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
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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).


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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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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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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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2.11 Storage

In a given fixed space at any phase of the hydrological cycle, there is an inflow and an outflow of water, the rates of which vary with time. The total cumulative difference between inflow and outflow is the storage. So within that space there is a body of water whose mass is not directly controlled by instantaneous values of inflow and outflow. For example, in river flow the movement of the whole body of water in the channel is generally downstream, yet a given reach contains a volume whose
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1 Some facts about water

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