Blog 5

 blog 5 focuses on material selection 

Week 11: Materials for design 

Currently we are in the 4th stage of product design - Prototyping and Product development 

Knowledge of materials is very important to product design. Companies like Apple go through long processes of material selection just to find the perfect material for an apple product like our iPhones. This is necessary because there are plenty of materials available and long processes of manufacturing. Before selecting the material, it is very important to understand the function of a product. Through this, we identify the criteria needed for these needs. For example, a pot is used to contain and cook food. Hence, the body of a pot should have high thermal conductivity to transfer heat from a heating source quickly. In addition to that, it is also vital to evaluate the performance, cost, environmental friendliness as well as the way it looks. 

For CA2 report, part 1: 

Select materials for the teeth and the cover of a polycarbonate baby milk bottle.

Material selection using COWS (Criteria, Options, Weightage, Score) table:

Teat:

		Options
Criteria	Weightage	Rubber	Heat-resistant grade polystyrene	Silicone	Thermoplastic
Non-porous	40%	0	2 2 x 40% = 80%	3 3 x 40% = 120%	1 1 x 40% = 40%
Corrosion resistance	20%	Excellent  3 x 20%= 60%	Good 2 x 20% = 40%	Excellent  3 x 20% = 60%	Good 2 x 20% = 40%
Thermal conductivity	20%	0.5 W/m.K 1 x 20% = 20%	0.159 W/m.k 3 x 20% = 60%	0.2 W/m.K 2 x 20% = 40%	0.163 W/m.K 3 x 20% = 60%
Flexibility (Modulus of elasticity)	15%	0.05GPa 3 x 15% = 45%	2.95 GPa 1 x 15% = 15%	1.90 GPa 3 x 15% = 45%	2.30 GPa 2 x 15% = 30%
Cost	5%	2.09 USD/kg 2 x 5% = 10%	1.8 USD/kg 3 x 5% = 15%	6.60USD/kg 2 x 5% = 10%	2.03 USD/kg 2 x 5% = 10%
Total	100%	135%	210%	275%	195%

The reasoning for criteria:

Non-porous - To prevent bacteria from being trapped in the teat and causing sickness to the child

Corrosion resistance - To ensure that the material does not break down over repeated use

Thermal conductivity - To ensure that when drinking the warm milk, the baby will not burn/scald themselves

Flexibility - To allow for the material to stretch where necessary when in use

Cost - To ensure that the material is economically viable

Cover:

		Options
Criteria	Weightage	Stainless steel - 316	Aluminum	Polypropylene	Thermoplastic
Nontoxic	40%	Non-toxic 3 x 40% = 120%	Mostly non-toxic 2 x 40% = 80%	Safe for humans  3 x 40% = 120%	Safe to use 2 x 40% = 80%
Non reactive	30%	Excellent 3 x 30% = 90%	Good 2 x 30% = 60%	Good  2 x 30%= 60%	Good 2 x 30% = 60%
Thermal conductivity	15%	16.2 W/m.K 1 x 15% = 15%	25 W/m.K 1 x 15% = 15%	0.2 W/m.K 3 x 15%=45%	0.163 W/m.K 3 x 15% = 45%
Lightweight (density)	10%	7.99 g/cm3 1 x 10% = 10%	3.9 g/cm3 1 x 10% = 10%	0.931 g/cm3 3 x 10 = 30%	1.07 g/cm3 2 x 10% = 20%
Cost	5%	4.3 USD/kg 1 x 5% = 5%	2.49 USD/kg 2 x 5% = 10%	1.41 USD/Kg 3 x 5% = 15%	2.03 USD/kg 2 x 5% = 10%
Total	100%	240%	175%	270%	215%

The reasoning for criteria: 

Non-toxic - So that the baby doesn’t get harmed by toxins when drinking from the bottle 

Nonreactive - To ensure that the material does not break down over repeated exposure to milk

Thermal conductivity - lower thermal conductivity will prevent the baby from scalding.

Lightweight - To make sure that the bottle is light enough for an infant to hold 

Cost - To ensure that the material is economically viable

Week 12: Design For Materials

Previously, my group and I did material selection based on cows, feasibility analysis, and literature review which also includes doing surveys and research. This allows us to find materials that can be used for our products, bringing convenience, ease of use, aesthetics, and functionality. 

