Final Design

Abstract

After a steady thirteen-week effort, the MAE198: Mouse Drinkomenter team has built an operational experiment system that measures fluid volume consumption and is compatible with fiber-photometry. The objective of the project was to optimize a device that is able to quantify mouse’s real-time liquid consumption and qualify mice behavior with observation of neuron activity. The project was based on the Mouse Lickometer Project from spring 2019. The existing devices were hard to clean and maintain since the parts were epoxied permanently together. In addition, the wireless function sometimes failed, which may have been caused by the float IP address on each microcontroller. Also, the existing fluid system was positioned at the top of the cage, which was not compatible with the fiber photometry system. To solve these problems while maintaining the advantages of the previous project accomplishments, we redesigned the valve system, redesigned the housing structure, created a GUI, and performed analyses on the new system. After this quarter’s optimization project, our device has advantages on easy maintenance, stable data transmission, compatible with fiber photometry system, and measurement precision. 

Executive Summary

The optimized experiment system can be divided into three core components: mechanical, electrical, and software. As for the mechanical part, there are two liquid solutions: one containing water and the other a water-ethanol solution. The liquid system is composed of a differential pressure sensor, a photo interrupter, a drinking valve, flexible tubes, and quick release connectors. For the electrical part, the electronics are connected to a PCB board, which can amplify and filter the signal from a differential pressure sensor, and a microcontroller which transmits the real time data to the computer by cables. Both the mechanical and electrical components have been structurally redesigned to better meet experiment needs, such as compatibility with fiber photometry, maintained reliability, and easily iterable. The software serves as the front-end of the experiment. The researcher would be able to control the cages via a graphic user interface (GUI) and easily retrieve experiment data. It is recommended to install the GUI on a host computer and use a wired connection for up to four experiment cages. Properly setting up this system will allow for successful experiments.

Summary of Performance

• • Measurement Precision

    • Preserve fluid measurement accuracy to 10µl

  • Data Precision

    • Transmit data to computer stably and reliably

  • Easy Operation

    • Control experiment cages via a GUI with minimal physical interaction and user error

  • Robust & Iterable

    • Perform multiple experiment sessions successfully

      • Easy to clean system and replace fluid solutions

Pressure Sensor Calibration

• 1. Current Test Tube

     • Test tube diameter = 8 mm

     • Water Volume and analog count ratio = 0.779 uL/analog count

     • Ethanol volume and analog count ratio = 0.794  uL/analog count

  2. Procedure

     • Extract 10 uL from open glass tube, and record the analog counts output from microcontroller until total amount of  200 uL is extracted.

  3. Results:

     • Water

       1. Slope = 0.74614 ± 3.93%

       2. Theoretical slope = 0.7792

     • Ethanol

• • • 1. Slope = 0.8329 ± 1.32%

      2. Theoretical slope =  0.8047