RESUMO
A novel microtensile testing instrument was developed to assess the mechanical properties of small-diameter polyethylene, polyurethane, and polyester microfibers. The instrument had a root-mean-square error of 2.96 microN for force measurement and 1.91 microm for displacement measurement. Microfibers ranging in diameter from 1.0 to 10.9 microm were strained at 2 mm/s in the device, and the slopes of their stress-strain curves (material moduli) were determined. Correlations between material modulus and previously published data on fibrous capsule presence and thickness for implanted polyethylene, polyurethane, and polyester microfibers were investigated. Results for the 1.0-5.9-microm microfiber diameter range showed that neither the percentage of unencapsulated fibers nor the capsule thickness correlated well with modulus. Correlation coefficients were 0.04 and 0.09, respectively. However, for the 6.0-10.9 microm diameter range the correlations were strong, 1.00 for both percentage of unencapsulated fibers and capsule thickness. It is suggested that the results reflect the greater attachment and mechanical interaction of cells with microfibers for the 6.0-10.9 microm-diameter range than for the 1.0-5.9 microm-diameter range.