posted on 2021-08-27, 18:04authored byYiwen Xi, Prashant Kumar Sharma, Hans Jan Kaper, Chang-Hwan Choi
The
applications of hydrogels in tissue engineering as implants
have rapidly grown in the last decade. However, the tribological properties
of hydrogels under physiologically relevant conditions, especially
those of textured hydrogels, have remained largely unknown due to
the complexity of their mechanical and chemical properties. In this
study, we experimentally investigated the tribological properties
of micopored poly(2-hydroxyethyl methacrylate) (pHEMA) with the lateral pore dimensions
varied compared to untextured pHEMA, the most commonly used hydrogel
in ophthalmology, under physiologically relevant conditions. The pHEMA
specimens were slid against a smooth glass curve under varying loads
(6–60 mN, leading to an average contact pressure of 10–21
kPa) and sliding speeds (1–10 mm/s) in phosphate-buffered saline
(pH 7.4) at 33 °C to mimic the physiological conditions in human
eyes. At relatively low loads and sliding speeds (e.g., 6 mN and 1
mm/s), the micopored pHEMA did not reduce the dissipated frictional
energy significantly. However, at relatively high loads and sliding
speeds (e.g., 60 mN and 100 mm/s), the micopored pHEMA resulted in
significantly lower frictional energy (reduced by up to 68%) dissipation
than the untextured pHEMA. The effect was more pronounced with the
micropores with smaller dimensions. These are attributed to the greater
amount and retentivity of the interfacial fluid supported by the free
water squeezed out of the micropores with the smaller dimensions under
the higher load and sliding speed. These results suggest that the
use of micropore texturing on hydrogels in practice, such as for ocular
applications, can be leveraged to reduce friction and wear under physiological
conditions and hence lower the chance of inflammation near eye implants
or keratoprosthesis.