# Microscope Enclosure for Temperature Regulation and Light Isolation
## 4 Discussion  
Incorporating air distribution baffles improved the temperature uniformity throughout the enclosure. However, there are some design considerations if air baffles are included. First, with side mounted air baffles, warmer air will rise within the enclosure (Figure 2c), which may create temperature gradients in the system. This could result in unexpected instabilities in the optics. To improve the temperature gradient, we biased the incoming supply air towards the bottom of the supply baffle panel (Figure 2d). This scheme is similar to the typical air duct configuration in a cold-climate home, with the supply vents near the floor. After adjusting the baffles, the temperature varied approximately 2 \({}^{\circ}\)C between probes and the time variability of individual probes was approximately 0.2 \({}^{\circ}\)C. This time-dependent variability is dependent on the heater/cooler feedback system. The addition of a local sample temperature regulator may help provide an even more precise sample temperature [10]. We also observed with side airflow baffles that the air on the return side was cooler than on the supply side (Figure 3b). This problem may potentially be reduced by flowing the air from bottom to top vertically through the enclosure, resulting in both sides experiencing similar heated air. However, the frame of the microscope may still shield the sample itself from a vertical air flow, so probe measurements should still be conducted if temperature stability is critical. Vertical air flow could be achieved by incorporating air baffle panels in the floor and ceiling of the enclosure. Specifically, the supply panel could sit just above the table surface, fitting around the microscope base and any optics mounted to the table, and the return air baffle could be incorporated into the roof of the enclosure. Alternatively, it may be possible to use the optics breadboard itself as the bottom baffles. This would require an internally open optics breadboard, and the ability to close all the external mounting holes. However,  
Figure 3: Enclosure temperature with the heater temperature sensor attached directly to the objective of a microscope. (**a**) Thermocouples were placed at 8 locations in an inverted microscope enclosure (same as Figure 1a). Probe 1 was attached, along with the heater feedback probe, directly to metal housing of the objective. All the other probes were in the air. Probes 2 and 6 were on the left side of the microscope (5 cm from the outgoing return air baffle panel), probes 3, 4, and 5 were on the right side of the microscope (10 cm from the incoming supply air baffle panel), and probes 1, 7, and 8 were in the center. Probes 1, 3, 5, 6, and 7 were all at a similar height from the table as the objective (30 cm), while probes 2 and 4 were closer to the table (15 cm), and probe 8 was the farther from the table (60 cm). Probes 1, 2, and 5 were 20 cm from the front of the enclosure, while probes 3, 5, and 6 were about 40 cm, and probes 7 and 8 were 65 cm (near the back). (Note: In this figure, the microscope stage, brightfield illumination optics, and top and front panels are not illustrated.) (**b**) Temperature readings were collected after the setpoint of the heater was changed to 37 \({}^{\circ}\)C. The probes closer to the incoming supply air baffle panel experienced higher temperatures than those shielded by the microscope. In addition, while equilibrating, the air temperature went significantly above 37 \({}^{\circ}\)C.  
if this option is possible, this design would significantly simplify the supply of air from below the microscope, and still allow mounting holes to be used on the breadboard. Our optics breadboards do not have this option, and we need frequent access to the mounting holes; therefore, we decided to utilize the simpler side baffle design. Another consideration is placement of the heater's temperature sensor.