A Fine Measurement Machine

Integrating Nanotechnology into

the K-12 STEM Curriculum

Rob Snyder: snyder@umassk12.net

In spite of their different goals, science and technology have become closely, even inextricably, related in many fields. The instruments that scientists use, such as the microscope, balance, and chronometer, result from the application of technology/engineering........

Page 8: http://www.doe.mass.edu/frameworks/scitech/1006.doc

Atomic Force Microscopes (AFMs) are used Atomic Force Microscopes (AFMs) are used to make nanoscale measurementsto make nanoscale measurements

This is an AFM at the Center for Hierarchical Manufacturing at the University of Massachusetts Amherst.

An AFM generated this image of the An AFM generated this image of the ionic crystal lattice array of sodium chloride.ionic crystal lattice array of sodium chloride.

http://en.wikipedia.org/wiki/Image:AFM_view_of_sodium_chloride.gif

Mark Tuominen is the Co-Director of the CHM at UMass Amherst

In this demonstration, he uses a laser pointer to show how an AFM uses a reflected beam of light to make nanoscale measurements.

Key features of an AFM include:Key features of an AFM include:

A flexible cantilever that exerts a small amount of A flexible cantilever that exerts a small amount of downward force on an object so that the object is not downward force on an object so that the object is not damageddamaged..

A mirror that creates a long pathway for reflected light A mirror that creates a long pathway for reflected light to travel so that the motion of the tip at the and of the to travel so that the motion of the tip at the and of the cantilever is multiplied.cantilever is multiplied.

This was our first attempt to have students model the process of making measurements

with an AFM.

This design was based on an article that appeared in the December 2006 issue of Science Teacher.

Our “beta” version made use of a simple first class lever.

A lever measurement device has a A lever measurement device has a number of components.number of components.

Laser PointerRuler

Lever supportmirror

Hanging mass

A students activity document A students activity document provides directions for:provides directions for:

• Assembling a lever mechanism that can measure the thinness of an object.

• Calibrating the lever mechanism.• Determining how much the level

mechanism multiplies motion.• Developing a strategy to map an

uneven surface.

If a thin object moves under one end of the If a thin object moves under one end of the lever arm. It causes the lever arm to move a lever arm. It causes the lever arm to move a short distance and a point of light on a wall short distance and a point of light on a wall ruler moves a greater distance.ruler moves a greater distance.

The reflected light beam now reaches a different point on the ruler.

A hanging mass needs to be placed in a A hanging mass needs to be placed in a position on the short arm of the lever so that position on the short arm of the lever so that the end of the long lever arm does not exert a the end of the long lever arm does not exert a

lot of downward force on the object that is lot of downward force on the object that is being measured.being measured.

The lever needs to be able to respond to subtle changes in thinness.

An object of a known thinness can be An object of a known thinness can be used to calibrate the measurement machine.used to calibrate the measurement machine.

The calibration reveals the relationship between the movement of the lever and the movement of the point of light on the ruler.

Shims of know thicknesses can be used to calibrate the measurement machine.

Tasks for team members to accomplish.Tasks for team members to accomplish.

• Organize a work area.• Coordinating your group’s movements

with other groups.• Assembling the machine.• Managing the experimental procedure.• Working with the laser pointer

carefully.• Collecting and recording data.• Keeping the lever assembly stable.

Students have an opportunity to assemble a device.

Activities like this can build a problem solving team approach as students manage the

experimental process.

Students can develop a s strategy for measuring the angles of incidence and reflection.

Angle of Incidence

Angle of Reflection

Normal Line

ruler

A reflected beam of light needs to be located on a scale and its movement

needs to be measured carefully.

Data needs to be recorded and analyzed.

Mathematical relationships can be discovered.

.cantilever

laser

Long light path and a short cantilever gives large amplification

d1

d2

L1

L2pivotpoint

The distance amplification d2/ d1 is proportional to L2/ L1

Students can explore how extending the path of light affects the measurement process.

ruler

Another Mirror Ruler

A Balanced Torques activity document explores an important aspect of a lever mechanism.

Point of Rotation

This activity includes calculating the weight of the hanging mass and the mirror.

A few examples of assessment questions

How was the fine measurement machine similar to How was the fine measurement machine similar to and different from the design of an actual Atomic and different from the design of an actual Atomic Force Microscope?Force Microscope?

How do you know when the fine measurement machine reaches an equilibrium?

Why do we need to minimize the amount of Why do we need to minimize the amount of downward force acting on an object being mapped?downward force acting on an object being mapped?

What forces are involved when the model of an AFM is mapping an object?

How would you change the design of the fine measurement machine to make it more effective?

An AFM has even been transported to Mars.

This image presents data from the AFM on NASA's Phoenix Mars Lander. It shows surface details of a substrate on the microscope station's sample wheel. It will be used as an aid for interpreting later images of minuscule Martian soil particles. Source: http://www.nasa.gov/mission_pages/phoenix/images/press/First_AFM_on_MARS.html