Flexible and Stretchable Electronics

Flexible and stretchable electronics are receiving tremendous attention as future electronics due to their flexibility and light weight, especially as applications in wearable electronics. Flexible electronics are usually fabricated on heat sensitive flexible substrates such as plastic, fabric or even paper, while stretchable electronics are usually fabricated from an elastomeric substrate to survive large deformation in their practical application. Therefore, successful fabrication of flexible electronics needs low temperature processable novel materials and a particular processing development because traditional materials and processes are not compatible with flexible/stretchable electronics. Huge technical challenges and opportunities surround these dramatic changes from the perspective of new material design and processing, new fabrication techniques, large deformation mechanics, new application development and so on. Here, we invited talented researchers to join us in this new vital field that holds the potential to reshape our future life, by contributing their words of wisdom from their particular perspective

Laser Micromachining: An Enabling Technology for Functional Surfaces and Materials

L'abstract è presente nell'allegato / the abstract is in the attachmen

전자피부 어플리케이션을 위한 투명 키리가미 전극 개발

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 기계공학부, 2019. 2. 고승환.For relieving the inconvenience while wearing electronic devices, stretchability and imperceptibility are essentially required characteristics for desired form of electronic-skin devices. Yet accomplishing these properties simultaneously is still challenging although some progress has been made on materials and structure designs. Here, we suggest a novel fabrication technique brining an idea from kirigami, Japanese ancient paper-cutting craft, to enable transparent and highly conductive electrodes to be deformable. By using facile and fast laser patterning process, we show transparent kirigami electrodes composed of silver nanowires partially embedded in ultra-thin colorless-polyimide film. Owing to rapid laser patterning method, versatile patterns are developed in few minutes under non-vacuum and room temperature condition. These patterns impart tunable elasticity to the electrodes, which can be stretched over 400% tensile strain with strain-invariant electrical property and also show good electromechanical stability even after 10,000 cycles of 400% stretching while exhibiting high optical transparency (more than 80%). In addition, gold coating on the exposed surface of silver nanowires ensure biocompatibility and improved electrical stability, preventing allergic reaction of skin and oxidation of the silver nanowires. The transparent kirigami electrodes with customizable elasticity pave the innovative way that offers facile construction of appropriate geometries for achieving multi-functional transparent and wearable electronic skin applications. The versatility of this work is demonstrated by ultra-stretchable transparent kirigami heater for personal thermal management and conformal transparent kirigami electrophysiology sensor for continuous health monitoring of human body conditions. Finally, by integrating electronic-skin sensors with a quadrotor, we have successfully demonstrated human-machine interface using our stretchable transparent kirigami electrodes.웨어러블 전자소자를 착용할 때 이질감을 최소화하기 위해 전자피부의 형태로서 사용되는 전극은 투명하여 눈에 잘 보이지 않아야 하고, 피부처럼 구부러지며 늘어날 수 있어야 한다. 하지만 전극의 재료와 구조적 측면에서 많은 연구가 진행되었음에도 여전히 투명하면서 늘어나는 전극을 구현하는 데 어려움이 많다. 본 논문에서는 이러한 어려움을 극복하기 위해 무색의 폴리이미드와 은 나노와이어를 기반으로 한 플렉서블 투명전극에 레이저 공정을 이용한 키리가미 패턴을 넣음으로써 스트레처블 투명전극을 구현하는 공정을 고안했다. 이를 바탕으로 본래 길이의 400%까지 늘이는 반복인장시험을 10,000회 이상 진행한 후에도 저항변화가 거의 없는 투명전극을 제작했다. 또한 드러난 은 나노와이어의 표면에 선택적으로 금을 코팅함으로써 전극의 산화를 방지하고 생체에 부착 및 착용하기에 적합할 수 있도록 했다. 본 연구에서는 이를 이용해 용도에 맞게 디자인된 키리가미 패턴을 가진 투명전극을 적용한 웨어러블 히터와 생체신호 측정센서를 제작했다. 더 나아가 근전도 센서를 양팔에 부착한 후 역동적인 움직임에 대응되는 근전도 신호를 읽어 쿼드로터를 조종하는 시스템을 구축함으로써 진보된 인간-기계 인터페이스를 구현했다.Chapter 1. Introduction 1 1.1. Study Background 1 1.2. Purpose of Research 3 Chapter 2. Experiment 5 2.1. Fabrication of Transparent Kirigami Electrodes 5 2.2. Synthesis of Silver Nanowires 7 2.3. Fabrication of AgNWs/cPI Electrodes 8 2.4. Laser Ablation Patterning Process 9 2.5. Gold Coating on The Exposed AgNWs 10 2.6. Finite Element Simulation 12 Chapter 3. Result 13 3.1. Characterization of Transparent Kirigami Electrodes 13 3.2. Highly Stretchable and Transparent Kirigami Heater 18 3.3. Conformal and Transparent Kirigami Electrophysiology Sensor 20 3.4. Human-Machine Interface for Controlling a Quadrotor 23 Chapter 4. Conclusion 26 References 27 Abstract in Korean 30Maste

