37
(a) e side-wall electrode
and microchannel
(c) Assembly
(b) e bottom electrode
and trap pillar
Drilling Holes
Plasma
Wiring
V-Shape Pillar
SU-8
Glass
C-PDMS
PDMS
ITO Glass
BN303-30
Figure 2.18: Chip fabrication: (a) thick electrode and microchannel fabrication: (i) A 160-µm thick
SU-8 photoresist (SU-8 2075) is spin coated on a glass substrate. e photoresist is patterned using
a photolithography process to form a SU-8 mold; (ii) press the C-PDMS onto the SU-8 mold and
then slowly scrape o the excess C-PDMS with a blade. en, it is baked at 80° C for 30 min for
curing; (iii) pour the PDMS onto the cured C-PDMS mold and remove bubbles. en, it is cured at
80° C for 30 min; (iv) the PDMS and C-PDMS are removed from the SU-8 mold; and (v) punching
holes on PDMS/C-PDMS; (b) fabricate bottom electrode and V-shape structure: (i) spin coating and
pattern 1–2-µm thick negative photoresist (BN303-30) on the ITO glass substrate; (ii) etching the
ITO substrate to form bottom electrode; (iii) spin coating SU-8 photoresist of about 25-µm thickness
on the ITO glass and fabricating a V-shape structure; and (c) chip assembly: (i) the upper layer and
the bottom layer are treated by plasma-oxygen (power 30 W, time 60 s), and are aligned and bonded
together; (ii) blocking of the microchannel. Since C-PDMS electrodes are independent of each other,
the formed microchannel can’t be completely closed, thus port sealing is required. To do so, a small
amount of PDMS is injected into the four inlets, and baked at 80° C for 30 min for curing; and (iii)
external wiring of the chip, the ITO electrode leads the C-PDMS electrode through the wire, and the
inlet and outlet of the microchannel are led out through pipe.
Figure 2.19 shows a photo of the microchip.
Figure 2.19: e photo of the 3D rotation microchip.
2.4 CHIP FABRICATION