Inkwell

Current manual smearing methods lack consistency and often do not provide a uniformly dense mono-layer of red blood cells, even when prepared by trained experts. Existing devices for assisting in making thin smears are available but are limited by cost or complexity for wider use. Here we present Inkwell, a portable mechanical device capable of making high quality thin blood smears in field settings. Inkwell is simple, low-cost, does not use electricity, and requires minimal training prior to use. By utilizing passive dissipative dynamics of a spiral spring coupled to an air dashpot with a tunable valve - we demonstrate a highly tunable mechanism for constant velocity smears at prescribed angle. Inkwell is capable of producing high quality blood smears of tunable cell density with more than 12 million individually distinguishable red blood cells on a single slide.