Supplementary information
Investigation and improvement of reversible
microfluidic devices based on glass-PDMS-glass
sandwich configuration
Qiang Chen,1 Gang Li,1,* Yuan Nie,2 Shuhuai Yao,2 and Jianlong Zhao1,
1
State Key Lab of Transducer Technology, Shanghai Institute of Microsystem and Information
Technology, Chinese Academy of Sciences, Shanghai 200050, China.
2
Department of Mechanical Engineering, the Hong Kong University of Science and Technology, Hong
Kong, China
* To whom correspondence should be addressed. Phone:
+86-21-62511070-8703. Fax: +86-21-
62511070-8714. E-mail: gang_li@mail.sim.ac.cn.
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Modeling. The numerical models were created in ANSYS. The models were created to match devices
geometry and used material properties from literature. For the PDMS-glass device, the model includes a
glass substrate and 1.5 mm-thick PDMS slab containing a cavity of 10 mm (L) × 10 mm (W) ×100 μm
(H). Both the PDMS and glass were assumed to behave in a linearly, isotropic form. The glass and
PDMS were meshed with SOLID187 elements. These elements are 3-D, 10 node elements, which have
three degrees of freedom in the x, y, and z directions. The PDMS is allowed to move vertically (z). The
bottom surface of the glass block is constrained in all directions. Pressure is applied in a direction
normal to each surface in the microchamber: The floor, roof, and walls. The model of the glass-PDMSglass device includes two glass plates and a sandwiched 1.5 mm-thick PDMS slab (or 250 μm-thick
PDMS film) containing a cavity of 10 mm (L) × 10 mm (W) ×100 μm (H) between. Again the bottom
surface of the lower glass block is completely constrained and pressure is applied in a direction normal
to each surface in the microchamber. Due to the difficulty in defining the boundary condition for the
reversible PDMS-glass interface, a “glue” boundary was set for all PDMS-glass interfaces, namely,
elements were shared at the interface but they can respond to stimulus as rigid bodies. Although this
simple model cannot directly show the deformation and lamination of PDMS-glass interface, it can be
used to roughly estimate the deformation of PDMS and the stress on the PDMS-glass interface induced
by the deformation of PDMS. Since the tensile stress induced by the deformation of PDMS is directed
up and opposite to the bonding force of PDMS-glass interface, the larger the deformation of PDMS and
the stress on the PDMS-glass interface, the greater the probability of breakage of bonded PDMS-glass
devices.
Fig. S1 shows the solutions to three models at 1 kPa with coloring to indicate displacement. The glassPDMS-glass model shows much less deformation than the standard PDMS on glass model. Fig. S2
compares the max displacement in z-direction of PDMS and the tensile stress on the PDMS-glass
interface induced by the deformation of PDMS under different working pressures for three assembly
configurations. Among three assembly configurations, the PDMS film-based sandwich configuration
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shows the smallest z-direction displacement of PDMS component and the smallest stress on the PDMSglass interface under the same working pressure, so it can withstand the highest working pressure.
Fig. S1 Results of structural simulations of the PDMS deformation under a 1 kPa hydrodynamic
pressure. (a) The model for the PDMS-glass construction; (b) The model for the PDMS slab-based
sandwich construction; (c) The model for the PDMS film-based sandwich construction.
Fig. S2 The simulated plots for (a) the max displacement in z-direction of PDMS component and (b) the
max stress on the PDMS-glass interface in PDMS-based devices, respectively, vs the working pressure.
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