SUPPLEMENTAL  MATERIAL   A. COMSOL simulation of the temperature in the incubation chamber We made simulations of the variation of the temperature in the chamber using COMSOL

multiphysics software.  We used the constants indicated in the Table SI. The ends of the wires

are set to 0 ºC. The device is immersed in air whose temperature away from the device is

26ºC.  The temperature, at the bottom of the chamber (300 µm below the copper wires) varies from

11.9 ºC (near the wall) to 13.1 ºC (4.1 mm away from the wall, i.e. in the middle of the

chamber) as shown in Figure S1.

The experimental temperature in the middle of the chamber (14.2 ºC) is in good agreement

with the simulation (13.1 ºC). The simulation also indicates that the temperature in the

chamber is homogeneous, with a variation of 1.2 ºC between the coldest (walls) and the

hottest (center of the chamber) part (Figure S2 (a)).

FIG. S1. Simulation of the variation of the temperature inside the chamber. (a) 3D view of the temperature in the device (only the chamber is simulated). The slice shows the temperature at the bottom of the device. (b) Cross section view of the device. In order to find out the maximal chamber width that can be cooled with this method, we

investigate the maximal and minimal temperature at the bottom of the chamber as a function

of the chamber width, all other parameters being equal (Figure S2 (b)). The maximal

temperature ranges from 10.6 ºC for a 2 mm wide chamber, to 15.7 ºC for a 16 mm wide

5

10

15

20

25 air PDMS Copper wire

Chamber

w1 w2

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chamber. Considering the sol-to-gel temperature of 17 ºC, our cooling system should allow

gelation in chamber of the order of 16 mm.

FIG. S2. Simulation of the variation of the temperature inside the chamber. The temperature is chosen at the bottom of the chamber. (a) Temperatures along a line joining the wall 1 (w1) to the wall 2 (w2) of the chamber (the chamber width is 8.3 mm). (b) Variation of the minimum and the maximum temperature as a function of the chamber width. The minimum temperature is measured at the wall 2 (w2). The maximum temperature measurement is done at the center of the chamber (“C” point). TABLE SI. Values of the constants used in COMSOL Simulation (superscripts refer to the reference

used for the parameter)

Materials

Units

PDMS (1/10)

Glass

Mineral Oil

Density (ρ)

Kg/m3

9201 22352 840 kg.m3  

Thermal conductivity

(k)

W/m.K 0.153 1.132 0.13074

Heat capacity (C)

J/kg.K 15005 7102 16706

B. Control experiments for DNA amplification in agarose The DNA amplification has been performed, for control, in various concentrations of agarose,

in bulk format (i.e. in a 20 μL PCR tube). As shown in the Figure S3, the fluorescence

increases are comparable in all tubes, whatever the concentration of agarose. These

experiments suggest that the agarose gel does not interfere with the reaction.  

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 FIG. S3. DNA amplification reaction in the presence of various concentrations of agarose. The DNA amplification mixtures have been prepared with various concentrations of agarose (from 0. 5% to 2 %). They were then cooled at 4 ºC for a few minutes in order to gelify the agarose. After the cooling stage, all tubes have been incubated in a thermal cycler at 43 ºC for DNA amplification. Whatever the agarose concentration, the fluorescence signal increases as fast as the control, i.e. the DNA amplification occurred in all tubes.    BIBLIOGRAPHY  1. D. Armani, C. Liu and N. Aluru, Twelfth IEEE International Micro Electro

Mechanical System Conference, 222-227 (1999). 2. I. Wong, S. Atsumi, W. C. Huang, T. Y. Wu, T. Hanai, M. L. Lam, P. Tang, J. A.

Yang, J. C. Liao and C. M. Ho, Lab Chip 10 (20), 2710-2719 (2010). 3. O. K. Bates, Ind Eng Chem 41 (9), 1966-1968 (1949). 4. L. H. Huang and L. S. Liu, J Food Eng 95 (1), 179-185 (2009). 5. A. Elliott, J. Schwartz, J. Wang, A. Shetty, J. Hazle and J. R. Stafford, Laser Surg

Med 40 (9), 660-665 (2008). 6. C. Xie and J. P. Hartnett, Int J Heat Mass Tran 35 (3), 641-648 (1992).    

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