Measurement of viscoelastic particle deformation using pipette ion currents

Abstract

Ion pipette aspiration (IPA) is a technique for measuring the mechanical properties of soft microparticles. This method combines the principles of micropipette aspiration (MA), which uses optical images to observe particle deformation, and resistive pulse sensing (RPS), which uses the ion current passing through a pipette tip. It is important to better understand the relationship between these two data streams for advanced applications such as nanoscale or high throughput measurements, which would remove reliance on optical microscopy. Here, IPA has been used to investigate polydimethylsiloxane (PDMS) microparticles in a comparative study with atomic force microscopy (AFM), an established material characterisation technique. The IPA apparatus provides data resolution that is unprecedented for this type of experiment. A correlation between the mechanical properties derived using conventional MA and the corresponding ion current measurement was established. Subsequently, the mechanical properties of particles deforming through micropipettes could be predicted with good agreement using a regression model built upon the observed relationship. IPA can be used to study bioparticles and should find applications in the field of mechanobiology.