Some examples of product development: 

1. Hair dryer 

In the past, a hair dryer used to be heavy/bulky, dangerous to use, and does not provide a strong airflow. However, developments of the product had been made and soon the Hawkins supreme hairdryer with lighter and safer materials have been made. In modern-day, the hair dryer has been engineered to become lightweight, safe, and can even be controlled to different airspeeds. With technological advancements, the hair dryer can even be used for styling, prevent hair from extreme heat damage and even improve the looks of users. 

After understanding the developments of products and how engineers improve the manufacturing of different items, we went on to study different materials and completed part 2 of the CA2 report, finding substituting materials for existing products. 

Tritan was the material we selected. This material can be used to replace many items, mainly glass, and hence, we applied it to replace drinking cups material as well as the face of pressure gauges used in the industrial plants as these materials used before are brittle and break easily, whereas using Tritan will prevent that mishap from happening, at the same time, provide the same function (for drinking cup and for reading pressure gauge)

CA2 Report, Part 3: Sustainable Design (10%)

Sustainable design is the approach to creating products and services that have considered the environmental, social, and economic impacts from the initial phase through to the end of life.    What change can be made to your design to make it more environmentally sustainable?   Some design Considerations/Principles are included here: §  Use non-toxic, sustainably produced, or recycled materials. §  Use energy efficient processes. §  Make product last longer. §  Design for reuse and recycling. (e.g. easy to disassemble) §     Consider product life cycle. §  Shift from personal ownership to shared ownership. §    Buy from nearby

What change can be made to your design to make it more environmentally sustainable?   Using wood instead of plastic for insulation as it is biodegradable.   Using solar panels as a source of energy for the heater instead of electricity.   Using a rechargeable battery for the heater so that it doesn’t have to be disposed of when the battery runs out.   Using natural rubber for the handle.   Discuss and document the modification in design or substituting of certain parts of the product or any other ideas that your team has made. You may include pictures and sketches to aid in the explanation   Using wood for the insulation is not that ideal as trees are a finite source. Using wood would cause more trees to be chopped down and damage the environment.   The solar panels are too expensive, and it doesn’t fit in our budget of $2000 and it is not very power efficient.   We will be substituting our power source with the rechargeable battery as it fits our product requirements and does not create risk.   Natural rubber can also be used as it is textile and comfortable to hold.

Practical 3

For practical 3, my group (HongYi, Mavis) and I were tasked to complete experiment 3B, surface tension of water. 

Surface tension is the tendency of the liquid surface at rest to shrink into a minimum surface area before its cohesive forces break. Surface tension decreases when temperature increases.

There are several ways to measure the surface tension of water. Some methods include the Wilhelmy plate, pendant drop, du nouy ring and even a tensiometer. The Wilhelmy plate and du nouy ring are similar in the way the experiment is carried out. With the Du Nouy ring, a ring is used as a probe and is submerged below the surface. The ring is then lifted slowly until the surface of the water tear. This pulling force is then calculated and surface pressure can be computed using the formula, Gamma=Force/length. The Wilhelmy plate uses a similar method, but with a rough platinum plate as a probe instead of a ring. 

In this experiment, we utilized the Du Nouy ring method to measure the surface tension. A lever balance with one end attached to the ring and the other attached to a weighing boat is used. 

The lever is lowered until the ring is submerged just beneath the surface of the water. 

Beads and pebbles are added to exert an anti-clockwise moment on the lever until the surface breaks in which the ring lifts off the surface. 

(image of water surface right before tearing)

Once the water surface tear, the mass of the weight used is then measured using a weighing balance and force is calculated using F=ma before using the gamma formula as mentioned before. 

We repeated the formula 8 times before moving on to add 1 drop of detergent to find out if the addition of detergent will affect the interfacial tension of water. 

Understanding the surface tension of a liquid is important, especially for developing pharmaceutical products. In the real world, the surface tension of detergent is evaluated to determine the efficiency of the detergent formulation. A higher surface tension usually means a relatively poor cleaning detergent and using hot water would likely counter this effect. 

In our experiment, the addition of detergent reduced the surface tension from 0.080613N/m to 0.056207N/m. Throughout the experiment, I personally feel that the weights used to measure the mass the surface can withstand can be improved. Using a smaller weight would give us better control of the surface tension tearing and hence provide a more accurate result.