To measure the failure force under a transverse load, a row of 5–10 microneedles was mounted vertically on a metal plate using epoxy adhesive (Pacer Technology, Rancho Cucamonga, CA). To apply the transverse load, a glass slide was prepared
by bonding a PDMS film (110.5 cm) with cyanoacrylate adhesive Products, Columbus, OH) to the glass slide to make
a stepped structure. The PDMS film extended 500
Am beyond the edge of the glass slide to provide a
surface of defined dimensions. Using the force
displacement–force test station, the PDMS extension
from the glass slide was pressed perpendicular to the
microneedle axis against a 500 Am length of the
microneedle shaft starting at the needle tip. As
shown in Fig. 4(C), needle force and displacement
were continuously measured until the needles were
broken, as verified by microscopy.