Smart Garment Design 3. Materials Sungmin Kim SEOUL NATIONAL UNIVERSITY Conductive Material Conductive Textile Material In the early stage... Manufactured primarily for medical and industrial purposes Antimicrobial, antistatic, EMF (electromagnetic field) shielding purpose Not sold in smaller quantities Aesthetic aspects have not been well considered Nowadays... Available for consumer products Gloves for touch screen devices Sensors for heart rate or brain wave Conductive flexible electrodes Wide range of aesthetic options are available 2
Metal Fiber Conductive Fiber Characteristics Powerful raw material that can be used in a variety of projects Soft and light weight It can be spun, felted, and more Example Beknix, e-thread Stainless multifilament fiber Stainless steel fiber 3 Metallized Fiber Conductive Fiber Characteristics Fiber coated with metal Example Organza Silk filament wrapped with thin gold foil AmberStrandQ (Sycom) PBO (Polybenzoxazole) fiber wrapped with metal ContaX (Nobel Biometerial) Fiber containing silver Embroidered Antenna 4
Fiber from Inherently Conductive Polymer Conductive Polymer Studied since 1977 Won Nobel prize for Heeger, MacDiarmid, Shirakawa (2000) Conductive Fiber Example Polyaniline (PANI) Polypyrrole 5 Conductive Carbon Nano Tube Fiber Characteristic High tenacity High conductivity Conductive Fiber 6
Cotton-Wrapped Nichrome Yarn Structure Conductive Yarn Combed cotton yarn wrap the nichrome wire Wrapping is carried out by braiding technique Characteristics Coarser count yarn would be better Provides better wrapping with high surface area Better heat dissipation for preventing thermal shock Use Heating fabric Braided Yarn 7 Copper Core Yarn Structure Conductive Yarn Core-sheath type yarn Copper core filament is wrapped by cotton fiber by friction spinning Use Electrically Conductive fabric 8
Copper Core Yarn Industrial Importance Conductive Yarn Used to develop sensor wears and signal-transferring applications Defense, medical, and technical textiles Can be woven and knit into special fabrics Antielectrostatic fabric Electrostatic dissipating fabric Telecommunication textile device Electromagnetic shielding fabric Body temperature control jacket 9 Optical Core Conductive POF Yarn Structure Conductive Yarn POF (plastic optical fiber) is wrapped by cotton sliver using friction spinning system Use Communication fabric Illuminated fabric 10
Working with Conductive Yarn Conductive Yarn Hand Sewing Needle with a larger eye is needed Secure knot is needed Conductive yarn can be a bit slippery Fabric glue is sometimes required Machine Sewing Use the conductive yarn in the bobbin Prevention of Shorts Most conductive yarns are uninsulated Keep the circuits neat, trim, and organized 11 Properties of Conductive Yarn Thickness Conductive Yarn Determines the type of needle and the availability for sewing machine The more plys, the less resistive the yarn will be Resistance One of the most important factors to consider when choosing a conductive yarn Affects how they can be used in a circuit Material Different materials have different conductivity and physical properties Insulation Insulated conductive yarn does exists However, there are no insulated conductive yarn available in small quantities 12
Characteristics of Conductive Fabric Lower Resistance than Conductive Yarn Do a better job in circuits with higher-current demands Conductive Fabric Working with Conductive Fabric Sewing Conductive fabric can be sewn just like any other fabric Quilting and applique techniques can be used Prevention of Shorts Yarns from frayed piece can wander and inadvertently create shorts Can be mitigated through hemming, serging, or other traditional sewing techniques Iron-on Adhesive Conductive fabric can be purchased with iron-on adhesive already applied 13 Properties of Conductive Fabric Conductive Fabric Substrate Non-conductive base layer affect the care and comfort of the final product Nylon, polyester,... Weight and Thickness Important to consider in the context of the product Lightweight fabric for light t-shirt Stretch A stretch fabric can be helpful for a garment that needs to shape-shift or bend frequently Surface Resistance Many conductive fabrics have an extremely low surface resistance Color Most fabrics are in silver or copper 14
Other Conductive Material Conductive Felt How to Make Combining conductive fiber or conductive wool with sheep's wool Use Tactically pleasing variable resistor or electronic switch 15 Conductive Ribbon Type Single conductor type Multiple conductor type Uninsulated Insulated Other Conductive Material 16
