Try Your Hand at Nano

Try Your Hand at Nano

Lesson Focus

This lesson focuses on two simple activities younger students can do to gain an appreciation for nanotechnology. First, students measure their hands in nanometers, second students learn about liquid crystals, their applications and nanotechnology connections, and test how the heat of their hands changes the color of the crystals. They observe what they see, present their findings to the class, and reflect on the experience. 

Lesson Synopsis 

The “Try Your Hand at Nano” lesson shows younger students how small a nano really is and introduces the concept of how elements may change behavior at smaller sizes — for example, liquid crystals change their behavior and their color when exposed to different temperatures. Students work in teams to measure their hands in nanometers, and test a liquid crystal sheet. Teams review their experiences, present their findings to the class, and reflect on the experience. 

Age Levels 

8-11.

Learning Objectives 

• Learn about nanotechnology. 
• Learn about liquid crystals. 
• Learn how engineering can help solve society’s challenges.
• Learn about teamwork and working in groups. 

Anticipated Learner Outcomes 

As a result of this activity, students should develop an understanding of: 

• nanotechnology 
• liquid crystals 
• electricity
• teamwork. 

Lesson Activities 

 Students explore nanotechnology through a measurement and temperature exercise involving liquid crystals. They learn about liquid crystal applications, and how size can impact how a material behaves. Student teams consider their experience, present to the class, and reflect on the experience. 

Resources/Materials 

• Teacher Resource Information 
• Student Resource Information 
• Student Worksheets (included here) 

Alignment to Curriculum Frameworks 

See the included curriculum alignment information. 

Internet Resources 

• TryEngineering (www.tryengineering.org) 
• TryNano (You’re already here!) 
• National Nanotechnology Initiative (www.nano.gov) 
• Liquid Crystals (National Science Foundation uTube) (www.youtube.com/watch?v=nAJgchCI3kg) 
• Liquid Crystal Introduction – McGill University (http://barrett-group.mcgill.ca/tutorials/liquid_crystal/LC02.htm).

Supplemental Reading 

• Nanotechnology For Dummies (ISBN: 978-0470891919) 
• Science at the Nanoscale: An Introductory Textbook (ISBN: 978-9814241038)
• Liquid Crystal Displays: Fundamental Physics and Technology (Wiley Series in Display Technology) (ISBN: 978-0470930878)

Optional Writing Activity 

Write a paragraph about how liquid crystal displays have impacted how we watch television. 

For Teachers: 

Lesson Goal 

The “Try Your Hand at Nano” lesson shows younger students how small a nano really is and introduces the concept of how elements may change behavior at smaller sizes — for example, liquid crystals change their behavior and their color when exposed to different temperatures. Students work in teams to measure their hands in nanometers, and text a liquid crystal sheet. Teams review their experiences, present their findings to the class, and reflect on the experience.  

Lesson Objectives 

• Learn about nanotechnology. 
• Learn about liquid crystals. 
• Learn how engineering can help solve society’s challenges. 
• Learn about teamwork and problem solving. 

Materials 

• Student Resource Sheet 
• Student Worksheets 
• Class Materials: Liquid crystal sheet size 20cm x 20cm roughly (available from Amazon, and many science and educator supply services) 
• Student Team Materials: ruler, pencils, paper. 

Procedure 

1. Show students the student reference sheets. These may be read in class or provided as reading material for the prior night’s homework. 
2. To introduce the lesson, consider asking the students how large their hand would be in nanometers. 
3. If internet access is available, have students review the resources at www.trynano.org. The site will provide additional background information about nanotechnology and the industries where it is having great impact. 
4. Activity 1: Have students hypothesize and then actually measure their hand in nanometers, centimeters and inches. Have students compare the actual number with their hypotheses and consider how small a nanometer is. 
5. Activity 2: Review sheets about liquid crystals and their applications, then have students take turns putting their hand on a large liquid crystal sheet and observe what happens. Student teams make hypotheses and then test what happens when they put various items on top of the sheet: their hand, an apple, an ice cube or cup of cold water. 
6. Teams observe what happened, compare their hypotheses to the actual results, complete a reflection sheet, and present their experiences to the class.

Time Needed 

One or two 45-minute sessions.

For Students: 

What is Nanotechnology? 

