**1. Introduction: why cell and organ on chip?**

The field of microfluidics or lab‐on‐chip (LOC) technology aims to advance and broaden the possibilities of bioassays, cell biology and biomedical research based on the idea of miniaturi‐

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zation. Microfluidic systems allow more accurate modeling of physiological situations for both fundamental research and drug development [1].

Drug discovery and research is the prime aspect of any pharmaceutical company. The past 50– 60 years have witnessed significant scientific and technological growth in entire field of biotechnology, computational drug design and screening and advances in scientific knowl‐ edge, such as an understanding of disease mechanisms, new drug targets and biomarkers discovery. In principal, these advancements should also be reflected in rise of new commercial products and drugs, but unfortunately, the pharmaceutical industry is facing unprecedented challenges owing to rising costs and the declining efficiency of drug research and development. Modern drug development requires implementation of extensive preclinical testing, and validation protocols before potential therapeutic compounds are approved to progress to clinical evaluation. This process is costly and time‐consuming, as well as inefficient as for every 10 drugs entering clinical trials, only one or two will typically be licensed for eventual use in humans [2]. The number of new drugs approved per billion US dollars spent on R&D has halved roughly every 9 years since 1950, falling around 80‐fold in inflation‐adjusted terms.

The failures of drug clinical trial are primarily due to the poor predictive power of existing preclinical models. The existing cell culture techniques often failed to mimic the complexity of living systems and are incapable of modeling situations where organ‐organ or tissue‐tissue communication are important. Moreover, cells maintained in standard *in vitro* culture conditions often suffer from incomplete maturation or are held in a configuration that prevents their full functional development, making predictions of *in vivo* tissue function more difficult to extrapolate. Although animal models preserve the intricacy of living systems, due to the inherent complexity of interconnected tissues, elucidation of specific mode of drug action is often difficult that leads to confound observations. Furthermore, animal models have, on multiple occasions, been predicated human responses to drug treatment in a rather harmful way [3, 4]. The drug discovery community has identified the critical need for new testing approaches and an intermediate human *in vitro* model in the early stage of drug development to generate reliable predictions of drug efficacy and safety in humans that could mitigate the side effects observed in clinical trials and LOC systems can play a pivotal role in this by fulfilling this unmet need by microengineered cell culture models with miniaturized and automated assays that will increase resolution and precision. These models leverage cutting‐ edge microfabrication and microfluidics technologies to control the cellular microenvironment with high spatiotemporal precision and to present a variety of extracellular cues to cultured cells in a physiologically relevant context [5–6].

This chapter deals with the cutting‐age research in the field of microfabrication technologies and multiorgan microdevices that mimic key aspects of human metabolism. We discuss about latest advancements and how this emerging field transforms the face of biomedicine.

#### **1.1. Need of microfluidics technologies for global health: applications and limitations**

Diagnostic applications for global health have seen a fast pace in recent years. LOC, micro total analysis systems (μ‐TAS) or microfluidics systems are the major breakthrough in this regard and with their state‐of‐art technology, these miniaturized integrated devices have great potential to change the face of healthcare sector globally. Basically, from industrial perspective to develop a high‐throughput diagnosis system, it must utilize small chemical volumes to keep the cost of development at an affordable level. The current trend of miniaturized and auto‐ mated assays can address these issues directly owing to their better resolution and accuracy. Microfluidics devices are new and promising players in healthcare segments. These devices, which scaled down analytical processes in conjugation with advances in microfluidics technology, are the soul motivation behind various chip‐based methods of lower cost and rapid analysis than the conventional laboratory bench‐scale methods. Although these microelectro‐ mechanical systems (MEMS) or miniaturized chip‐based systems have seen a fast pace in other fields, such as electronics, aerospace and computer science, since their inception in early 1990s and have witnessed many innovations based on these techniques, in this chapter, our prime focus is how these technological advancements have been transformed into the face of biomedical sciences with its wide range of biological applications, such as high‐throughput drug screening, single cell or molecule analysis and manipulation, drug delivery and advanced therapeutics, biosensing and point‐of‐care diagnostics, among others. [7]

zation. Microfluidic systems allow more accurate modeling of physiological situations for both

