Presented are the methods and experimentally obtained images of a roasted seaweed snack under magnification via a Foldscope. This exercise was performed as part of Stanford’s BIOE 301C: Diagnostics Devices Lab.
Methods. A Foldscope was obtained and assembled using the typical procedure. To hold the sample, the paper slides with rectangular windows (Fig. 1) was used. The seaweed used for experiments was Trader Joe’s Wasabi Roasted Seaweed Snack.
To mount the seaweed sample, a small (~ 2 x 2 mm) strip of seaweed was placed on a clear adhesive strip. The strip itself was bonded to a paper slide (Fig. 2). Finally, an additional paper slide (used as a spacer) was placed on top of the original slide and mounted on the Foldscope (Fig. 3).
To obtain images, the magnetic disk was bonded (via double sided adhesive) to the telephoto lens of an iPhone 11 Pro (Fig. 4). The telephoto lens allows greater zoom-in into the field-of-view enabled by the Foldscope. Hence, better images can be obtained. One challenge, however, is that the default iPhone camera software does not allow selection of this specific lens. The Ullman Indirect app allows selection of the telephoto lens as well as some other convenient features for free.
Results. The resulting images show, with surprising resolution the components of the seaweed. Most distinctively, we can see the presence of sharp walls (demarcated by the dark regions) which likely correspond to cell walls (Figs. 5 and 6).
Surprisingly, the roasted and salted seaweed appears to retain a lot of cellular complexity when inspected by the Foldscope. This indicates that the seaweed cells are tough and at least somewhat resisting to the drying and roasting process. More images are shown below (Figs. 7 and 8). The dark spots on the seaweed may be attributable to flakes of salt.