Imagine being able to observe the motion of a red blood cell as it moves through your vein. What would it be like to observe the sodium and chlorine atoms as they get close enough to actually transfer electrons and form a salt crystal or observe the vibration of molecules as the temperature rises in a pan of water? Because of tools or ‘scopes’ that have been developed and improved over the last few decades we can observe situations like many of the examples at the start of this paragraph. This ability to observe, measure and even manipulate materials at the molecular or atomic scale is called nanotechnology or nanoscience. If we have a nano “something” we have one billionth of that something. Scientists and engineers apply the nano prefix to many “somethings” including meters (length), seconds (time), liters (volume) and grams (mass) to represent what is understandably a very small quantity. Most often nano is applied to the length scale and we measure and talk about nanometers (nm). Individual atoms are smaller than 1 nm in diameter, with it taking about 10 hydrogen atoms in a row to create a line 1 nm in length. Other atoms are larger than hydrogen but still have diameters less than a nanometer. A typical virus is about 100 nm in diameter and a bacterium is about 1000 nm head to tail. The tools that have allowed us to observe the previously invisible world of the nanoscale are the Atomic Force Microscope and the Scanning Electron Microscope. 

How Big is Small? 

It can be hard to visualize how small things are at the nanoscale. The following exercise can help you visualize how big small can be! Consider a bowling ball, a billiard ball, a tennis ball, a golf ball, a marble, and a pea. Think about the relative size of these items. 

Scanning Electron Microscope 

The scanning electron microscope is a special type of electron microscope that creates images of a sample surface by scanning it with a high-energy beam of electrons in a raster scan pattern. In a raster scan, an image is cut up into a sequence of (usually horizontal) strips known as “scan lines.” The electrons interact with the atoms that make up the sample and produce signals that provide data about the surface’s shape, composition, and even whether it can conduct electricity. Many images taken with scanning electron microscopes maybe viewed at www.dartmouth.edu/~emlab/gallery. 

Nanoscale Properties 

Properties of materials at the nanoscale are different in many cases from the properties of materials observed in other scales. Consider, for example, the melting temperature of metals. Nanoparticles often exhibit a lower melting temperature than the corresponding metals in bulk, and these temperatures depend on size. For example, bulk gold melts at 1064 degrees Celsius, but a 4nm gold particle melts at roughly 850 degrees Celsius. 

The color of a material can also depend on size. The appearance of color is caused by the partial absorption of light by electrons in that material; the unabsorbed part of the light remains visible. 

On most smooth metal surfaces, light is entirely reflected by the very high density of conduction electrons; this is why the surfaces of slabs of metal have a mirror-like appearance. In contrast, small particles absorb some of the light, leading to the appearance of color. This behavior depends on size. 

For example, gold exhibits a different color depending on its particle size. Extremely tiny particles of gold have been used to colored glasses since the very early days of glass making. Ruby vases (with color that is pink to blood-red) were made using finely dispersed gold particles for centuries. Many stained glass windows exhibit red color because of doping with gold nanoparticles. 

Nanosystems are not large enough for many classical laws of physics to apply. For example, Ohm’s law, which describes the relation between current and voltage in a conductor, does not describe current conduction through a tiny nanowire. Here other effects, known as quantum mechanical effects are more important.

Liquid Crystals 

Liquid crystals (LCs) are in a state of matter that has properties between those of a usual liquid and those of a solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are a few different types of liquid crystals, but thermotropic liquid crystals change their properties as the temperature changes. If you apply something hot (like your hand) to an encased liquid crystal sheet, it will change color according to the temperature variation. The colors shift from red to orange to yellow, then green, blue and purple as the LCs get hotter! 

How is this Nano? 

Changes in a material’s structure are usually too small to view directly, but often we can instead observe changes in the material’s properties as a result of the structural changes. Thermotropic liquid crystals change color when exposed to different temperatures — so we see the color property change even though we cannot observe in a classroom the change in their molecular structure. The liquid crystals change color as a result of adjustments in the arrangement of their molecules at the nanoscale. In nanotechnology, scientists take advantage of the peculiar properties of materials at the nanoscale to engineer new materials and devices. 

Thermometer Applications 

Liquid crystal color transitions are used in sheets on many aquarium and pool thermometers as well as on thermometers for infants or baths. Other liquid crystal materials change color when stretched or stressed. Liquid crystal sheets are often used in industry to look for hot spots in a manufacturing process, or to map the flow of heat. 

Liquid Crystal Displays 

A liquid crystal display (LCD) is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals (LCs). LCs do not emit light directly. LCDs are used in many products such as computer monitors, televisions, instrument panels, gaming devices, clocks, watches, calculators, and telephones.