Drug discovery and research is the prime aspect of any pharmaceutical company. The past 50– 60 years have witnessed significant scientific and technological growth in entire field of biotechnology, computational drug design and screening and advances in scientific knowl‐ edge, such as an understanding of disease mechanisms, new drug targets and biomarkers discovery. In principal, these advancements should also be reflected in rise of new commercial products and drugs, but unfortunately, the pharmaceutical industry is facing unprecedented challenges owing to rising costs and the declining efficiency of drug research and development. Modern drug development requires implementation of extensive preclinical testing, and validation protocols before potential therapeutic compounds are approved to progress to clinical evaluation. This process is costly and time‐consuming, as well as inefficient as for every 10 drugs entering clinical trials, only one or two will typically be licensed for eventual use in humans [2]. The number of new drugs approved per billion US dollars spent on R&D has halved roughly every 9 years since 1950, falling around 80‐fold in inflation‐adjusted terms. The failures of drug clinical trial are primarily due to the poor predictive power of existing preclinical models. The existing cell culture techniques often failed to mimic the complexity of living systems and are incapable of modeling situations where organ‐organ or tissue‐tissue communication are important. Moreover, cells maintained in standard *in vitro* culture conditions often suffer from incomplete maturation or are held in a configuration that prevents their full functional development, making predictions of *in vivo* tissue function more difficult to extrapolate. Although animal models preserve the intricacy of living systems, due to the inherent complexity of interconnected tissues, elucidation of specific mode of drug action is often difficult that leads to confound observations. Furthermore, animal models have, on multiple occasions, been predicated human responses to drug treatment in a rather harmful way [3, 4]. The drug discovery community has identified the critical need for new testing approaches and an intermediate human *in vitro* model in the early stage of drug development to generate reliable predictions of drug efficacy and safety in humans that could mitigate the side effects observed in clinical trials and LOC systems can play a pivotal role in this by fulfilling this unmet need by microengineered cell culture models with miniaturized and automated assays that will increase resolution and precision. These models leverage cutting‐ edge microfabrication and microfluidics technologies to control the cellular microenvironment with high spatiotemporal precision and to present a variety of extracellular cues to cultured

This chapter deals with the cutting‐age research in the field of microfabrication technologies and multiorgan microdevices that mimic key aspects of human metabolism. We discuss about

latest advancements and how this emerging field transforms the face of biomedicine.

**1.1. Need of microfluidics technologies for global health: applications and limitations**

Diagnostic applications for global health have seen a fast pace in recent years. LOC, micro total analysis systems (μ‐TAS) or microfluidics systems are the major breakthrough in this regard

fundamental research and drug development [1].

78 Lab-on-a-Chip Fabrication and Application

cells in a physiologically relevant context [5–6].

Extracting new phenomena and elaborated information about the biologically active systems is the basis of all innovations in the field of biomedical sciences. The complex live systems and richness of biological processes are stimulating factors for new LOC approaches, and these emerging technologies are gradually changing the scenario, and now, we can seek experi‐ mental answers at the molecular level.

#### *1.1.1. Development of microfluidics technologies for different applications in healthcare segment*

In a broader sense, microfluidics can be linked to the development of integrated circuit technology and wafer fabrication facilities. They have unique ability to combine different systems possessing high‐throughput capabilities, new data processing and storage strategies. These miniaturized devices provide new tools for highly parallel, multiplexed assays with better isolation, purification and handling of entities, cells or organisms for a simplified, parallel analysis. Initially, silicon and related materials were the preferred choices to fabricate miniaturized devices but now polymeric materials are also the stake holders for because of ease of manufacturing by embossing or molding [8]. They are attached to other surfaces such as silicon, and the formation of fluid channels and patterns on polymeric devices are relatively easy. Other materials, such as semiconductors and metals, are other necessary components of electrical detection schemes, and earlier reports are there where semiconductor nanowires and carbon nanotubes are being studied as sensor components [9, 10]. Integration of mechanical devices with fluid systems for biological implementation and to fabricate disposable systems has been reported earlier and summarized in many reviews [7, 11, 12]. **Figure 1** shows an on‐ chip disposable diagnostic card. In this segment, few latest applications of LOC devices are discussed briefly [50].

**Figure 1.** Example of an integrated disposable diagnostic card. (a) Image of a card. The red O‐rings are for interfacing with off‐card components, valves and pumps, that will eventually be incorporated onto the card itself. (b) Schematic of the card [49].

#### *1.1.1.1. On‐chip DNA hybridization and PCR*

An on‐chip deoxyribonucleic acid (DNA) hybridization assay refers to the bioassay conducted on the microfluidic system/device based on the nucleic acid hybridization technique [13]. From its earlier applications in 1980s, it has been evolved as a powerful tool to detect and identify the presence of a specific DNA sequence. On‐chip DNA hybridization systems are amalga‐ mation of advantages of both microfluidics and hybridization.

