Fruit Fly Wind Tunnel with Panoramic VR Display

FINAL PROTOTYPE SOLIDWORKS MODEL

Background

Selection experiments are among mankind’s oldest activities, giving rise to the domestication of animals and plants for maximum benefit in their utilization. Selection capitalizes on the genetic variation of a species through propagation of the specific organisms of a generation that express desired traits. Through many generations of selection, a population may have a new homogenous characteristic e.g. sweeter bananas, cows with more milk, pigs providing more bacon, etcetera.

The Greenspan Laboratory performs experiments pertaining to neurobiology and genetics through testing of Drosophila, or the fruit fly. The lab is currently funded by the United States Army (through DARPA) for the study of genetic expression involving physical fitness. While knowledge of human gene expression of fitness is more applicable, its acquisition is difficult and time consuming. Therefore propagation of fitness genes through generations of the short-lived fruit fly was the chosen medium of study. The fruit fly genome shares over 60% of its DNA with the human genome, making the study of drosophila highly robust and practical.

Objective

The team's objective is to construct the apparatus to be used in the selection of fruit flies.

The apparatus will be a wind tunnel per request of our sponsors.

Functional Requirements

The apparatus must:

• • 1. Allow for differentiation of fruit flies based on physical fitness by testing in a wind tunnel

    • a. Flow speeds must be adjustable and able to reach 0.6 m/s

    • 2. Position locking of flies into compartments to allow subsequent asphyxiation using carbon dioxide

    • a. Dividers must allow airflow but stop flies from passing through

    • 3. Motivation of flies to move forward against wind using projection of visual stimuli on walls (optomotor response)

    • a. Projections must refresh at greater than 200 Hz for continuous image recognition in flies

Introduction to the Design

The final design is a sealed acrylic wind tunnel. Flies are contained once they are inputted through the swivel cap at the downwind end. Airflow is generated by four axial fans at the upwind end with a honeycomb filter to laminarize flow. The walls of the tunnel have been coated to allow projection onto them by a projector-mirror system. The projected images stimulate flies to move forward against the wind during a trial. At the end of a trial, the mesh compartment dividers (or sliding doors) are dropped into the tunnel, separating the flies into three compartments. The flies in the tunnel can then be temporarily paralyzed by blowing carbon dioxide into the fans. Flies may then be selected and removed based on desired characteristics.

Performance

• The stimulus projections onto the walls successfully motivated flies within the tunnel to move forward

• Wind speeds in the tunnel reached 0.57 m/s (short of 0.6 m/s)

  • However, speeds were sufficient for the requirements of the apparatus

  • Flies were overwhelmed by wind at even 70% fan power

• Sliding compartment dividers successfully sealed tunnel into three separate spaces

  • More dividers may easily be added for greater phenotype selectivity

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