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MicroscopyEducation


procedure [ 25 ]. T en a critical question was posed to the students: “What can we learn from these cross-sectional images?” Students had many excellent responses including learning about how the brain works and studying diseases (for example, Alzheimer’s disease). Additional uses of the FIB were also discussed in terms of how circuits are produced on computer chips, at which time students were encouraged to use the hand-held magnifying glasses on their desks to observe examples of circuits from older Intel microprocessors. Tomography . In the fi nal activity, the students sliced and imaged a red potato and were shown how multiple 2D images can be compiled into a volumetric data set. T e students fi rst created alignment markers by skewering two central points in the red potato. T en they used the mandolin slicer with a safety guard and Kevlar cut-resistant gloves to cut 2.5 mm thick slices. T e students aligned the slices against an illuminated background and used a phone camera placed on a fi xed stand to take the consecutive slice images. T e images were then downloaded through a Google Drive App on the smartphone and sent to the facilita- tor’s laptop preloaded with ImageJ, which was used for image processing.


Discussion


Figure 4 : Images of Swiss cheese: (a) an individual slice on a sheet of paper, (b) entire cheese block after slicing and reassembly, (c) 3D reconstruction of the Swiss cheese with three cut-aways along the z -axis, and (d) represen- tation of the hole distribution within the Swiss cheese.


spectrum, many students were able to guess “electrons,” which naturally transitioned the discussion onto how an SEM works. T e students were then asked to hypothesize what the SEM might be used to image, and they were shown a short video about examining an insect wing sample in the SEM. Seeing inside . To introduce the FIB, the class was asked how they could see the inside of an object, such as a brain, if the SEM produced only surface images. Exhibiting more confi dence in their hypotheses and increased enthusiasm, many of the students responded “Cut it open!” Facilitators then showed students SEM images from a recent study of a cross- sectioned synaptic connection of a rat brain [ 24 ], and discussed with them how individual slices can be obtained using a microtome or a FIB. T e latter discussion was accompanied by display of an animation that explains the typical FIB-SEM


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While themed around microscopy, this activity introduced the students to a variety of interdisciplinary concepts and thus could be adapted to work with activities centered around other topics. With some additional soſt ware development, an opportunity might arise for combining the described


3D imaging procedure with 3D printers, increasingly popular in K–12 settings. An example might include introduction of students to 3D tomography along with “scaling up” via 3D printing of a dataset of interest obtained with a FIB-SEM (for example, internal components of a cell for biology classes).


Conclusion


We introduced an experimental methodology for performing macroscale “destructive tomography” of common foods, which can be used as a hands-on activity for K–12 students. T e sets of collected 2D images can be processed into volumetric data sets using, for example, ImageJ or Mathematica. We demonstrated our procedure on several foods including a red cabbage, Swiss cheese, and, in a brief in-class activity, a red potato. We also developed an example educational activity that incorporated this destructive


www.microscopy-today.com • 2017 September


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