The modified pendent drop technique

A recently developed modification of the pendent drop method gives definite area changes of the drop surface, which can be used to initiate transient relaxation processes (Miller et al. 1993a, b). A metering system consisting of two syringes (cf Fig. 6.7) is used to form a drop 

In this way transient relaxation experiments with any type of area disturbances are possible. The high resolution and excellent accuracy of better than 0.1 mN/m provides a useful tool for studies of dynamics of soluble adsorption layers. The method can be applied to liquid/gas as well as liquid/liquid interfaces and is easily temperature controlled. Experimental data obtained by this technique on aqueous solutions of surfactants and proteins are given below (Miller et al. 1993a, b, c). 

Very recently this technique was also applied for studies of monolayer isotherms of insoluble surfactants (Kwok et al. 1994) and the dynamic behaviour of insoluble monolayers. In Appendix 6C these investigations are discussed in more detail. 

The drop pressure experiment developed by Nagarajan Wasan (1993), and Horozov et al. 

Wasan et al. (1993) demonstrated different types of surface area changes of surfactant solution drops and the respective surface tension responses. 

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