5.7 Being ethical

As outlined in Table 2, ethics within systemic practice are perceived as operating on multiple levels. Like the systems concept of hierarchy, what we perceive to be good at one level might be bad at another. Because an epistemological position must be chosen, rather than taken as a given, the choi
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1 Putting the unit in context

This unit, taken from T883 Business operations: delivering value, is concerned with the management of ‘processes’ – the organised set of resources and related activities that are essential for the delivery of goods and/or services to customers. These processes or ‘operations’ form the very essence of any enterprise, and it is critically important that they are managed well to be effective and efficient.

The full course consists of three main blocks of study:

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8.2 Wet etches: acids and bases

The simplest etches use a liquid solvent that converts the material into a soluble compound or a gas. Unfortunately, most materials used in micro-devices have few soluble compounds, so some very aggressive chemicals are needed to attack them. Here is a list of some of the most commonly used ones:

• Hydrofluoric acid (chemical formula HF) is used to convert silicon dioxide into water-soluble H₂SiF₆ (plus some hydrogen and water). It
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4.2 The piezoelectric effect at the atomic scale

It has been mentioned above that by changing the state of polarisation of a piezoelectric material we can generate movement, and vice versa. Let's examine a little more deeply what is meant by ‘state of polarisation’ and how we can maximise its effect to get the best out of electrically controlled micro-actuators.

In order to electrically polarise a material we need, by definition, to cause a separation of charges within the material. The more we can do this the greater the d
Author(s): The Open University

Introduction

This unit examines how small features can be etched and cut out of solid materials at a very small scale.

This unit is an adapted extract from the Open University course Engineering small worlds: micro and nano technologies (T356).

3.1.2 Shutter

The electronic shutter that freezes the frame for read-out adds more complexity, but can be based on the standard MOS fabrication steps. In effect, at the end of image capture, the charge at each pixel is first switched into another ‘blind’ MOS capacitor that sits in the read-out line for each row, as the middle of the three buckets per pixel. You should have already guessed that the switch is yet another MOS device. Once switched into the read-out line, the row data are isolated from the
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1.2 MOS structures

Carefully designed metal–oxide–semiconductor (MOS) structures are a common building block in digital electronics, primarily intended to form part of a transistor-based switch. However, throughout the active regions of a microelectronic chip there will be secondary MOS structures that arise because metal tracks are insulated from the semiconductor substrate by a layer of oxide; equally careful design is necessary to ensure that these do not form part of a switch. The acronym is a mixture o
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5.1 The development of the bicycle

Section 4 has looked at how we can follow a logical route or map, from the expression of a need, to arrive at possible solutions to a problem. In Sections 5 and 6 we look in more detail at two quite different examples of engineering problems. Our first example is the historical development of the bicycle frame; the second concerns a vital component of a car's airbag system.

The weight of a bicycle frame is a major burden that the cyclist has to bear. There have certainly been times whe
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4.1 The experimental result

One way to establish the speed of sound is to measure it experimentally. That is, one measures how long the sound takes to travel a known distance, and from this works out the speed. The answer turns out to depend somewhat on the prevailing temperature and humidity. At an air temperature of 14 °C the speed is 340 metres per second and at about 22.5 °C it is 345 metres per second. That is a change of speed of less than 1.5 per cent for an appreciable change of temperature. To a reasonable ap
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2.1 The importance of sine waves

For much of the rest of this unit we shall be concerned with the properties of a type of sound wave that when represented as a graph has a characteristic shape known as a sine wave. Figure 1 shows you what a sine-wave graph looks like. For the moment you need not be concerned with what this grap
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3.5 Distinctions about systems practice

A tension has existed throughout the history of Western thought around whether to focus on parts or the whole. The practice that springs from this history carries the same tension. This tension has been particularly visible within science and philosophy for a long time and it gives rise to different approaches. I will be addressing these tensions in Author(s): The Open University

17.3 Choosing appropriate materials and manufacturing process

The choice of materials and manufacturing process for a particular new product is an important aspect of the innovation process. It is not necessarily the case that the materials chosen for the early prototypes of an invention are those best suited for the larger-scale manufacture of the innovation. Choice of materials can affect the performance, quality and economic manufacture of most new products, so it's important to choose wisely.

While inventors and designers usually need to seek
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10.2 Scientific or technical curiosity

Some inventors understand a scientific phenomenon and set about inventing a technological device to exploit the phenomenon.

The invention of the laser grew from the interest of two researchers in studying the structure and characteristics of a variety of molecules. During the Second World War, Charles H. Townes worked on developing radar navigation bombing systems. After the war he had the idea of modifying the radar techniques and using microwaves to study molecular structure. Subseque
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2 New products – old failings

This section introduces product ‘usability’. It offers a case study of a vegetable peeler to illustrate how usability issues exist alongside other important concerns in the product development process.

If you look around high-street or shopping-mall stores, you cannot help but notice the number and variety of new products on offer. This year's washing machine or dishwasher, stylish furniture, multi-feature telephones, audio systems, DVD players, digital cameras and camcorders, all b
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5.11 Plumbo-solvency

Many water supplies in the UK are naturally acidic, and when this type of water is supplied through lead pipes the lead dissolves into the water. Lead pipes are dominant in many older established areas. The Drinking Water Directive has set a maximum admissible concentration of 10 μg 1⁻¹ lead in water, to be achieved by the year 2013. The obvious solution to this problem is to remove all lead piping but this is a costly exercise. As an interim measure, the water l
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5.5 Flotation

An alternative technique to that of sedimentation is flotation. This uses gas bubbles to increase the buoyancy of suspended solids. The gas bubbles attach to the particles and make their effective density lower than that of the water. This causes the particles to rise through the water to float to the top. Flotation may be achieved by several methods but the most effective form is dissolved air flotation. In this process (Figure 27) air is dissolved in water at elevated pressures and then rel
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5.4 Sedimentation

When water has little or no movement, suspended solids sink to the bottom under the force of gravity and form a sediment. You will recall that we discussed a similar process in estuaries, with solids separating from the water. This process is called sedimentation. In water treatment it is used to remove solids from waters which are high in sediment content, and also to remove particles rendered settleable by coagulation and flocculation.

The theory of sedimentation would
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4.6 Tidal rivers and estuaries

Most of the major cities and harbours in the world are located on estuaries. The estuarine ecosystem is a unique intermediate between the sea, the land and fresh water.

A rather precise definition of an estuary is ‘a semi-enclosed coastal body of water, which has a free connection with the open sea, and within which sea water is measurably diluted with fresh water derived from land drainage’. This excludes large bays with little or no freshwater flow, and large brackish seas and inl
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3.5.3 Protozoa

Protozoa are microscopic single cell animals. They utilise solid substances and bacteria as a food source. They can only function aerobically, and in a stream which contains little organic degradable matter they can become a predominant microbial type. They play an important part in sewage treatment where they remove free-swimming bacteria and help to produce a clear effluent.

In an aquatic environment, there are three main types of protozoa:

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