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The artificial nose project

Micrometer-sized resonating cantilevers are used to measure the molecular components of exhaled air, to diagnose your health condition.
The topic of this week is the development of an electronic nose, also called the e-nose. We will discuss how nanotechnology can be used to obtain information from actual breath. Knowledge about the composition of the exhaled air provides much information about your health. Then we’ll describe so-called cantilever devices. This is technology we use to determine composition of breath. We will explain what a cantilever is, how it can be used as a sensor, and how it is made. We all know and maybe even have used a very common test for the composition of exhaled air– the alcohol breath test. The police uses such a breath tester to check if you did not drink too much before driving.
In such a handheld electronic instrument, a simple electrochemical reaction takes place between the alcohol and the chemical in the tester. This reaction is used to measure the amount of alcohol in your exhaled air which is related to the amount of alcohol in your blood. But the exhaled air contains many more different gases. Of course there is carbon dioxide and water as well as unused air, but also small amounts of many other gases that are produced by your body. The composition and amounts of these gases may tell something about your body. Would it not be wonderful if you could realize a handheld device that can detect your medical condition simply by sniffing your breath.
Therefore we want to realize an artificial nose. For that, we need to be able to measure many components of the exhaled air. is the topic of this week– how to tackle this technological challenge. First we discuss why one would like to analyze breath apart from testing for drunkenness. We describe the composition of air you exhale and what it can tell the doctor. Then we shift the focus to technology. How can micro and nanotechnology help to determine the composition of air? We will explain what cantilevers are and how we can use them to measure gas composition. After design comes fabrication. We will describe the steps of a possible fabrication route for cantilevers starting with a bare silicon wafer.
In the cleanroom, many different techniques are used to fabricate devices with micrometer and nanometer dimensions. This week we will describe how patterns are defined by a process called photolithography. In the next two weeks, we will discuss how these patterns are used to make structures. The development of a new technology is only one side of the story. We end this week’s session with a discussion of a few ethical or societal questions that may arise when a new technology is introduced– questions that you may not have thought of before. Next to that, there are issues that influence a successful introduction of a new technology in society.
In the end, a producer of new diagnostic tools needs to make a business out of it.

The analysis of your breath can provide much information about processes going on in your body and especially in your lungs. The alcohol breath test is a well-known test, checking for only one component in the exhaled air, namely for alcohol. However your breath contains dozens of different molecules that are the product of biochemical reactions taking place in your body.

This week we explain why information about these molecules is important. Then we discuss how nanotechnology can help to measure these molecules in your breath. The technology we employ to do that is based on so-called micro-cantilevers.

We explain how these work and can be used for gas measurements. Then we describe how they are made in the clean-room, going through all the process steps.

One of several technologies, that are used in the fabrication of nano-devices in general and of cantilevers in particular, is the photolithography process. It is explained how this process is used to define structures on the micrometer and nanometer scale.

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Nanotechnology for Health: Innovative Designs for Medical Diagnosis

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