We investigate the role of substrate surface energy on the removal of triacylglycerol (TAG) films by a model surfactant solution under laminar flow conditions. We select a mixture of 0.5:0.3:0.2 triolein:tripalmitin:tristearin
mass fraction as a model TAG, yielding a solid ‘fat’ film, and expose it to a micellar aqueous surfactant solution,
flowing at rate 250 μLmin−1
(corresponding to a velocity of 1.4 cms−1
), within a microfluidic channel. We
employ a combination of optical and atomic force microscopy, profilometry, X-ray photoelectron and infrared
spectroscopy, and contact angle measurements to characterise a range of model substrates, the TAG films,
and their removal over time. Our experimental data show a clear dependence of the TAG removal time with
surface energy and, in particular, with the polar component of the surface energy, 𝛾𝑆𝐹 𝐸
𝑃
. TAG films on very
hydrophilic surfaces, with high 𝛾𝑆𝐹 𝐸
𝑃
(> 20 mJ/m2
), are generally found to delaminate rapidly, while those on
lower 𝛾𝑆𝐹 𝐸
𝑃
surfaces are progressively eroded over longer timescales. An approximately inverse linear relation
is found between 𝛾𝑆𝐹 𝐸
𝑃 and removal time 𝜏, which holds for a large range of surfaces including glass, silicon
and plastics, and various surface treatments.