Measuring Wettability of Biosurfaces at the Microscale
Determining the contact angle of a liquid on a solid surface is a simple method to assess the surface wettability. The most common method to measure the contact angle of a liquid consists of capturing the profile of a sessile drop of a few microliters on the surface using an optical system. Currently, this is a widely used technique to analyze wettability both in researched materials and in products of multiple technological fields. However, the drop dispensed by a traditional macroscopic contact angle meter is too big to assess the wettability properties of individual topographical features and/or chemical patterns at the micro/nanoscale. Recently, contact angle meters that can discharge drops that are microscopic, with volumes in the range of 1 × 10−3 to 10−5 μL have been developed. The novel microscopic contact angle meter uses a pneumatic injection system to discharge the drop of the liquid through a capillary of a few micrometers of internal diameter and a high-resolution ultrafast digital camera.
We have tested different biosurfaces – microimprinted polymers for biosensors, calcium-phosphate cements with different topographical microfeatures, orthodontic wires – and assessed the potential applicability in the field in comparison with the conventional macroscopic contact angle meters.
This protocol describes the basic tasks needed to test wettability on biosurfaces with a microscopic contact angle meter. The focus of the protocol is on the challenging methodological steps and those that differentiate the use of this equipment to the use of a traditional macroscopic contact angle meter.
Key wordsMicroscopic contact angle Wettability Biosurface Biomaterial
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