In the past 20 years, microfluidics devices have been emerged as an important area of research. As a combination, miniaturization eliminates the need of large reagent consumption, time‐ consuming labor‐intensive procedures and involvement of bulky or expensive equipment while keeping its distinctive advantages of high sensitivity, selectivity and specificity of conventional techniques. Additionally, these miniaturized devices can play a pivotal role in healthcare sector of the Third World countries, by bringing cheaper and smaller, but still sophisticated analytical tools to rural areas and resource‐poor regions [14]. This section focuses on few recent application of on‐chip polymerase chain reaction (PCR) devices. There are few criteria to be taken care of while designing on‐chip PCR systems such as high‐temperature resolution and acquisition rate for precise thermal cycling in microfluidics. Apart from traditionally embedded thermocouples and thermometers [15–17], Wu et al. [18] reported an integrated PCR system with a temperature controller using platinum (Pt) thin film as heater and temperature sensor, an optical detection system and an interchangeable (disposable or modular) PCR chip, which was independent from the two functional systems as shown in **Figure 2**. In this system, Pt thin‐film sensor was patterned to microsize and integrated to thin‐ film heater into the chip to provide rapid response and precise integration.

**Figure 1.** Example of an integrated disposable diagnostic card. (a) Image of a card. The red O‐rings are for interfacing with off‐card components, valves and pumps, that will eventually be incorporated onto the card itself. (b) Schematic of

An on‐chip deoxyribonucleic acid (DNA) hybridization assay refers to the bioassay conducted on the microfluidic system/device based on the nucleic acid hybridization technique [13]. From its earlier applications in 1980s, it has been evolved as a powerful tool to detect and identify the presence of a specific DNA sequence. On‐chip DNA hybridization systems are amalga‐

In the past 20 years, microfluidics devices have been emerged as an important area of research. As a combination, miniaturization eliminates the need of large reagent consumption, time‐ consuming labor‐intensive procedures and involvement of bulky or expensive equipment while keeping its distinctive advantages of high sensitivity, selectivity and specificity of conventional techniques. Additionally, these miniaturized devices can play a pivotal role in healthcare sector of the Third World countries, by bringing cheaper and smaller, but still sophisticated analytical tools to rural areas and resource‐poor regions [14]. This section focuses on few recent application of on‐chip polymerase chain reaction (PCR) devices. There are few criteria to be taken care of while designing on‐chip PCR systems such as high‐temperature resolution and acquisition rate for precise thermal cycling in microfluidics. Apart from traditionally embedded thermocouples and thermometers [15–17], Wu et al. [18] reported an integrated PCR system with a temperature controller using platinum (Pt) thin film as heater and temperature sensor, an optical detection system and an interchangeable (disposable or modular) PCR chip, which was independent from the two functional systems as shown in **Figure 2**. In this system, Pt thin‐film sensor was patterned to microsize and integrated to thin‐

the card [49].

*1.1.1.1. On‐chip DNA hybridization and PCR*

80 Lab-on-a-Chip Fabrication and Application

mation of advantages of both microfluidics and hybridization.

film heater into the chip to provide rapid response and precise integration.

**Figure 2.** Interchangeable PCR chip and temperature control device. (a) Top view of PCR chip. (b) Back side view of heater chip, Pt heater and thermal sensor were integrated in one chip. (c) optical detection system in upper panel [18].

In another approach, Chia et al. developed fully integrated, portable PCR device that consists of the following four major parts: a disposable chamber chip with microchannels and pumping membranes, a heater chip with microheaters and temperature sensors, a linear array of electromagnetic actuators and a control/sensing circuit. Apart from the small size (67 × 67 × 25 mm3 ) and less power consumption (5V DC) and reduced volume of DNA solution, this system could effectively reduce the PCR process time into one‐third of the time required by typical commercial PCR system [19]. In another approach, Steinbach et al. [20] came forward with their K‐Ras mutation detection on chip. **Figure 3** shows schematic of the on‐chip detection device. They aimed to develop a fast and reliable chip‐based K‐Ras mutation based on existing microfluidic chip platform for visual signal readout of K‐Ras mutation profiling. Successful hybrid formation was monitored by streptavidin horseradish peroxidase binding, followed by an enzymatic silver deposition. Silver spots represented robust endpoint signals that enabled visual detection and grey value analysis. This study has the potential to replace expensive detection devices. These few examples give a gist of microfluidics in DNA detection and PCR. Many reviews are available on this topic [13, 21, 22].

**Figure 3.** Assay design (a) The schematic workflow of the assay is pictured, starting from isolation of genomic DNA from cells, DNA amplification and on‐chip hybridization, respectively. (b) The location of KRAS codon 12 mutations within the amplicon and the corresponding capture probes is illustrated (ctr = positive control; wt = wild type; SNP = single‐nucleotide polymorphism; SA‐HRP = streptavidin horseradish peroxidase) [20].

