You can distinguish U-2D™ inserts (used vs. unused) by one of the following ways:
A. Used samples can be indicated on the silicone mat/film using a marker.
B. Alternatively, the film or mat can be cut with scissors to an appropriate size to protect unused inserts or to help keep track of used inserts.
C. Users can selectively remove unused (or used) inserts as needed. Inserts should be carefully handled/stored to prevent contamination prior to use or transfer.