# Water Jacket Systems for Temperature Control of Petri Dish Cell Culture Chambers
## 3 Results and Discussion
### Analyzing the Effect of Water Jacket Geometry  
Furthermore, we investigate the effect of the water jacket geometry on the thermal performance of the system, as discussed here.  
Square water jacket:Figure 5a shows the temperature contours of the system using a square water jacket. The temperature contours are similar to those of the reference circular water jacket presented in Figure 2b. However, the extended external surfaces of a square water jacket increased the convective loss across those surfaces. The inlet water temperature was increased from 39 \({}^{\circ}\)C with the circular water jacket to 39.1 \({}^{\circ}\)C to compensate for those extra losses. The flow streamlines presented in Figure S10  
Figure 4: Numerical characterization of the temperature profile along the bottom surface of the Petri dish with respect to Petri dish parameters, including **(a)** Petri dish diameter (\(D_{Petri dish}\)), varying from 15 to 45 mm. **(b)** Volume of biological sample stored inside the Petri dish (\(V_{sample}\)), varying from 25% to 100%. **(c)** Material of the Petri dish, for the cases of polystyrene, polystyrene-glass (with glass only implemented close to the central region of the Petri dish bottom surface) and glass. **(d)** Incorporation of a heater underneath the Petri dish releasing 187 mW. The detailed temperature contours across the middle cross-section of the Petri dish obtained at the above conditions are presented in Figures S6–S9.  
were similar to those of the reference circular water jacket presented in Figure 2a. A total pressure drop of 4.5 Pa was observed between the inlet/outlet ports of the square jacket, which was similar to that obtained for the circular water jacket.  
_Semi-circular water jacket:_ Figure 5b presents the temperature contours obtained for the semi-circular water jacket. Compared to the reference circular water jacket presented in Figure 2b, the semi-circular jacket produced an asymmetric temperature profile with a larger temperature gradient along the radial axis of the Petri dish. Despite a large temperature gradient, no buoyancy-driven flows  
Figure 5: Numerical simulations indicating the change of temperature distribution across the Petri dish by varying the geometry of the water jacket. (**a**) A square water jacket led to symmetrical temperature contours similar to those of a circular water jacket. (**b**) A semi-circular water jacket led to asymmetrical temperature contours due to formation of cold and hot regions across the Petri dish. (**c**) Comparison of temperature profiles along the radial axis of circular (reference), square and semi-circular water jackets revealing temperature gradients of 3.28, 3.29, and 12 \({}^{\circ}\)C, respectively. The flow streamlines associated with the square and semi-circular water jackets are presented in Figures S10–S11.  
were observed inside the Petri dish. The flow streamlines presented in Figure S11 are similar to those of the reference circular water jacket presented in Figure 2a.  
Figure 5c compares the temperature profiles along the radial axis of Petri dish at \(z=1\) mm obtained with circular and square water jackets. Both jackets produced symmetrical temperature profiles with almost similar temperature gradients of 3.28 and 3.29 \({}^{\circ}\)C obtained across the Petri dish, respectively. In contrast, the semi-circular water jacket produced an asymmetrical temperature profile with an impressive temperature gradient of 12 \({}^{\circ}\)C. Such a large temperature gradient might be of particular interest for researchers studying the sensitivity of cells to medium temperature, as presented in Figure 5b.