Imagine Imaging

Participants slide a magnetic probe across a flat flexible magnet to discover a bumpy pattern. While the bumps are undetectable to sight and touch, the push and pull of the probe across the magnet are easily felt. Invite participants to use this feature to align puzzle pieces within the magnet and compare their experience to the way chemists use scanning probe microscopy to learn about the arrangement of atoms on the surface of a sample.

Ages
11 and up

Activity Time
Preparation: 5 minutes
Activity: 5–8 minutes

Group Size
Number of participants:
1 person per magnet

Ratio of facilitators to participants:
1 facilitator for every 2 participants

The ACS Committee on Community Activities and Office of Science Outreach presents Imagine Imaging: A Magnetic Analogy for Scanning Probe Microscopy

Vimeo ID: 1008459682

Concepts to Explore

  • Flat flexible refrigerator magnets are made of ferrite crystals sealed in plastic. The ferrite crystals are arranged to create a magnetic field that is strong on one side of the magnet and weak on the other side.
  • While the surface of the magnet feels smooth, the arrangement of the ferrite crystals can be detected with another flat flexible magnet or a magnetic field viewer.
  • Scientists and engineers invent and use tools to observe things beyond what our senses can see, hear, and feel.
  • Scanning probe microscopy (SPM) allows people to observe the arrangement of atoms at the surface of a solid.

Safety Requirements & Other Considerations

  • Safety glasses are appropriate for this activity.
  • Keep magnets away from electronics and data storage devices.
  • Conduct your own RAMP assessment prior to presenting the activity. 
Download RAMP Worksheet (PDF)

Question to Investigate

Can you complete a refrigerator magnet puzzle when all the pieces are face-down?

Materials Required

Per participant:

  • One custom ACS Imagine Imaging magnet or at least two flat flexible refrigerator magnets
    How to acquire an ACS Imagine Imaging magnet:
    • Available at the ACS store; ACS member price is $9.00 for 10 magnets
  • Various magnets such as a bar magnet, ring magnet, or cow magnet
Postcard-sized flat flexible magnet with three smiling emoji wearing safety glasses, each within a different kiss-cut shape—a pentagon, triangle, and heart.

Per table:

  • Magnetic field viewer with colors indicating strength in Gauss
  • Graph paper or a striped, gingham, or grid tablecloth
  • Optional:
    • Steel cookie sheet or magnetic white board with sample flat flexible magnets or other types of magnets on them.
    • Images of AFM renderings, optional
  • Any additional materials identified in your RAMP analysis

Preparation

Prior to Activity

Prepare Materials

  • Test your magnets ahead of time. Flat flexible refrigerator magnets will vary in how well they work. This may be due to the size of the units in the Halbach array or degradation of the magnetic field. Most magnets are printed either horizontally or vertically. Note that some shapes may be printed at an angle to maximize the number that can be printed on each sheet of flat flexible magnet.

On-Site

  • Arrange two or four stations across the front of a 6- or 8-foot rectangular table. One facilitator can support two stations comfortably.
  • Place one Imagine Imaging magnet or a few rectangular flat flexible magnets at each station.
  • Place the magnetic field viewer and any additional magnets near the facilitator(s).

Instructions & Talking Points

  • Introduce flat flexible magnets and how they only stick to steel on one side

    Instructions

    Tell participants:

    • Flat flexible refrigerator magnets stick to each other or to steel. The graphic side does not stick to steel. This is not normal! Regular magnets stick to steel, no matter which way you position them.

    Talking Points

    • Do you have any flat flexible magnets at home?  
    • Are flat flexible magnets broken on one side? 
    • Does the sticker side “block” the magnet’s attraction to steel?
      Probably not, because you can hold a couple pieces of paper or stickers onto a piece of steel with the magnet side.

  • Have participants feel the magnet with their fingers first and then with the magnetic probe

    Instructions

    Direct participants to:

    • Place the magnet face-down to explore the side that is attracted to steel.
    • Slide your fingers over the “back” of the magnet.
    • Left-to-right (L-R) or right-to-left (R-L)
    • Top-to-bottom (T-B) or bottom-to-top (B-T)
    • Next, slide the magnetic probe over the “back” of the magnet.
    • L-R or R-L
    • T-B or B-T
    • Flip the magnet over so that it is “face-up.” Slide the probe over the “front” of the magnet.

    Talking Points

    • Does the surface of the magnet feel smooth or rough?
      Smooth
    • What do you notice when you slide the magnetic probe across the magnet?
      It feels like there are bumps only when you swipe across, not in any other direction. 
    • The bumps are kind of like speed bumps that go across a road or ripples on water. What direction do you think the “speed bumps” are going compared to the lines on the graph paper or tablecloth?

  • Introduce the magnetic field viewer

    Instructions

    Show participants:

    • Place the magnetic field viewer over various regular magnets.
    • Place the magnetic field viewer over the “back” and “front” of the flat flexible magnet. 

    Talking Points

    • How is the shape of the magnetic field of a flat flexible magnet different from that of a regular magnet?
    • Do you see the same pattern in the magnetic field of both sides of flat flexible magnet?

