title: Force versus axial deflection of pipette-aspirated closed membranes.
abstract: The axial deformation of a pipette-pressurized fluid membrane bag produces minuscule yet well-defined, reproducible forces. The stiffness of this ultrasensitive force transducer is tunable and largely independent of the constitutive membrane behavior. Based on a rigorous variational treatment, we present both numerical as well as approximate analytical solutions for the force-deflection relation of this unique biophysical force probe. Our numerical results predict a measurably nonlinear force-deflection behavior at moderate-to-large deformations, which we confirm experimentally using red blood cells. Furthermore, considering nearly spherical membrane shapes and enforcing proper boundary conditions, we derive an analytical solution valid at small deformations. In this linear regime the pressurized membrane bag behaves like a Hookean spring, with a spring constant that is significantly larger than previously published for the biomembrane force probe.
authors.affiliation: Department of Biomedical Engineering and Biomedical Engineering Graduate Group, University of California, Davis, California 95616, USA. vheinrich@ucdavis.edu
authors.forename: Volkmar
authors.initials: V
authors.lastname: Heinrich
authors.forename: Chawin
authors.initials: C
authors.lastname: Ounkomol
mesh_terms: D000268:Adhesiveness; D001696:Biomechanical Phenomena; D055592:Biophysical Phenomena; D001703:Biophysics; D002462:Cell Membrane / Q000502:physiology*; D004548:Elasticity; D004910:Erythrocyte Membrane / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D011312:Pressure; D013396:Suction; D014159:Transducers