#### *1.1.1.2. On‐chip biosensing and disposable point‐of‐care devices*

Over the past decade, on‐chip diagnostic systems observed explosive growth and showed significant potential for clinical diagnostics specifically for diseases, including toxicity. The early, rapid and sensitive detection of the disease state is the prime objective for every on‐chip clinical diagnosis. Initially, this field was focused on developing the concepts of LOC and later evolved to applications in a number of biochemical analysis operations, such as clinical analysis (blood gas analysis, glucose/lactate analysis, etc.) [23].

In on‐chip diagnosis devices, apart from pregnancy detection kit and glucometer, most applications are based on genes and peptides detection for early indicators of disease [24–26]. For instance, Dinh et al describe a multifunctional biochip with nucleic acid and antibody probe receptors specific to the gene fragments of *Bacillus anthracis* and *Escherichia coli*, respectively [25]. These devices were based on the detection of specific diseases or biological warfare agents by incorporating biomarkers specific to such agents. Monitoring of regular metabolic param‐ eters, such as glucose and lactate, was demonstrated by the I‐Stat analyzer that provides point‐ of‐care testing for monitoring a variety of clinically relevant parameters [26]. Immunosensing applications as a part of clinical diagnostics have also been demonstrated [27, 28].

Recent years have witnessed a vast range of applications of LOC due to the significant benefits of small sample and reagent volume utilization, economic and rapid analysis with less wastage and possibility of developing disposable devices. Ahn et al. demonstrated a fully integrated module of wristwatch-sized analyzer that included a smart passive microfluidic manipulation system based on the structurally programmable microfluidic system (sPROMs) technology, for preprogrammed sets of microfluidic sequencing with an on‐chip pressure source for fluid driving, sequencing and biochemical sensors [23]. Point‐of‐care testing (POCT) is one of the most impressive developments of microfluidics in life sciences and can be defined as diagnostic testing at or near the site of patient care to make the test convenient and immediate. In many countries, DNA test kits for HIV are already available [29]. This is a rapidly growing field, and more detailed information can be obtained from various reviews in this area [23, 31, 32].

**Figure 4.** (a) View of microfluidic chip featuring the two distinct hydrodynamic flow‐focusing regions and expanding nozzle geometry with a narrow orifice. All channels have a rectangular cross section and a height of 25 μm. (b) View of targeted lipospheres with gas in core and active ingredient in lipid oil complex [36].

#### *1.1.1.3. Drug delivery applications*

**Figure 3.** Assay design (a) The schematic workflow of the assay is pictured, starting from isolation of genomic DNA from cells, DNA amplification and on‐chip hybridization, respectively. (b) The location of KRAS codon 12 mutations within the amplicon and the corresponding capture probes is illustrated (ctr = positive control; wt = wild type; SNP =

Over the past decade, on‐chip diagnostic systems observed explosive growth and showed significant potential for clinical diagnostics specifically for diseases, including toxicity. The early, rapid and sensitive detection of the disease state is the prime objective for every on‐chip clinical diagnosis. Initially, this field was focused on developing the concepts of LOC and later evolved to applications in a number of biochemical analysis operations, such as clinical

In on‐chip diagnosis devices, apart from pregnancy detection kit and glucometer, most applications are based on genes and peptides detection for early indicators of disease [24–26]. For instance, Dinh et al describe a multifunctional biochip with nucleic acid and antibody probe receptors specific to the gene fragments of *Bacillus anthracis* and *Escherichia coli*, respectively [25]. These devices were based on the detection of specific diseases or biological warfare agents by incorporating biomarkers specific to such agents. Monitoring of regular metabolic param‐ eters, such as glucose and lactate, was demonstrated by the I‐Stat analyzer that provides point‐ of‐care testing for monitoring a variety of clinically relevant parameters [26]. Immunosensing

Recent years have witnessed a vast range of applications of LOC due to the significant benefits of small sample and reagent volume utilization, economic and rapid analysis with less wastage and possibility of developing disposable devices. Ahn et al. demonstrated a fully integrated

applications as a part of clinical diagnostics have also been demonstrated [27, 28].

single‐nucleotide polymorphism; SA‐HRP = streptavidin horseradish peroxidase) [20].

*1.1.1.2. On‐chip biosensing and disposable point‐of‐care devices*

82 Lab-on-a-Chip Fabrication and Application

analysis (blood gas analysis, glucose/lactate analysis, etc.) [23].