Laser-scribed graphene for sensors: preparation, modification, applications, and future prospects

Sensors are widely used to acquire biological and environmental information for medical diagnosis, and health and environmental monitoring. Graphene is a promising new sensor material that has been widely used in sensor fabrication in recent years. Compared with many other existing graphene preparation methods, laser-scribed graphene (LSG) is simple, low-cost, environmentally friendly, and has good conductivity and high thermal stability, making it widely used in the sensor field. This paper summarizes existing LSG methods for sensor fabrication. Primary LSG preparation methods and their variants are introduced first, followed by a summary of LSG modification methods designed explicitly for sensor fabrication. Subsequently, the applications of LSG in stress, bio, gas, temperature, and humidity sensors are summarized with a particular focus on multifunctional integrated sensors. Finally, the current challenges and prospects of LSG-based sensors are discussed

Laser synthesized gold nanoparticles for high sensitive strain gauges

Ankara : Materials Science and Nanotechnology Program and the Graduate School of Engineering and Science of Bilkent University, 2013.Thesis (Master's) -- Bilkent University, 2013.Includes bibliographical references leaves 65-70.Recently, the conduction properties of nanoparticle films have received great deal of attention due to their unique properties attributed to quantum tunneling effect. Quantum tunneling effect, highly dependent on quantum barrier height and width, is very attractive for sensor applications. Resistive strain gauges based on gold nanoparticle (Au-NP) films show high strain sensitivity. These strain gauges are applicable for miniature applications because of its size. In addition, this nanoparticle films could be also used for various applications such as pressure and vapor sensors. Clean surfaces of laser generated Au-NPs provide high tunneling decay constant. Therefore, these films are promising for high sensitive sensor applications. In our study, the Au-NPs were directly synthesized in deionized water by nanosecond laser ablation method. The clean surface, size and aggregate clusters of Au-NPs offer advantages for high sensitivity strain sensor. We prepared Au-NPs films on flexible PDMS substrate by using hands-on drop-cast method. To obtain high gauge factor, we also investigated the nanoparticle concentration on the thin films. Laser-generated AuNPs films demonstrated gauge factor of ∼300 for higher than 0.22% strain and ∼80 for the strain lower than 0.22%, which is favorably comparable to reported sensitivities for strain sensors based on Au-NPs. Mechanical characterizations for the prolonged working durations suggest long term stability of these strain sensors. We discuss several models describing conductance of Au-NP films in low and high strain regimes. To the best of our knowledge, the conduction of laser generated Au-NP films has not been studied up to date, and it is the first study that shows high strain sensitivity of these films. Au-NP films may be promising for sensor applications.Burzhuev, SalamatM.S

From biomass to wearable devices: laser-induced graphene derived from lignin for ultrasensitive sensing

Laser-indued graphene (LIG) is 3D porous structure with many promising properties. Lignin-based precursor has shown its unique properties in generating high quality LIG among various organic carbon-based substrates. In this study, we explored LIG derived from lignin for an ultrasensitive strain sensor for the first time. The main procedures included the precursor preparation, laser writing process, sensor fabrication, sensitivity test to strains and vibrations, and performance test on human body. The results demonstrated an excellent performance of our strain sensors with high accuracy and ultrasenstivity, suggesting the promising future of lignin valorization into LIG and futher wearable devices.Includes bibliographical references

LASER SHOCK IMPRINTING OF METALLIC NANOSTRUCTURES AND SHOCK PROCESSING OF LOW-DIMENSIONAL MATERIALS

Laser shock imprinting (LSI) is proposed and developed as a novel ultrafast room-temperature top-down technique for fabricating and tuning of plasmonic nanostructures, and processing of one-dimensional semiconductor nanowires and two-dimensional crystals. The technique utilizes a shock pressure generated by laser ablation of sacrificial materials. Compared with conventional technologies, LSI features ambient condition, good scalability, low cost and high efficiency

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