After assembling my foldscope, my first impulse was to take a drop of my blood and image it. Sadly, the result was not as good as I expected.
Blood is a very complex fluid, it packs a large amount of cells, and a thick sample as the one I imaged is going to produce a bad image. Light is coming from everywhere in the sample, and the image will be very blurry.
My second attempt came after reading this post: http://microcosmos.foldscope.com/2015/01/14/experiments-with-blood/
First, I need a very thin sample, just one cell thick. In order to get it, I put a drop of blood on a coverslip, and with a second coverslip I smeared the blood. And the result is strikingly good. In order to check the progress, I covered the smeared sample with a second coverslip, sealed it, and had a look under the microscope. And surprisingly, I was able to see the Red Blood Cells!
The Red Blood Cells are clearly visible and their biconcave shape is apparent.
Then, I decided to go a step further, fix the cells and stain them. I went around the house, and the most promising staining that I found was iodine. Iodine is an antiseptic, present in most medicine cabinets. It has a deep red color, and it reacts with starch and sugars, changing to a purple-blue color. My hope was that, if it attaches to membranes and structures, it would remain redish, and if it attaches to nuclear material, it would turn bluish. So, I fixed the sample with 95% ethanol. After 5 minutes, I rinsed it several times with water. I covered the sample with 1% iodine solution, and rinsed it again several times with water. I covered the sample with a second coverslip and sealed it. When imaging the sample so treated, I get clearly distinguishable pale-red Red Blood Cells (sorry if the color is not so apparent in the pictures), but unfortunately, no nuclei, so I was not able to see any white blood cells.