  • Compare the experience using the magnetic probe to chemists inventing and using scanning probe microscopy 

    Instructions

    Tell participants:

    • You correctly observed the parallel lines before you saw them. 
    • Then you used the magnetic probe to figure out something that your senses of sight, hearing, and touch could not notice.
    • When scientists can’t observe properties with their senses of sight, hearing, and touch, they invent tools and techniques to help them make observations.
    • Chemists use a tool called scanning probe microscopy (SPM) to make an image of the atoms on the surface of a sample. They can also use SPM to move atoms around. 
    • The probe is so sharp that there is just one single atom at its tip.
    • The probe either taps or slides across a sample.
    • Then the computer draws a 3D graph that chemists can see!

  • Place the puzzle and pieces face-down mix them up and solve the puzzle

    Instructions

    Direct participants to:

    • Place the magnet face down and remove all the pieces so that they are also face down.
    • Mix up the pieces.

    Tell participants:

    • The heart will fit only one way, the triangle will fit three ways, and the pentagon five ways.
    • Your challenge is to figure out which direction to place each shape so that the “lines” of the magnetic field go the same way as the rest of the magnet! 

    Talking Points

    • Are the chemoiji lined up?
      Maybe
    • What makes the  triangle and pentagon more challenging to place than the heart?
    • Can you complete this puzzle while keeping all the pieces face-down

  • Use the magnetic probe to feel the direction of the “speed bumps” to help solve the puzzle

    Instructions

    Direct participants to:

    • Try doing the puzzle face-down using the magnetic probe.
    • Slide the probe L-R or R-L across the heart and from T-B or B-T
    • Slide the probe parallel to each flat edge of the triangle and pentagon to find the direction with the “speed bumps.”

    Talking Points

    • How will you know which direction to place each piece in the puzzle?  

  • Place the magnetic field viewer on the puzzle to check the direction of the magnetic field on the pieces. 

    Instructions

    • Allow participants to use the magnetic probe and field viewer to align any pieces where the “lines” are going in the wrong direction. 

    Talking Points

    • Do you think that the pieces are aligned with the rest of the magnet?

  • Flip the puzzle over to see  the chemoji

    Instructions

    • Use the magnetic field viewer to help flip the puzzle over. 

    Talking Points

    • Do you feel successful?

  • Compare the experience with the magnet to SPM

    Instructions

    Tell participants:

    • When scientists can’t observe properties with their senses of sight, hearing, and touch, they invent tools and techniques to help them make observations.
Students performing the Imagine Imaging activity at an event
The back side of the Imagine Imaging flat flexible magnet.
Magnetic strength card demonstrating how to approximate the strength of a magnetic field.
Your magnetic field viewer may come with a card that interprets the colors seen on the magnetic field viewer as a range of gauss to approximate the strength of the magnetic field.

Clean Up

  • Reset for more participants by ensuring that the pieces are in place and the entire magnet is face down on the graph paper, tray, or table. Return the magnetic field viewer to the facilitator. 
  • At the end of the session, collect the completed magnets and magnetic field viewers. 
  • Fold and reuse the tablecloth and collect the graph paper for future science or math activities.  

Explore the Chemistry

How are refrigerator magnets made?

To make a sheet of flat flexible magnet, manufacturers heat ferrite crystals and plastic until the plastic melts. They mix them together well and then pour the mixture into a thin layer. While still wet, they bring a strong magnet close to the sheet. This magnetizes the ferrite crystals and moves them into a particular arrangement called a Halbach array. As the plastic cools, it locks the ferrite crystals in place.

Why doesn’t the printed side of a flat flexible magnet stick to steel?

The Halbach array arranges each crystal so that magnetic north points in a repeating pattern of left-up-right-down. This strengthens the magnetic field on one side and nearly cancels it out on the other. This is why flat flexible refrigerator magnets will slip off a piece of steel when placed graphic-side-down. It also means that manufacturers can use less ferrite to get a magnetic field that is strong enough to stick to steel, even with a couple of sheets of paper in between. The first Halbach array was designed to focus the beams of a particle accelerator. Now there are many other useful applications, including refrigerator magnets, aerospace applications, and certain locking systems!

How do scanning probe microscopes work?

Scanning probe microscopy (SPM) allows people to observe atoms at the surface of a solid at the nanoscale level. SPM was originally invented to see the atoms in a sheet of silicon. Optical microscopes require light. Because silicon atoms are smaller than the smallest wavelength of visible light, the inventors had to discover a different way to detect atoms. Scientists invented a type of SPM now called the scanning tunnelling microscope (STM) in 1981 and, in 1986, were awarded the Nobel Prize for it.

The tip of the probe of an SPM is so sharp that it is just one single atom thick. A lever holding the probe moves in response to the electron cloud surrounding each atom at the surface of the sample. Changes in the electron field of the atom on the probe tip are measured. The data collected is used to determine coordinates which when compiled appear as an image on a computer screen.

This is how scientists and engineers visualize the way atoms are arranged at the surface of a sample. SPMs allow scientists and engineers to research electronics, materials science, microbiology, and data storage.                              

Volunteer doing the Imagine Imaging activity with students

References

Download Instructions [PDF] PDF version of instructions for this activity