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
to 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
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:
A flexible cantilever that exerts a small amount of
downward force on an object so that the object is not
damaged.
A mirror that creates a long pathway for reflected light
to travel so that the motion of the tip at the and of the
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
number of components.
Ruler
Laser Pointer
Hanging mass
mirror
Lever support
A students activity document
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
lever arm. It causes the lever arm to move a
short distance and a point of light on a wall
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
position on the short arm of the lever so that
the end of the long lever arm does not exert a
lot of downward force on the object that is
being measured.
The lever needs to be able to respond to
subtle changes in thinness.
An object of a known thinness can be
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.
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•
•
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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.
Normal Line
Angle of Reflection
ruler
Angle of Incidence
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.
Long light path and a short cantilever gives large amplification
laser
d2
pivot
point
L2
cantilever
d1
L1
The distance amplification d2/ d1 is proportional to L2/ L1
.
Students can explore how extending the path of
light affects the measurement process.
Another Mirror
ruler
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
and different from the design of an actual Atomic
Force Microscope?
How do you know when the fine measurement
machine reaches an equilibrium?
Why do we need to minimize the amount of
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_AF
M_on_MARS.html