**Exploring at the Nanoscale**

**Lesson ****Focus**

This lesson focuses on how nanotechnology has impacted our society and how engineers have learned to explore the world at the nanoscale. Students participate in hands-on activities to understand exactly how small the nanoscale is, explore how surface area changes at the nanoscale, and work in teams to develop futuristic applications of nanotechnology.

*Lesson Synopsis *

The “Exploring at the Nanoscale” lesson explores how nanotechnology has impacted the world, and how engineers have to consider the ramifications of working at a very small scale. Students work in teams and explore the increased surface area exposed as items are made smaller and smaller. Students examine and measure large blocks of tofu or gelatin, determining the surface area. Then they slice the block into smaller and smaller pieces, exposing more surfaces, and impacting the surface area. Students also explore the size of small, comparing various items to understand how large a nano is. They work as an engineering team to determine a new application of nanotechnology for a product or process of their choice. Teams present concepts and proposals to a group of potential research funders (the rest of the class) and each then vote for the proposal with the most potential. Student teams complete reflection documents.

*Age Levels *

8-14.

**Learning ***Objectives *

- Learn about nanotechnology.
- Learn about scale.
- Learn about surface area.
- Learn about engineering design.
- Learn about teamwork and working in groups.

*Anticipated Learner Outcomes *

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

- nanotechnology
- problem solving
- teamwork.

*Lesson Activities *

Students learn how engineers working at the nanoscale have a greater surface area to work with. Students work in teams to explore increasing surface area as large blocks are cut to multiple, smaller parts. They then explore a challenge of determining how nanotechnology might help engineers improve a product or a process, and present their proposal to the class.

*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)
- Dartmouth Electron Microscope Facility Images (www.dartmouth.edu/~emlab/gallery)

*Supplemental Reading *

- Nanotechnology For Dummies (ISBN: 978-0470891919)
- Nanotechnology: Understanding Small Systems (ISBN: 978-1138072688)

*Optional Writing Activity *

Write an essay or a paragraph about how nanotechnology might impact space exploration.

*For Teachers: *

*Lesson Goal *

The “Exploring at the Nanoscale” lesson explores how nanotechnology has impacted the world, and how engineers have to consider the ramifications of working at a very small scale. Students work in teams and explore the increased surface area exposed as items are made smaller and smaller. Students examine and measure large blocks of tofu or gelatin determining the surface area. Then they slice the block into smaller and smaller pieces, exposing more surfaces, and impacting the surface area. Students also explore the size of small, comparing various items to understand how large “nano” is. They work as an engineering team to determine a new application of nanotechnology for a product or process of their choice. Teams present concepts and proposals to a group of potential research funders (the rest of the class) and each then vote for the proposal with the most potential. Student teams complete reflection documents.

*Lesson Objectives*

- Learn about nanotechnology.
- Learn about scale.
- Learn about surface area.
- Learn about engineering design.
- Learn about teamwork and working in groups.

*Materials*

- Student Resource Sheet
- Student Worksheets
- One set of materials for each group of students
- Block of extra firm tofu or gelatin
- Cutting surface (plastic plate or cutting board)
- Dull knife
- Ruler or measuring tape

*Procedure*

- Show students the various Student Reference Sheets. These may be read in class, or provided as reading material for the prior night’s homework.
- Surface Area Activity
- Divide students into groups of 2-3 students, providing a set of materials per group.
- Explain that students must work as a team to determine the surface area of a block of tofu at various points (whole, sliced in half, quartered, etc.). Students will first measure the full block and determine the surface area, then cut the block in half and determiine surface area, then half again, etc. until there are many tofu blocks of about 1/2 inch in width.

- Nanoscale Applications Activity
- The same group of 2-3 students work to develop a proposal for a new application of nanotechnology.
- Presentations are made to potential research funders (the rest of the class) who vote for the proposal with the most potential.

- Evaluation – Students complete evaluation/reflection sheets.

*Time Needed*

Two to three 45 minute sessions

*Tips *

- For younger students, a spice or sugar coating on the tofu or gelatin can help students visualize how the surface area has increased. Use a small amount of sugar or spice to coat a large tofu block, and then show students how much more sugar or spice is required to coat all the tiny cubes cut from the large block of tofu.
- For older students, incorporate a research period at www.trynano.org to learn more about applications and nanomaterials.

*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.

*What is Surface Area? *

Surface area is the measure of how much exposed area an object has. It is expressed in “square” units. If an object has flat faces, its surface area can be calculated by adding together the areas of its faces. Even objects with smooth surfaces, such as spheres, have surface area.

Surface Area Formulas

The surface area of a cube may be expressed by the formula:

X = 6 x Y x Y

The drawing to the left shows a cube where Y equals the length of each edge. Because it is a cube, all edges are equal in length.

To determine the surface area of the cube, you first have to find out the area of one face. The area of one face is Y x Y or Y^{2}. To find the surface area of the cube, you need to multiply the area of one side by 6. If, for example, Y equalled 10 mm, then the area of one face would be 100 mm^{2} and the total surface area of the cube would be 600 mm^{2}.

The surface area of a rectangular parallelepiped may be expressed by the formula:

X = 2 x A x B + 2 x A x C + 2 x B x C

With a rectangular parallelepiped, the edges are not equal in length…there are three different lengths to be measured. In the drawing, these are represented by A, B, and C. To determine the area of the front rectangle, we’ll need to multiply A x B.

Since there are two surfaces that are this size, we need 2 x A x B as one part of our formula to determine the surface area. We’ll also need to determine the area of the other faces. We’ll need to multiply A x C, and, because there are two of these faces, we need to include 2 x A x C in the full surface area formula. The remaining faces contribute an area of 2 x B x C. If, for example, the length of A equalled 20 mm, and B equalled 10 mm and C equalled 40 mm then:

A x B = 200 mm, so 2 x A x B = 400 mm^{2}

A x C = 800 mm, so 2 x A x C = 1600 mm^{2}

B x C = 400 mm, so 2 x A x C = 800 mm^{2}

So the surface area of the solid is 2800 mm^{2}.

*Why Surface Area Matters *

At the nanoscale, basic properties of particles may vary significantly from larger particles. This might include mechanical properties, whether the particle conducts electricity, how it reacts to temperature changes, and even how chemical reactions occur. Surface area-to-volume ratio changes as particles become smaller. Because chemical reactions usually take place on the surface of a particle, if there is an increased surface area available for reactions, then the reaction can progress more rapidly.