high-density integration with a highly multiplexed microdevice. The microchannels
were separated by a 10μm-thick PDMS membrane containing an array of through-
holes with an active diameter of 10μm. The human alveolar epithelial cells and
microvascular endothelial cells are attached opposite to surface of the 3-D extra-
cellular matrix coated membrane (Fig.8.4D). The device recreates physiological
breathing movements by applying vacuum to the side chambers and causing
mechanical stretching of the PDMS membrane forming the alveolar-capillary
barrier. Epithelial and endothelial cells are grown on either side of a porous thin
Fig. 8.4 (A) and (B) Fabrication and operation of a multi-layer microfluidic device (MMD) for
kidney on chip application (i) fabrication steps (ii) image oftop viewof device (iii) schematic
showinglateral viewof device (iv) SEM image of the cultured cells. Kidney on chip application (i)
fabrication steps (ii) image oftop viewof device (iii) schematic showinglateral viewof device (iv)
SEM image of the cultured cells. [ 29 ]. (C) Microfluidic “alveoli-on-a-chip”. (i) assembly of the
components (ii)horizontaltubules show direction of culture media F-12 K (iii) liquid–air interface
formation at the alveolar surface (iv) A cross-sectional view of the microfluidic device shows the
horizontalorientation for cell culture and the vertical configuration for experimentation [ 30 ]. (D)
Lung on chip device. (i) schematic of fabrication of device. Three PDMS layers are aligned and
irreversibly bonded to form two sets of three parallel microchannels (ii) After permanent bonding,
PDMS etchant is flowed through the side channels. Selective etching of the membrane layers in
these channels produces two large side chambers to which vacuum is applied to cause mechanical
stretching. (E) Images of an actual lung on-a-chip microfluidic device viewed from above [ 31 ]
8 Biological Applications of Microfluidics System 201