will tell us? What does semantic mean in this context? Which experiences will it open to us? What is content in the age of ambient media? Ambient media are embedded throughout the natural environment of the consumer--in his home, in his car, in restaurants, and on his mobile device. Predominant sample services are smart wallpapers in homes, location based services, RFID based entertainment services for children, or intelligent homes. The goal of this article is to define semantic ambient media and discuss the contributions to the Semantic Ambient Media Experience (SAME) workshop, which was held in conjunction with the ACM Multimedia conference in Vancouver in 2008. The results of the workshop can be found on: www.ambientmediaassociation.org .

Electro-active paper for a durable biomimetic actuator

Cellulose electro-active paper (EAPap), known as a smart material, has merits in terms oflow voltage operation, light weight, dryness, low power consumption, biodegradability,abundance and low price. Since EAPap requires low power consumption, a remotely drivenactuator has been proposed using microwave power transmission. This concept is attractivefor many biomimetic systems such as crawling micro-insect robots, flying objects likedragon flies and smart wallpapers. However, the actuation performance of EAPap issensitive to humidity and degrades with time. Thus, in this paper, a durable EAPap isstudied. The fabrication of EAPap is explained and the actuation performance is shownwith applied electric field, frequency, humidity level and time. The fabrication processincludes dissolving cellulose fibers, eliminating solvent and Li ions with a mixture ofdeionized water and isopropyl alcohol, washing with water, drying and coating withgold. The morphology of the fabricated EAPap is analyzed by taking scanningelectron microscope images and x-ray diffractograms. The actuation performance istested in terms of bending displacement with frequency, time and humidity level

Cellulose Electroactive Paper (EAPap): The Potential for a Novel Electronic Material

AbstractCellulose electro-active paper (EAPap) has attracted much attention as a new smart electronic material to be utilized as mechanical sensors, bio compatible applications and wireless communications. The thin EAPap film has many advantages such as lightweight, flexible, dryness, biodegradable, easy to chemically modify, cheap and abundance. Also EAPap film has a good reversibility for mechanical performance, such as bending movement, under electric field. The main actuation mechanism governed by piezoelectric property can be modulated by material direction and stretching ratio during process. In this paper we present the overview as well as fabrication process of cellulose EAPap as a novel smart material. Also we propose the method to enhance the piezoelectricity, its mechanical and electromechanical properties. In addition, the fabrication of high quality metal patterns with Schottky diode on the cellulose surface is an initiating stage for the integration of the EAPap actuator and electronic components. The integration of flexible actuator and electronic elements has huge potential application including flying magic carpets, microwave driven flying insets and micro-robots and smart wall papers.

In-plane strain of electro-active paper under electric fields

Electro-active papers (EAPap) made with cellulose have been known as a biomimetic actuator material according to their merits in terms of large bending deformation, low actuation voltage, ultra-lightweight, and biodegradability. This out-of-plane bending deformation is useful for achieving flapping wings, micro-insect robots, and smart wallpapers. On the other hand, in-plane strains, such as extension and contraction of EAPap materials are also promising for artificial muscle applications since the Young's modulus of EAPap materials is large. This paper first reports the experimental investigation of the in-plane strain of EAPap materials in the presence of electric fields. The EAPap samples preparation and the in-plane strain measurement system are explained. The test results are shown in terms of electric field, frequency and the orientation of the samples. The power consumption and the strain energy of EAPap samples are discussed. Although there are still unknown facts in EAPap materials, this in-plane strain may be useful for artificial muscle applications.

Electro-Active Papers for Remotely-Driven Smart Actuators

This paper introduces the concept of remotely-driven smart actuator utilized by electro-active paper (EAPap). The feature of remotely-driven smart actuator offers unique performance and application capabilities and exploit many of these unique capabilities. Since the microwave-driven actuator does not require carry-on-battery, ultra-lightweight, and distributed micro size actuators can be made. A dipole rectifying antenna (rectenna) array receives the microwave and converts it into a DC power. Recently, cellulose based paper has been came across as an lectroactive paper (EAPap) material so as to be used as artificial muscles for biomimetic insects. Since the power requirement of EAPap is less than the safety limit of microwave power in air, the EAPap actuators can be driven by wireless microwave power. This idea is useful for specific applications that require multifunctional capabilities such as smart skin, ultra-lightweight space structures, micro robots, flapping wing for insect-like flying objects and smart wall paper as well. Current research status along with its issues is addressed including a hybrid actuator of EAPap and conducting polymers that will enhance the performance of the actuator.

Sensate Media — Multimodal Electronic Skins as Dense Sensor Networks

In this paper, we introduce the concept of building electronic sensate skins as extremely dense, multimodal, systolic sensor networks. In this fashion, the copious signals produced by the skin's receptors are reduced by the network itself, and only high-level features are routed out peer-to-peer, avoiding complex wiring requirements while promising to enable scalability across large areas. Our architectures and algorithms have been inspired by biological skin, where signals from receptors are enhanced or suppressed by processing in the receptor cells and nervous system before arriving at the brain. We illustrate this concept with work in progress on two test beds, the Pushpin Computer, an easily configurable, planar array of over 100 nodes set up as 'smart wallpaper', and the Tribble, a sphere coated with over 500 diverse tactile and noncontact sensor channels processed in 32 interconnected sensor 'cells'. We also introduce the Z-Tiles, a collaborative project that has resulted in a pressure-imaging floor realised through a collection of pixilated floor tiles configured as a mesh sensor network. We conclude with a technology roadmap for scaling to higher densities.