US Patent 11951470 Dual differential displacement fluid metering

The present disclosure provides better aspiration and dispensing of fluids by an innovative mechanism by (i) offsetting the diameter of a bottom tube with a narrower top piston when the two are moved together in the same chamber to give extremely fine resolution, thereby eliminating the need for any skinny or filamentous piston, (ii) letting the bottom tube move in the chamber alone without offset to give high flow, (iii) an at-the-ready space between the tube and piston in the chamber to permit contact-free blowoff, including viscous samples, and (iv) a frame, adjustable knob and readable volume gage that let the mechanism operate as a handheld pipettor apparatus for various volumes.