Final Design

Auto-mech sorting of female mosquito pupae

    The automatic mosquito pupae sorting machine can differentiate the gender in a mosquito pupa and/or larva and transport it into the designated collecting tank. Couple with a water pump, the entire system forms a closed loop for water circulation for water conservation and to prevent biological hazards from going down the drain. 

    The main components consist of an entry funnel, a revolving door, a color-sensing gender classification complex, and a water recirculation system.

Entry Funnel

    A custom water funnel was designed to guide the pupae from a large hopper into a 1/4" inner diameter (ID) pipe in a single file. The funnel consists of two parts: an acrylic hopper and a 3D printed pipe inlet. 

    The hopper is glued together by five pieces of acrylic plates; it has an opening on the top surface for pupae/larvae loading and a rectangular opening that connects to the pipe inlet. On each of the acrylic plates, slots are made to seamlessly match with the flanges on the complementary piece for the ease of assembly. On the back wall, a clamping space is cut out to hold the water tube in place (in the final product, a bar is added on the corner to hold the tube instead). 

    The pipe inlet is printed on the Connex3 3D printer. The inner dimension shrink from a rectangular shape of 2.5"x0.5" to as small as a 1/4" circle that matches the pipe size. At the tip of the inlet is a push-on pipe fitting made by referencing the Plastic Barbed Tube Fitting on McMaster-Carr. There are four guiding flanges on the outer rim at each surface to fit around the hopper and provide secure attachment. On the very top side, there is also a bumper that stops over-flowed water from reaching the tip and drip over the water tank.

    A water level sensor is attached to the back wall of the funnel. This is another measure to incorporate control into the system--when the water level reached a certain depth, the Arduino recognizes the signal and shuts the pump off with the electrical switch.

Revolving Door

    The revolving door serves multiple purposes in this project: it secures one pupa under the camera for color detection and guides the known-gender pupa into its designated tubing that leads to the separating tank. The revolving door consists of three important parts made with acrylics and 3D printing machines.

The door holder has one inlet and two outlets oriented like a "T" shape, the outlet is placed on each side of the inlet. In the centerpiece, there are four pockets milled into the cylindrical body to fit only one pupa/larva for scanning. They are spaced 90° from one another, so every 90° rotation will expose the entry and the exit in the holder to a new pocket. The door rotates by a water-proof servo motor controlled by an Arduino board. Once the gender is known, the revolving door rotates 90 degrees clockwise to lead the pupa into one separating tank. If the sensor reads the opposite gender, the door will rotate 90 degrees in the opposite direction. A wall cut from standard-sized 2" pipe is attached to support the servo and to prevent water overflow.

    The current holder is 3D printed in Makerbot Method and painted with acrylic paints to prevent leaking. But ideally, it should be printed on the Connex3. The centerpiece is machined with an acrylic block on a CNC machine.

Color Detection

  The vision system serves to classify the male and female pupae based on color. The genetically modified male carrying the fluorescent protein gene glow when excited by fluorescent lights, while the female pupae do not. The USB 2.0 Digital Microscope made by Plugable was chosen for the final design because it can capture and zoom images of the pupae, allowing image processing to filter and classify the pupae using RGB values. The color detection station is set up as followed:

    The digital camera allowed detailed microscopic images to be taken as shown below.  The colored beads are similar in size to the FP pupae and served as test substitutes whenever FP pupae were not made easily available. The images can then be processed and filtered to isolate for selected colors; green beads and blue beads were easily classified using user-determined RGB values.

The picture on the left above shows the camera image without a filter. The beads are about 1mm in diameter, but the camera is able to magnify and focus on the frame. The picture on the right is the filtered image. It picks out only the specified red, green, and blue wavelength and filters the rest, resulting in the appearance of three color beads only. The digital camera is connected to a PC using the standard USB 2.0 connection. The camera settings can be adjusted using the included software from Plugable.