Guest Blog by Kevin Yapps.
Kevin has taught in various Science settings. His current role is teaching French Immersion Sciences as well as a combined French Science-Math option at WL Seaton Secondary Vernon, BC. Kevin is an avid tinkerer and maker and loves incorporating it into his Science instruction. @yappsolutely
Osmosis: abstract and difficult to demonstrate
For years, I have been trying to come up with concrete methodology that will help learners better understand osmosis. Laboratory exercises and online videos have made it much simpler to understanding diffusion. However, I have always found it daunting to come up with activities that make it easier to understand osmosis because it almost seems counter-intuitive.
A colleague shared a lab-activity with me where students used red onion epidermis. Students were instructed to do a classic wet-mount slide preparation. Then, with the use of a pipette, they injected a saline solution between the slide and the slide cover. All this was to be executed in real-time with the prepared slide on the stage: talk about complicated! Even when or if it worked, it was difficult for the untrained eye to understand what it was looking at.
Let’s just say that the students, like always, loved the fact that they were doing “lab-work,” but they executed it without fully knowing whether or not it worked. I was left having to explain what they should be seeing. A student mentioned that everything happened too fast. This made me reflect. I didn’t want to throw the activity out. It had so much potential.
How it all came together: the “a-ha moment”
I began to reflect on the activity. What went well? What went horribly wrong and what needed to be improved? About a week prior to this activity, students were encouraged to use their smartphones during lab-work to snap photos of pond life through the microscope. This was a very engaging activity for students and they were proud to share, via Airdrop or email, the various photos and videos of microorganisms (I even began to archive these in a Google Photos photo album). A collective problem with this technique was finding a way to hold the phone still to take a photo. Some used 2 sets of hands! Then, they had to crop out the impertinent segments of their photos.
I thought to myself: “If only there was a way to hold the cameras to take better photos. I could 3D-print a mounting apparatus! Photos will be clear and I can even take video like I would with a tripod.” Using a 3D printer was not a viable option for me at that point, so I began to improvise with selfie-sticks and “oogoo” (silicone and cornstarch). Let’s just say that my prototypes were marginally functional.
Then, one evening, while surfing aimlessly on the Interweb, I stumbled upon a DIY microscope video from the Instructables website: a home-made microscope that used a small acrylic lens coupled with the focusing power of a smartphone camera. Subsequent Youtube searches yielded demonstrations; one of them being with red-onion cells. I immediately concluded that this project could solve my previous problems with camera stillness and videos. To boot, I had also come to the realization that time-lapse was a function that existed on most new smartphones.
I now had a way to watch the phenomenon in real-time, in time-lapse and then repeatedly by using video. For example, once salt water is injected into the cellular matrix, cytoplasm leaves the cells to balance the exterior. In real-time, this is difficult to notice as it happens over minutes. Time-lapse permits the observer to watch 5 minutes-worth of footage in a few seconds. Moreover, the time-bar in the video application permits the observer to go back and forth in time. If you miss something, it’s always accessible! Having the luxury of going over the visual component of osmosis with learners is a very powerful tool. (The following photo’s were all taken using these microscopes.)
*3x 4 ½” x 5/16” carriage bolts
*9x 5/16” nuts
*3x 5/16” wing nuts
*5x 5/16” washers
**¾” x 7” x 7” plywood — for the base
***⅛” x 7” x 7” plexiglass — for the camera stage
***⅛” x 3” x 7” plexiglass — for the specimen stage
****11/32 inch threaded Acrylic lens (use two for increased magnification)
*****LED click light (necessary only for viewing backlit specimens)
*Can be found at any hardware store – It is better to buy from a wholesaler to cut costs
**I use old shelving – You will need a saw to cut this with the appropriate dimensions
***I found used plexiglass in the school. Canvassing your local glass retailers for donations (even scrap pieces work)
****I found small acrylic lenses on Amazon
***** LED lights can easily be found at any hardware stores
Use the Instructables website if you are uncomfortable troubleshooting on your own. You will need the following tools and accessories for building purposes:
- Drills bits – 5/16 (to drill through wood)
- Step-drill bits (to drill through plexiglass)
- Table saw and or Mitre Saw
- File (to soften edges on plexiglass after cuts)
Potential related projects and cross-curricular
There is the potential to collaborate with a visual-arts class. Students can share their photos with collaborating arts students who can transform microscopy photos into works of art. This could work well with pond life organisms, insects, etc.
If you are not comfortable using small power tools in your classroom (i.e. drills and saws), you can converse with your school’s tech-ed instructor. High school and middle school shops usually possess the necessary tools.
Every semester, I have students use previous classes’ home-made microscopes. They use the “Design Thinking” methodology to establish a plan to build a 2.0 version.