This journal is © The Royal Society of Chemistry 2004
Power-free poly(dimethylsiloxane) microfluidic devices
for gold nanoparticle-based DNA analysis
Kazuo Hosokawa1, Kae Sato1, Naoki Ichikawa2, and Mizuo Maeda1
1Bioengineering
2Institute
Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198 Japan
of Mechanical Systems Engineering, AIST, 1-2-1 Namiki, Tsukuba, Ibaraki, 305-8564
Japan
Electronic Supplementary Information
Table of contents
A sample movie used for the flow characterization
(In a separate file)
Mathematical details of the one-dimensional diffusion model
Page S-2
Time course of the gold nanoparticle deposition
Page S-3
S-1
This journal is © The Royal Society of Chemistry 2004
Mathematical details of the one-dimensional diffusion model
Fick’s second law of diffusion:
C
 2C
D 2 .
t
x
(S1)
The boundary conditions:
C ( x, 0)  C0 ,  l  x  l ,
C ( l , t )  C (l , t )  C1 , t  0.
(S2)
The solution:25

C  C1  2C1  C0 
( 1) n
n
n 0
cos n
x
2n  1

2 D 
exp   n 2 t , n 
.
l
l 
2

(S3)
Surface air flux:
C
FD
x
x l
2 DC1  C0  

2 D 

exp   n 2 t  .

l
l 

n 0
(S4)
Taking the first term of Eq. (S4), we obtain Eq. (1) in the main text. Error is less than 1 % when
D t / l2 > 0.24, which corresponds to t > 4.7 min in our system.
The total mass index:
 C  C dx  2 1
m

 C  C dx
l
1
l
l
l
0
1

n 0
2
n

2 D 
exp   n 2 t  .
l 

(S5)
Taking the first term of Eq. (S5), we obtain Eq. (2) in the main text. Error is less than 1 % when
D t / l2 > 0.14, which corresponds to t > 2.7 min in our system.
S-2
This journal is © The Royal Society of Chemistry 2004
Time course of the gold nanoparticle deposition
To evaluate the kinetics of the deposition process, we tracked temporal change of the intensity of
the black line (Fig. 6 in the main text) from a video image.
Methods
Methods were basically the same as described in the main text. However, we used
the Hamamatsu video camera instead of the Olympus still camera in this case. The video image was
recorded in a personal computer equipped with a video-capturing interface (Library, Himawari
PCI/S; Tokyo, Japan), and was analyzed using free image-processing software (ImageJ,
http://rsb.info.nih.gov/ij/).
Results
As described in the main text, a black line appeared at the interface between the
streams of Au-P and T1. We chose a 20 pixel square (11 m square) sampling area in the black line,
and measured the mean intensity of this area every 1 s. On the other hand, we could not find any
deposition for T2. Therefore we determined a sampling area for T2 at the symmetrical position to
that for T1. Signal from the second sampling area is substantially a background noise. As shown in
Fig. S1, the intensity of the black line sigmoidally changed with the course of time, and was almost
saturated after 10 min.
Figure S1. Time course of the intensity of the deposition image. Intensity range is 0 to 255 (255
means black). Origin of time is defined as the establishment of flow.
S-3