Conductive Velcro Other Conductive Material Use Act as a secure and sensible electronic switch for clothing Conductive Paint Use Paint, draw, or silk screen circuits Works best on a nonporous substrate 17 Textile Sensors Definition A sensor in which fiber itself acts as a sensor Types Fiber Type Textile based Sensors Optical Fiber» Trouble-free transfer of information even at a high electric field» Can be used to temperature measurement by monitoring the refractive index of cladding» Can be used to pressure measurement using micro bending effect Yarn Type Used to detect the stress caused due to the influence of mechanical abrasion or UV 2D or 3D Fabric Type Bind multiple sensors to create a single sensor module Fabricated by weaving or knitting process. 18
Development Stages Material Selection Textile based Sensors Select suitable material for the delivery of signal energy Measurement Parameter Decision Determine the physical values to be measured as signal and develop measurement method Prototype Making Make a prototype using sewing, knitting, weaving, coating, embroidery, etc. Connectivity Test Solves the problem for the connection of the sensor and other electronic components Data analysis and evaluation Check the characteristics of the sensor by measuring the linearity of data, for example. Range Determination Determine the effective working range through repeated experiments 19 Examples Capacitive Sensor Textile based Sensors Principle Two opposing electrodes are separated by an insulating material When voltage is applied to the circuit, the electrode is charged to positive and negative The insulator prevent the electron current and an electric field is generated between electrodes The energy storage capacity is dependent on the distance between the electrodes Therefore, flexible textile electrodes can convert the change in pressure into electrical signals 20
Examples Textile based Sensors Temperature Sensor Can be made in various structures unlike electronic sensors Can cover a large area and measure the distribution of temperature over a large area Can measure the temperature of skin close to the body Can be used for physiological and medical monitoring Prepared by coating, weaving, knitting, embroidery, printing, etc. Operates on the principle of the thermocouple, resistance, and conductivity Special fiber optic type sensor Implementation FBG (Fiber Brag Grating) and the functional coating A single fiber can measure the temperature distribution over a large area 21 Examples Textile based Sensors Moisture Sensor The amount of water vapor in the air is very important in many manufacturing processes Monitoring and control of moisture is critical in the medical, industrial and domestic applications Sometimes the measurement over a wide area is necessary A fabric type sensor may be most appropriate Pressure Mapping Sensor A sensor for quantifying the pressure between two surfaces Based on a capacitive sensing element or piezoresistive element Applied to mat or socks to read the pressure acting on thigh, hips, feet, etc. Fabric made of pressure-sensitive filament may sense the pressure in all parts of the body 22
Examples Pressure Mapping Sensor Textile based Sensors Smart socks (Alpha-Fit) 23 Examples Pressure Mapping Sensor Textile based Sensors Project Jacquard (Google) 24
Color Changing Interactive Fabric Textile based Display Judit Eszter Karpati (Hungary, 2014) Interactive fabric using computer programming, engineering and electronic devices Slow moving textile displays to show the content, which react to environmental changes It changes color and pattern when heated up or pressed 25 Textile Battery Volvo (Sweden, 2013) Textile based Battery Turn body panels into batteries Same output with 50% reduction in battery weight 26
Textile based Battery Textile Battery KAIST (2013) Polyester fiber based battery Flexible, foldable, rechargeable (solar powered) Can have various form factors 27 Flexible Solar Cell Solar Cell Importance Infinite source of energy prior to the nuclear fusion technology Most renewable energy device cannot repay the energy to make during their lifetime Hydro, wind, etc. Photovoltaic (Solar) cell generates more energy than they consumed Alsema (2009), Lind (2015) Current Problems Solar cells are put between glass/polycarbonate plates due to weak nature Glass is fragile and polycarbonate glass is heavy Durable and lightweight material is needed Application of thin flexible plastic or metal films has been studied Lighter than polycarbonate glass but still fragile Textile-based solar cell has many advantages Light, durable, flexible,... 28
