surface of an appropriate substrate with the support of special polymers which are

sensitive only to the well-defined wavelengths of light which would finally create

desired geometric patterns on a substrate. These microfluidic systems are employed

(Ma et al. 2017) to create lab-on-a-chip devices which are illustrated in Figs. 16.26

and 16.27. The next section deals with a specific application known as heart-on-a-

chip which would help and go a long way to find solutions for CAD.

16.7.1 Heart-on-a-Chip

The standard static cell culture approach lacks in fully capturing the intricate in vivo

environment. In addition, the current drug discovery process is currently a very

difficult and costly process. Moreover, majority of the drug candidates fail to enter

even clinical trials. In such a scenario, microfluidics play a vital role in biological

research domains which include diagnostic sector, disease modeling, and therapeutic

approaches. These include cardiac research area also. Microfluidic technology along

with stem cell technology has been playing a revolutionary role in the cardiac tissue

engineering which has resulted in fabrication of cardiac lab-on-a-chip which is also

known as heart-on-a-chip device (Kitsara et al. 2019). It has been made possible to

recreate cardiac tissues using cell culturing techniques in a highly spatiotemporally

controlled microenvironment (Chan et al. 2015) from patient-specific models to

mimic the natural habitat of the heart cells. This has resulted in heart-on-a-chip

devices consisting of numerous imprinted microchambers as well as microchannels

on a polymer which is bonded on another material (normally a glass). Transparency

and biocompatibility (which is defined as the extent of its permeability to oxygen

and carbon dioxide) (Crone 1963) are two required properties of the polymeric

material to be used for this application. Such characteristic properties are easily

met by the material polydimethylsiloxane (PDMS).

Cells are housed in microchannels and microchambers to which reagents like

growth factors, cytokines, and nutrients are delivered. ECM-derived hydrogels

(biological reagents) and enzyme/protein stick the cells to the surface and monitor

the dynamics of cell culture. Microchambers are usually lined with primary heart

cells and controlled with the help of microchannels, microvalves, and actuators.

Monitoring is done with the help of digital and biological sensors in addition to the

imaging devices (Zhang et al. 2020; Lammertsma 2002).

Flow in the main and side microchannels usually control transportation of

nutrition (Renkin 1959) as well as waste discharge. Real-time monitoring of the

cells in these microfluidic devices can be carried out by engaging pressure and flow

sensors. Electrophysiology and mechanobiology of the experiment could be con-

trolled by tailoring the chip (Liu et al. 2020) by adding electrical and mechanical

components. This could also help in mimicking the in vivo conditions. These are

known as electrical and mechanical actuators. This can help in actually placing

different electrodes in the chip for stimulating the cell as well as using it as a readout

system. This device is very helpful in probing the cellular behavior against a number

of stimuli.

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Role of Microfluidics and Nanofluidics in Managing CAD

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