Abstract:
Accurate measurement of contact angles can define
fluid dynamics, surface material properties and contribute to
the development of micro/nanofluidic devices. The drop shape
analysis technique was developed to accurately determine the
contact angle and surface tension of a liquid drop on a solid
surface. The technique involves capturing a reflected image of the
drop profile, acquiring coordinate points along the contour and
finding the mathematical best-fit accordingly. Many conventional
equipment utilizes this method through manual acquisition and
analysis of data. This is an arduous, time consuming task which
can introduce inaccuracies. Nevertheless, partially automated
equipment can be prohibitively expensive. Here its shown that
by utilizing embedded system development techniques, both the
imaging and profile analyzing tasks as well as the liquid dispenser
can be automated and precisely controlled by a computer
application at a fraction of the cost of a commercial unit. The
developed system also facilitates sample stage tilting which can
provide information on dynamic liquid profiles to determine
advancing and receding contact angles. Importantly the device
is capable of dispensing and analyzing less than 5 nl volumes of
liquid. Such measurements are becoming increasingly important
in the understanding of areas such as superhydrophobicity and
microfluidic devices.
