Problems with Current Set-Up:

• Heat dissipation in the length of water tubing

• Inability to focus due to stage thickness

Design Criteria:

1. Maintain target temperature of 37.4 ± 1°C.

2. Feedback and consistency maintained through a sensor-controller system.

3. Maintain current heating area dimensions.

4. Stage will be 0.15 - 0.30 cm thinner.

5. Design and implementation will cost less than $800.00.

Proposed Design:

Figure 1: Proposed design schematic.

Final Design:

The design consists of a flexible silicon rubber fiberglass insulated heater adhered to an anodized aluminum surface. The heater is controlled by a proportion integration differentiation (PID) controller with dual solid state relay outputs. Feedback is provided to the controller from a type-T thermocouple.

Figure 2: Drawing of the Anodized Aluminum and Heater assembly for in vivo usage.

Figure 3: Drawing of the stage for in vivo usage.

Figure 4: Drawing of the Anodized Aluminum, Heater, and Stage assembly for in vivo usage.

Figure 5: Drawing of the Anodized Aluminum plate and two adhered silicone fiberglass rubber flexible heaters for in vitro stage usage.

Figure 6: Schematic all of the wiring necessary for the in vivo set up.

Figure 7: Schematic of the heaters wired together in parallel for the in vitro set up.

Figure 8: Schematic of the wiring necessary for the in vitro set up.

                Figure 9: Picture of the inside of the JCJI2005.

Figure 10: Outer view of the front of the JCJI2005.

Figure 11: Outer view of the back of the JCJI2005.

Calibration/Evaluation Information: 

The calibration/evaluation of the JCJI2005 took place in there steps.  Below is a description of the steps and the results obtained.

This stage involved testing the temperature system by placing the thermocouple sensor into a beaker full of water resting on a warming hot plate.  The system was monitored against a calibrated Listhmus meter.  The temperature of the water was measured several times at different temperatures by both the Listhmus meter and the thermocouple sensor.  A set point adjustment was planned to be made if the propagation of error was ±1.0°C.  If a set point change was necessary, then this stage was repeated.

Table 1: Calibration/Evaluation Stage One Results

As can be seen by Table 1 above, mean difference is well within the ±1°C requested by Dr. Eppihimer. 

Calibration/Evaluation: Stage Two:

The second stage of calibration/evaluation was completed using a rat model.  This was due to the fact that there was a mix up with the delivery of the animal.  However, when the implications of this mix up were discussed with the sponsor, it was determined that a rat would provide an idea as to the absolute longest time necessary to reach body temperature.  This thought was based on the fact that rats are much larger in mass than mice and therefore would take longer to heat up. 

Table 2 Results of Calibration/Evaluation Stage Two Experiment 1.  The table shows the variation in the body temperature of a rat resting on the heater.

 As can be seen by Table 2 above, the rat reached body temperature within 21 minutes.  However, its temperature continued to rise.  Additionally, the group felt the anodized aluminum plate which was in between the heater and the rat and noticed that it was extremely hot.  This prompted the group to use an additional thermocouple and measure the temperature of the plate.  It was measured to be over 70°C.  Obviously, this temperature is very high and could potentially injure the animal.  Due to difficulties, the group consulted Omega.  After talking to a technical representative, the group determined that the percent high value on the controller in the Output 1 menu needed to be decreased.  Additionally, the group determined that a change in the design of experimental set up was necessary in order to ensure that the anodized aluminum plate does not reach such a high temperature and therefore injure the animal.

One of the group members had the idea of taping the thermocouple to the anodized aluminum plate.  This would ensure that the plate never reached a temperature significantly higher than body temperature.  The body temperature of the mouse could be monitored using the instruments already available in the sponsor’s laboratory.  This altered design was proposed to the sponsor, who agreed and allowed the group to continue forth with their work. 

The group completed a second experiment in this calibration/evaluation in order to test the altered design.  A mouse was used post experimentation by the sponsor.  Dr. Eppihimer informed the group that during his experiment he did use any methods to alter the body temperature of the mouse.  A Cole-Palmer temperature sensor available in the sponsor’s laboratory was inserted into the intraperitoneal cavity of the mouse in order to monitor body temperature.  The results of this experiment can be seen below in Table 9. 

   Table 3 Results of Calibration/Evaluation Stage Two Experiment 2.  The table shows the variation in the body temperature of a mouse resting on the heater.

As can be seen by Table 3 above, even after an hour the mouse still did not reach body temperature.  Dr. Eppihimer was present throughout the experiment and predicted that this would be the outcome of the experiment.  He predicted this based on the fact that the mouse’s initial body temperature was so low and thus may not be able to fully return to core body temperature.

Conclusions:

            The group recommends that Dr. Eppihimer continue to use the Cole Palmer temperature sensor in order to monitor the internal body temperature of the mouse.  Additionally, the group recommends that Dr. Eppihimer place the mouse on the anodized aluminum heater assembly as soon as it is anesthetized to ensure that its body temperature does not decrease too much and therefore cannot be brought back to 37.4°C.   Also, as was previously stated, the electrical diagrams for the wiring for the second in vitro output are included in Appendix A if the sponsor chooses to set it up.