🔧 Year 9 Design & Technology

Iterative Design

What Is Iterative Design?

• Iterative design: a cyclical process of designing, prototyping, testing, evaluating, and refining — repeated until the design meets the brief
• Contrast with linear design (design once → make once): iterative design acknowledges that good products are rarely perfect on the first attempt
• Used in product design, software development (Agile methodology), architecture, and engineering

The Design Cycle

• Investigate: research the context, user needs, existing products. Define the problem. Write a design specification (criteria the product must meet).
• Design: generate multiple ideas (don't just go with the first idea). Use sketching, mood boards, CAD. Select the most promising and develop it.
• Prototype: make a physical or digital model to test your ideas. Early prototypes should be quick and cheap (cardboard, foam, simple CAD renders).
• Test and evaluate: test against the specification criteria. Involve real users. Identify what works and what needs to change.
• Refine: return to the design stage with what you've learned. Repeat until the product meets the specification.

Design Specifications

• A design specification sets out measurable criteria the final product must meet
• Good specifications are SMART: Specific, Measurable, Achievable, Relevant, Time-bound
• Categories to cover: function, aesthetics, size/scale, materials, cost, safety, sustainability, user group, manufacturing
• Example: "The product must support a minimum load of 5kg" is better than "the product must be strong"

Product Analysis

Why Analyse Existing Products?

• Analysing existing products (commercial or historical) teaches you what works, what doesn't, and what problems need solving differently
• Good designers are aware of precedents — you don't need to reinvent the wheel, but you should know what wheel exists

ACCESSFM Framework

• Aesthetics: does the product look appealing? What visual qualities does it have? Colour, form, finish, proportion.
• Cost: how much does it cost to make (cost of goods)? What is the retail price? Is it value for money?
• Customer / Client: who is the intended user? How does the design serve their needs?
• Environment: how sustainable is the product? Where does it come from? What happens to it at end-of-life?
• Size: what are the dimensions? Are they appropriate for the user and function?
• Safety: are there any hazards? How are they mitigated? What testing and certifications apply (CE mark, etc.)?
• Function: what does it do? How well does it perform its function? Are there secondary functions?
• Material: what is it made from? Why was that material chosen (properties, cost, availability, sustainability)?

New & Smart Materials

What Are Smart Materials?

• Smart materials: materials that respond to changes in their environment (temperature, light, stress, electricity) in a predetermined, useful way
• They are increasingly important in product design, architecture, medicine, and wearable technology

Key Smart Materials

• Shape Memory Alloys (SMAs): return to their original shape when heated. Nitinol (nickel-titanium alloy) is the most common. Used in: medical stents, orthodontic braces, spectacle frames, robotic actuators.
• Thermochromic materials: change colour with temperature. Used in: mood rings, temperature-sensitive labels, coffee cups that show when a drink is hot, novelty materials.
• Photochromic materials: darken when exposed to UV light, become transparent in the dark. Transition lenses in spectacles. Self-tinting window glass.
• Piezoelectric materials: generate electricity when mechanically stressed, or change shape when an electric current is applied. Used in: ultrasound transducers, microphones, speakers, energy harvesting from vibrations (floors that generate power from footsteps).
• Quantum tunnelling composite (QTC): is an insulator when uncompressed but becomes a conductor when compressed. Used in pressure-sensitive switches.
• Graphene: a single layer of carbon atoms in a hexagonal lattice. Stronger than steel, highly conductive, flexible, nearly transparent. Potential applications: ultrafast transistors, flexible displays, supercapacitors, water filtration membranes.

Modern Manufacturing Materials

• Carbon fibre reinforced polymer (CFRP): very high strength-to-weight ratio. Used in aerospace, Formula 1, high-end bicycles. Expensive to produce.
• Aerogel: the world's least dense solid. 99.8% air. Excellent thermal insulation. Used in NASA spacesuits and polar expedition gear.
• Biomaterials: materials grown from living organisms (mycelium packaging, bacterial cellulose leather alternatives). Sustainable and biodegradable.

Sustainability in Design

The Six Rs of Sustainability

• Rethink: question whether the product is necessary at all. Is there a more sustainable way to meet the user need?
• Refuse: refuse to use unsustainable materials or processes; design against planned obsolescence
• Reduce: use less material in the product; reduce packaging; reduce energy use in manufacturing
• Reuse: design for reuse — refillable containers, modular products, durable materials
• Recycle: design products so their materials can be separated and recycled at end-of-life
• Repair: design for repairability — accessible fasteners, available spare parts, clear repair instructions. Right to Repair legislation gaining traction.

Life Cycle Assessment (LCA)

• LCA: assessing the environmental impact of a product across its entire life — from raw material extraction to end-of-life disposal
• Stages: raw material extraction → manufacturing → distribution → use → disposal (or recycling)
• "Cradle to grave": extraction → disposal. "Cradle to cradle": materials are recovered and reused at end-of-life — a circular economy approach.
• Embodied carbon: the CO₂ emitted in making a product before it is ever used. For some long-lived products (buildings), embodied carbon is larger than operational carbon.

Circular Economy

• Linear economy: take → make → dispose. Resources extracted, made into products, used, and thrown away.
• Circular economy: keep materials in use for as long as possible. Products designed to be maintained, repaired, remanufactured, and ultimately recycled. Waste is designed out.
• Examples: Patagonia's "Don't Buy This Jacket" campaign (repair culture); Interface carpet tiles (designed for disassembly, tiles recycled into new tiles); Renault's remanufacturing of car parts.

Systems & Control

Systems Thinking

• A system: a set of components that work together to achieve a function
• All systems have: inputs (what goes in), processes (what happens), and outputs (what comes out)
• Open-loop system: no feedback. A toaster (set a timer; no check on whether the toast is done)
• Closed-loop system: feedback from the output is used to adjust the input. A thermostat (temperature measured → compared to set point → heater switched on or off)

Electronic Systems in Products

• Input transducers (sensors): convert physical quantities into electrical signals. Light dependent resistor (LDR), thermistor, microphone, pressure sensor, moisture sensor.
• Process: the electronic circuit or microcontroller that processes the sensor signal and makes a decision
• Output transducers (actuators): convert electrical signals back into physical action. LED, motor, speaker, solenoid, buzzer.
• Microcontrollers (Arduino, Raspberry Pi, BBC micro:bit): programmable processing units that can read sensors and control outputs. Allow very sophisticated control with relatively simple code.

The Internet of Things (IoT)

• IoT: everyday objects connected to the internet and to each other, able to send and receive data
• Examples: smart home (Alexa, Nest thermostat, Hue lights), smart meters, wearables (Apple Watch monitoring heart rate), connected cars
• Design considerations: security (IoT devices have been exploited in cyber attacks), privacy (what data is collected and by whom?), energy use (millions of always-on devices), interoperability (will products work together?)