Specimen Capsules For Critical-Point Drying

Extract

Since we do a lot of small-sample critical-point drying (CPD) for SEM, we assemble our own drying capsules which can be manufactured easily in quantity. Materials' cost at current prices is about $10 for 50 capsules. About 25 capsules can be manufactured in an hour. The completed capsule consists of a small polypropylene chamber with fine-mesh, stainless-steel screen caps at each end that allow easy exchange of solvents. shows the steps ofthe assembly process. The base of one capsule is cut off with a razor blade, the cap of a second capsule, for a bottom (Figure 1a). Chamber length can be 5 to 14mm. One-quarter-inch holes are punched through the center of each cap using a paper punch whose spring/detente has been removed to pass the caps' rim (Figure 1b). A sheet-metal shim punch is used to create 3/8" disks of 60-mesh stainless steel wire cloth.