Final Design

Design of the Two Chambers

    The only modification that had to be done on the home chamber was machining a rectangle out of one of the walls. This cut was done in order for an adaptor piece to be able to slide in and out of the cage. The purpose of the adaptor is to account for the slight angle in the home chamber and allow for the PVC tube to slide in and out of two vertical walls.The adaptor piece will be on the home chamber most of the time, but it is easy to slide out when the home chambers need to be cleaned. We have also created a door that can slide into the adapter when the two chambers are not attached and the rat will not be able to escape. In order for the PVC tube to easily slide in and out, there are 4 slots that are machined out of the PVC tube in order to be able to fit into each acrylic adaptor piece that is mounted on each chamber. This allows for easy installation for the lab technician, but prevents the tube from being pulled out in the horizontal direction.

    The design for the behavioral chamber was adapted from the full sized behavioral chamber that NEATLabs is using for their testing. This is a behavioral chamber that was designed by the UCSD Prototyping Lab on campus. There are small modifications that were made to this original design in order to meet the requirements for this project. For example, the height of the chamber was decreased to match the height of the home chamber, the door was replaced with a wall that has a hole the size of the PVC cut out, and the top has been replaced with a lid that can be removed. We have also added a case that holds our Arduino and PCB that control the Home Cage Water Delivery System that we have added as will as the motor. Another addition is a water reservoir holder where a large water bottle can be placed and can hold the water not only for the Home Cage Water Delivery System, but also the water for the 5 nose ports.

Water Delivery System Design

    The water delivery system consists of a button activated Arduino system that is able to accurately deliver 15mL of water to the home cage for the rats to have once a day. This design is easy to use and eliminates the frustration that the lab technicians currently experience with having to measure out 15mL a day and then having to account for the error caused by the water bottles. This system is powered by a stepper motor that powers a peristaltic pump in order to deliver water from the water reservoir into a 15mL tube that connects to a drinking valve. The water delivery system is implemented into the home chamber by using the same metal holder that NEATLabs currently uses to hold their home cage water bottles. Instead of using their normal water bottles, we instead decided to store the 15mL in a tube that fits into the holder. The water will be delivered from the water reservoir, through the pump, and into the 15mL tube which is connected to a drinking valve. We decided to use this drinking valve instead of the usual lixit that is attached to their water bottles because it does not leak, whereas the lixit leaked. With this drinking valve, the water is stored in the tube until the rat licks the valve. This design allows multiple hoses to go into one water reservoir and deliver water to multiple motors. This way one water reservoir will have the water for the home chamber and all the nose ports in one place. 

    This makes it even easier on the lab technicians because they only have to fill up one water reservoir instead of two, as they do now. Currently, the lab technicians have expressed frustration with having to fill up precisely 15mL of water into each home cage and having to account for any water left over after the rats finishing drinking it. Filling up the water bottles can take up to half an hour to fill up about 15 water bottles. With the our automated Water Delivery System, the technicians will only need to press one button on each cage, which will take about a minute or less to do for all the cages. This saves lab technicians both time and frustration. The implementation of the water delivery system can be seen below. 

Implemented Water Delivery System

Prototype Performance

In order to be able to accurately deliver 15mL of water from our water delivery system, there was testing done in order to see how accurate of a delivery we could get. From the data table below, it is shown that in order to get 15mL of water, 547,500 steps are needed to be programmed to the motor. From the graph below, it can also be seen that a best fit line was created from our data points to be 2.75E-05*X - 0.0433. Using this best fit line, we can use it to adjust the step count in order to be able to deliver different amounts of water if need be. 

Setup for Water Delivery System Testing

This graph shows the linear relationship between the number of steps the motor runs and the volume of water that it delivers. 

    Although we were not able to get the last electronics in order to have a working behavioral chamber, we were able to take our chamber over to our sponsors and have a rat roam around to test the animal interaction. For this experiment, we observed Rat 118’s behavior moving around the system for 10 minutes. One thing to note about Rat 118 is that this rat had never been exposed to any type of human interaction or training yet. Our sponsor decided to use a rat with no experience in order to get the worst case scenario of animal interaction. The other rats in the lab are already used to human interaction and being pre-trained and/or tested on. Also, a rat with no prior training experience is the typical type of rat that will be using our chamber. Rat 118 was very curious as soon as he was placed into the home chamber. He instantly walked through the bridge and continued to move back and forth between chambers at a rate of 5 times/min. Pictures of Rat 118 exploring our chamber can be seen below.

Rat 118 exploring the chamber

Rat 118 walking through the bridge

Rat 118 looking through the gap between the bridge and the adapter