Cantilevered-Capillary Force Apparatus for Measuring Multiphase Fluid Interactions

Abstract

A new instrument is presented for investigating interactions between individual colloidal particles, emulsion droplets, foam bubbles, and other particle-particle or particle-surface interactions. Measurement capabilities are demonstrated by measuring interfacial tension, coalescence time for emulsion droplets, adhesion between giant multilamellar vesicles, and adhesion between model food emulsion particles. The magnitude of the interaction force that can be measured or imposed, ranges from 1 nN to 1 mN for particles ranging in size from 10 μm to 1 mm in diameter.

Micropipette force sensors for in vivo force measurements on single cells and multicellular microorganisms

“…To this day, micropipette force sensors have been used to directly probe for example cell mechanics [43,44] and force generation [45], the elasticity of chromosomes [2,46,47,48], the interfacial tension of micrometer-sized droplets [49], the strength and breakup of flocks [50,51], the tensile strength of biofilms [51], the adhesion of single bacterial cells [52], the tension of an elastomer film [53], as well as electrically tunable wetting properties [54]. In a further development of the technique, called "cantilevered-capillary force apparatus" (CCFA), the glass micropipettes were exchanged by less fragile but thicker and stiffer glass capillaries that typically are used as columns for gas chromatography [55]. Due to the higher stiffness of the capillaries, these have a force resolution of ~1 nN which is two orders of magnitude higher than MFS.…”

“…A learning period of 3-6 months is to be expected to reach such an expert level. Mastering the MFS technique to its full extent opens exciting research avenues and allows for pushing the force sensitivity limits, where the highly sensitive glass micropipettes provide a force resolution that is two orders of magnitude better than the capillaries used in CCFA [55] and a signal-to-noise ratio that is comparable to force measurements using AFM.…”

Direct measurement of interaction forces between charged multilamellar vesicles†

“…The resolution of the interaction force that can be detected is about 1 nN in the present work. A full description of the instrument can be found in a separate paper [13].…”

“…The present work uses a new instrument called a Cantilevered-Capillary Force Apparatus (CCFA) [13] that enables direct force measurements between two vesicles at approach and separation velocities that are sufficient to expose dynamic (non-equilibrium) effects on adhesion/de-adhesion. This is a first step toward understanding the interactions of vesicles in suspension that is undergoing a flow.…”

Mapping coalescence of micron-sized drops and bubbles

“…This includes the liquid surface forces apparatus [14], the work from the Horn group using a modified surface force apparatus using a mercury [15,16] or gas [17] filled capillary and a rigid flat surface, and the extension of atomic force microscopy (AFM) to probe the interactions between, first, a rigid particle and a single bubble [18][19][20] or drop [21][22][23][24], and secondly, to measure the interactions of drop [25][26][27] or bubble [28] pairs. There have also been more recent developments, including the integration of interferometry with AFM to probe a single bubble with a flat surface [29], larger length-scale systems that utilise bimorph cantilevers and a single drop or bubble in the integrated thin film drainage apparatus (ITFDA) [30], and cantilevered capillaries to examine the interaction of two drops [31]. The range of surface forces examined in these experiments include Derjaguin-Landau-Verwey-Overbeek (DLVO) forces (the addition of electrical double layer and van der Waals) [25,32,33], repulsive van der Waals forces [34,35], steric [36,37], structural [36,38,39], depletion [36,40], protein interactions [36,41] and hydrophobic forces [42].…”