Versatile horizontal force probe for mechanical tests on pipette-held cells, particles, and membrane capsules

We present a multipurpose nanomechanical force probe that combines a sideways-mounted elastic cantilever and an optical-lever detection module with automated micropipette manipulation. It allows us to apply and measure compression, stretching, adhesion, and dissociation forces in the horizontal direction while providing a "side view" of ongoing experiments. The integrated micropipette setup facilitates the easy manipulation and mechanical interrogation of individual cells, functionalized particles, and synthetic membrane capsules. Pipette-held test objects are translated perpendicularly to and from the stationary cantilever, eliminating the need to attach them to a carrier surface and substantially reducing unwanted hydrodynamic coupling effects. Moreover, the test objects can be brought into contact with the cantilever anywhere along its length, which considerably enlarges the range of forces that can be applied with a single cantilever. Advantages of this instrument are demonstrated in example measurements of single-cell compression, membrane-tether extrusion, oligonucleotide stretching, and extraction of individual lipids from surfactant-monolayer surfaces of microbubbles.