the spiral were designed according to the size of tubings. In our

case, we used 2.278 mm diameter inlet and outlet holes. The

inner outlet has a width of 450 μm, and the outer outlet has a

width of 650 μm.

7. There dimensions of the spirals are not limited to the two

designs we described here. Users can customize and test their

own designs easily with this protocol. The two designs we

suggested here were tested in our previous works. Due to the

flexibility of PDMS, the PDMS chip and direct printed chip

with same dimension might not work at the same flow rate,

which need to be calibrated.

8. Fabrication in a cleanroom environment reduces the risk of

having device defects caused by particulates and dust. Printing

quality also directly affect the integrity of device. Make sure the

resin tank of the printer is always free of debris and dust.

9. Only peel off the protective layer on PMMA sheet right before

binding the chip to avoid dust in the channel.

10. Glue resin around the inlet tube and cure it to prevent leakage.

11. The length of outlets tubings need to be the same. Otherwise,

it causes an imbalanced pressure between the two outlets and

consequently affects the focusing position and separation effi-

ciency of the device.

12. Incomplete mixing of PDMS with the curing agent results in

uncured PDMS left on the surface of the mold during casting.

The mold will be hard to clean afterward as well. Therefore,

sufficient PDMS mixing is critical.

13. Resin mold might crack under high temperature, depending

on the type of resin. So it is recommended to cure the PDMS

chips in a low-temperature oven. However, after the first cure

in the 45
C oven, the mold will be able to resist at least 65
C

temperature without cracking (heat treatment).

14. PDMS-made channels fabricated from resin mold are weaker in

plasma bonding compared to micromilling or silicon wafer

mold. Binding PDMS with other materials, such as glasses,

can improve the bonding strength if leakage happens.

15. The inertial focusing of particles takes a few seconds to reach

steady state and get focused in the desired positions in the

channel. During the transition period when pumps start and

stop the particles are randomly dispersed in the channel.

Acknowledgments

M. E. W. would like to acknowledge the support of the Australian

Research

Council

through

Discovery

Project

Grants

Bioreactor-Based Adherent Cells Harvesting from Microcarriers with 3D. . .

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