Final Design

Figure 1. Picture of Final Design 

Component 1: Slide Transportation Mechanism

Figure 2. Transportation mechanism top view w/ annotation

●      C-beam linear actuator. The linear actuator with its speed controlled by Arduino, transports the slide holder from one end to the other, as shown in Figure 2.

●      Slide holder. It can hold two slides at a time. Friction tape and clamps are used to increase the friction on the slides.

●      Stepper Motor. The core of the C-beam linear actuator, which is a NEMA 23 stepper motor controlled by a micro-step motor controller for precise position control. 

Component 2: Straw Pressing Mechanism

Figure 3. Straw pressing mechanism

●      Rack and Pinion. Rack and pinion are used to transform the rotational movement of the motor to linear motion of the pushing surface.

●      Pushing Surface. This 3D printed part shown in Figure 8 makes sure the force applied on the straw to be uniform.

●      Supporter. The supporter helps to constrain the rack so that it can only move in the vertical direction, as demonstrated in Figure 3.

●      Straw Stopper. Holds the straw above the slide before smearing and provide an adjustable gap for straws with different diameters. The straw would be pushed down and squeezed into the gap to touch the slide for smearing. After the completion of smearing, the straw will be pushed through the gap and fall into the disposal box.

Component 3: Straw Loading and Disposal Mechanism

Figure 4. Straw loading and disposal mechanism

●      Straw Dispenser. This ramp stores and loads the straws.

●      Straw disposal box. The used straws are stored in the straw disposal box.

Workflow

The final design has the capability to produce two quality blood smears each time the user put two slides with a blood drop on each of them. Figure 5 below demonstrates the workflow of the whole smearing process.

Figure 5. System workflow diagram

Initially, the operator places two empty Sysmex slides on the slide holder. The operator can set the velocity of transportation, the displacement of the rack and adjust the distance between the stopper and straw dispenser based on the selected straw diameter. The operator needs to apply one blood drop on each of the slides. Then, the device starts to transport the slide to the smearing position under the straw. The rack begins to press the straw allowing blood drop to form into a line following the curvature of the straw. The transportation system moves back to the starting position and achieves smearing. The rack presses the straw down to the disposal container to finish the whole process.