Smart Materials

Smart Materials

• materials that change physical or mechanical properties (color, shape, or resistance) in response to environmental changes (temperature, light, moisture, pressure, or electricity)

• changes are temporary and reversible, material returns to previous state once intialising environmental factor is removed

Examples of Smart Materials

- Electroluminescent Material

- Quantum Tunnelling Composite (QTC)

- Shape Memory Alloys (SMAs)

- Polymorph

- Photochromic Pigment

- Thermochromic Pigment

- Micro-encapsulation

- Biomimetics

Electroluminescent Material

- EL wire, made from a thin copper core coated in phosphor powder, glows when exposed to alternating electrical current

- color depends on phosphor pigment

- EL wire is flexible → use in decorative lighting, signage, clothing, films or panels (cannot generate heat, replace LCD displays) in mobile phones, car dashboard displays, watch illumination

Quantum Tunnelling Composite (QTC)

- flexible polymers where, when pressure is applied, conductive nickel particles in it make contact and change from insulators to conductors

- used in variable speed controllers, membrane switches, mobile phones, and pressure sensors

Shape Memory Alloys (SMAs)

- returns to original shape if heated

- used in medical fastening in bone fractures and dental braces (reacts to body heat, keeps wire under tension, prevent loosening)

- Example: Nitinol (alloy of titanium and nickel)

Polymorph

- thermoforming polymer becomes soft and pliable when (re)heated in water at 62°C, solidifies when cooled → can be machined and shaped with hand tools

- use for modelling ergonomic product features in schools

Photochromic Pigment

- changes colour in response to light intensity

- use in sunglasses → lens darkens or lightens in response to the UV radiation

Thermochromic Pigment

- change color in response to heat, can be designed to react at specific temperatures (range)

- use in baby bath thermometers, food indicators, and drink labels → show when specific temperature reached

Micro-Encapsulation

- application and release (through friction with skin) of microscopic capsules (containing substances like moisturisers, and antiseptics) to fibres, fabrics, paper and card

- use in wound dressing → antiseptics → direct contact with wound to heal and reduce potential infection, sportswear → chemicals → repel odour and prevent fungal infections

Biomimetrics

- inspiration for new fabrics comes from the natural world, mimicking natural situations.

- Fastskin, developed by Speedo for performance enhancing swimwear, mimics the shark's natural sandpaper-like skin, reducing water drag

Composites

- combining two or more materials to create an enhanced material with their individual properties

- consist of a matrix and a reinforcement (or fibre)

Examples of Composites

- Carbon Fibre Reinforced Polymer (CFRP)

- Glass Reinforced Plastic (GRP)

Carbon Fibre Reinforced Polymer (CFRP)

- high-performance composite made from woven carbon fibre strands with high tensile strength in lightweight, rigid polymer resin

- use in racing and mountain bikes, Formula 1 parts, sports equipment, and aerospace → excellent strength-to-weight ratio, stiff, and can produce streamlined shapes

Glass Reinforced Plastic (GRP)

- composite of glass fibres and polyester resin

- cheaper, easier to manufacture, less visually appealing pigmented finish than CFRP

- resin provides toughness and lightness, glass fibres add rigidity

- used in boats, canoes, hockey sticks, and car body work.

- irreversible when cured, difficult to recycle

Kevlar

- trade name for durable, high-tensile strength, lightweight, flexible, heat and chemical damage resistant fibre developed by DuPont

- use in police body armour → woven lattice protects against knife attacks

- fibre component in resin-based composites

Technical Textiles

engineered with specific performance characteristics that suit a particular purpose or function

Examples of Technical Textiles

- Interactive Textiles

- Microfibres

- Phase-changing Materials

- Breathable Fabrics

- Rhovyl

- Sun-protective Clothing

- Nomex

- Geotextiles

Interactive Textiles

- fabrics embedded with user-interactive electronic devices or circuits

- use conductive (carbon, steel or silver) fibres and threads woven or sewn into product to form circuits

- performance/heart-rate monitor in athelete's shirt (monitors performance and fitness levels), GPS trackers, and communication devices (mobile phones)

Microfibres

- very fine synthetic fibres made from polyester or nylon

- lightweight, water-resistant, breathable, excellent strength-to-weight ratio

- use in cleaning cloths (attract dust and dirt effectively), fabric printing (clear image definition)

- Examples → Tactel® and Tencel™ (Lyocell)

Phase-Changing Materials

- encapsulated droplets on materials that absorb, store, and release heat energy by changing between liquid and solid states within a specific temperature range

- micro-encapsulated into textiles or applied as coatings to create thermo-regulating fabrics

- use in clothing (manage body temperature)

- Example → Outlast® fabric, originally for space use

Breathable Fabrics

- breathable, waterproof, and windproof fabrics let warm air and small moisture droplets from perspiration pass through, blocking larger rain droplets and wind

- use in high-performance clothing and footwear (regulates body temperature)

- Example: Gore-Tex, three or more fabrics laminated together with a breathable membrane inbetween

Rhovyl

- synthetic fibre from polyvinyl chloride (PVC)

- non-flammable, crease-resistant, good thermal, acoustic, and antibacterial properties, waterproof, dries quickly, wicks away moisture through the fabric (easy to care for), durable, odour-resistant, soft and comfortable when spun and woven into fabric

- use in clothing, high-performance sportswear

Sun-Protective Clothing

- effectiveness depends on the tightness of fabric's knit or weave, reduce gaps between yarns, blocking more UV radiation

- fabrics with elastane minimise spaces, enhancing protection

- synthetic fibres (polyester and nylon) → natural lustre reflect UV rays

Nomex

- aramid synthetic fibre (heat-resistant, non-flammable, and strong) developed by DuPont

- combined with Kevlar to create a lightweight composite with high strength-to-weight ratio → use in aircraft construction (Airbus 380), improves fuel efficiency

- use in firefighter uniforms, racing suits, oven gloves, and fire-resistant insulation on buildings

Geotextiles

- woven or bonded, synthetic or natural, permeable fabrics

- can filter, separate, protect and drain

- orginally for use with soil, use in civil engineering, road and building construction, maintanence