Textile based Solar Cell Using Organic Photovoltaic Fiber (Bedeloglu, 2010) Mass production of polymer film attached fabric is possible Flexible Solar Cell Solar cell film can be attached to fabric but it can be damaged by the bending of fabric Direct deposition of solar cell on the fabric is most desirable Cover Film Transparent conducting oxide Silicon film Metal film Organic conductor Fabric 29 Future of Textile based Solar Cell Most Suitable Power Sources Flexible Solar Cell Fashion products Conceptual products of solar powered jackets and backpacks have been made Most of them using the costly method of the integration of conventional silicone based solar cells Low-energy electronic devices Personal health status monitoring devices Sensors for wearable devices 30
Flexible Solar Cell Future of Textile based Solar Cell Wide Coverage Wide area textile based solar cell can be used for shade or canopy Solar tent that can supply power to various electronic equipment (PowerFilm Solar, Inc., USA) Personal solar panel for a soldier with radio communication, GPS, laser rangefinder, etc. 31 Piezoelectric Material Energy Harvesting Material Piezoelectricity One of the most important discoveries in 19th century Pressure applied to a material is converted in to electric energy Natural piezoelectric material Quartz, bone, tendons, enamel, dentin, etc. Synthetic piezoelectric material Some ceramic and polymer materials show piezo electricity Piezopolymers have some advantages over Piezoceramics such as piezoelectric performance or flexibility Polyvinyliden fluoride (PVDF) is knows to be the most suitable piezoelectric material Nanowire and Carbon nano tubes are also suitable for piezoelectric applications 32
Energy Harvesting Material Applications of Textile-based Piezoelectric Material Human Powered Wearable Devices Modern electronic devices require only a few mw of power Human motion would be sufficient for providing power to those devices (Stamer, 1996) Electricity from the change in the chest circumference due to respiration (Zieba (2010), Wang (2012)) Driving a pace maker using blood pressure and heart beat Electricity from heel-attached piezoelectric material (Kymissis, 1998) Piezoelectric energy harvesting device for finger joints and elbow (Yang, 2012) 33 Energy Harvesting Material Applications of Textile-based Piezoelectric Material Military Applications Light weight energy devices is required Even flexible solar cells cannot be used without sun Piezoelectric energy harvesting can be continued in the dark Medical Applications Uninterrupted power supply is required ECG (electrocardiogram), sleep monitoring, breast cancer detection underwear, etc. Energy harvesting is the most desirable solution considering the weight of battery 34
From Body Temperature Energy Harvesting Material Human body generates a few mw of heat energy Micro heat-electricity converter can harvest those energy Usually made by expensive bismuth telluride semi conductors and unsuitable for wearable devices Silicon based flexible chip can be considered to be an alternative material Heat-Electricity converter chip should be integrated into fabric itself To obtain maximum temperature difference between inner and outer surface of the chip One surface faces the body and the other surface faces the outer air Generates about 1.6µW/cm 2 of electricity, which is sufficient to power a wrist watch 35 Laser-Cut Fabric PCB Fabrication Process More Issues A heat activated adhesive is attached to a conductive fabric and covered with a paper Place this fabric, paper side up, into a laser cutter where a circuit pattern is etched The adhesive and paper backing are cut, but the fabric is only scored Once the circuit is cut, the backing paper is removed from underneath the circuit The circuit is then carefully aligned on its fabric substrate and ironed into place 36
Laser Cut Fabric PCB Solder Joint Treatment e-textile Component Fabric PCBs are subject to abuses such as the twisting, folding and stretching of cloth Solder joint must be covered with an inflexible coating to prevent possible breakage 37 Insulation Importance e-textile Component Electrical traces may come in contact with one another as a fabric flexes Traces on textiles must be insulated and protected to prevent short circuits The insulation must preserve the qualities of the textile - soft, flexible, and stretchy Couching Embroidery Iron-on Patch Puffy Fabric Paint 38
Flexible-Stretchable Electronics e-textile Component Fundamental requirements for electronics to be integrated into clothing Many promising demonstrations have surfaced There is no real go-to solution up to now Viable Solution Using a zig-zag stitch for conductive lines between electronic components sewn onto textiles The robustness of this technique is not that great Additional layers of fabric is needed for wear and wash protection 39 String Battery e-textile Component LG Chem Li-Ion battery in string form just a few millimeter thick Bendable and can even be knotted without compromising it s battery function A reasonable power supply completely integrated in garments and bags. 40