The major objective of drug delivery systems is to localize the pharmacological activity of the drug at the site of action as targeted drug delivery systems directly deliver the payload to the desired site of action with minimum interaction with normal cells. This phenomenon is especially important for anticancer drugs, as their toxicity to healthy cells is a cause of concern to improve therapeutic response and patient compliance. Last decade witnessed tremendous growth in targeted dosage forms for controlled release [33–35].

Approximately 10 million people suffer from different kinds of cancer per year and many of them unfortunately die due to lack of better treatment strategies. With the advancement in diagnostic, therapy techniques and nanomedicine, now better understanding of disease onset and treatment is possible, but still more will be offered by state‐of‐art microfluidic technology in terms of control over particle size, composition, encapsulation rate and better performance of nanoformulations, which have a great impact on the cancer survival rate.

In the series of microfluidics‐based delivery systems, a gas‐filled lipospheres was reported by Hettiarachchi et al. for targeted delivery of doxorubicin, using polydimethylsiloxane (PDMS)‐ based microfluidic chip that contained two distinct hydrodynamic flow‐focusing regions for local administration into tumor tissues as shown in **Figure 4a** [36]. Generally, liposomal‐ encapsulated doxorubicin suffers from relatively nonspecific biodistribution due to size selection and nontargeted accumulation [37]. As a solution, Hettiarachchi et al. prepared multilayer lipospheres with oil layer of triacetin (capable of carrying bioactive molecule) sandwiched between inner gas‐filled core and outer lipid layer (polyethylene glycol (PEG) lipid conjugate DSPE‐PEG2000‐Biotin) with avidin as targeting moieties based on the fact that multilayer gas‐filled lipospheres for high payload delivery at target sites could overcome the limitations of liposomal preparation. **Figure 4b** is representation of the modified delivery system.

Another strategy that is gaining importance in diagnosis and treatment of cancer is theranostic nanomedicine that combines imaging, diagnostic agent and antitumor agent. Theranostic lipid complex nanoparticles formed by bulk mixing do not give control over composition and size which can be overcome with a microfluidic setup [37, 38]. A static micromixer‐coaxial electrospray (MCE) for the single‐step synthesis of theranostic‐lipid complex nanoparticles (cationic lipid‐nucleic acid complexes called lipoplexes) was designed by Wu et al. to overcome this limitation. Multicriteria evaluation (MCE) technique produced monodispersed particles with a diameter of ∼194 nm and high encapsulation efficiency compared to a more conventional bulk process; the advantage of this process is shown in **Figure 5a**. Quantum dots (QD605) and Cy5‐labeled antisense oligodeoxynucleotides (Cy5‐G3139) were encapsulated as the model imaging reagent and therapeutic drug, respectively, with successful cytoplasm to delivery of drug into cytoplasm of A549 cells (nonsmall‐cell lung cancer cell line) leading to 48 ± 6% down regulation of the Bcl‐2 gene expression [37].

**Figure 5.** (a) Schematic drawing of the static micromixer‐coaxial electrospray (MCE) showing its various components [37]. (b) Schematic of microfluidic gradient generator [40].

A *microfluidic gradient generator* (MGG) was developed by Abhyankar et al. [39, 40] for testing drug response on a cellular basis. These devices offered unique features of, higher resolution, real‐time observation, tunable drug concentration and reduced costs in comparison with their conventional counterparts, Transwell and Dunn chambers. MGGs are based on two techniques —gradient achievement through time‐evolving diffusion or parallel streams mixing. **Fig‐ ure 5b** shows a sink‐source flow‐free gradient generator. The absence of convection flow is the key advantage of this system that eliminates the shear‐stress induced to cells.

Apart from nano‐based drug delivery techniques, administration of drug to the whole body is another application of microfluidics where miniaturized needles can be designed (*micronee‐ dles*) for improved delivery effectiveness and reduce the pain related to drug administering.

Microneedles can be classified into the following four general types: (i) solid microneedles, (ii) drug coated, (iii) polymeric microneedles with encapsulate drug that fully dissolve in the skin and (iv) hollow microneedles for drug infusion into skin.

#### *1.1.1.4. Microarrays technologies*

local administration into tumor tissues as shown in **Figure 4a** [36]. Generally, liposomal‐ encapsulated doxorubicin suffers from relatively nonspecific biodistribution due to size selection and nontargeted accumulation [37]. As a solution, Hettiarachchi et al. prepared multilayer lipospheres with oil layer of triacetin (capable of carrying bioactive molecule) sandwiched between inner gas‐filled core and outer lipid layer (polyethylene glycol (PEG) lipid conjugate DSPE‐PEG2000‐Biotin) with avidin as targeting moieties based on the fact that multilayer gas‐filled lipospheres for high payload delivery at target sites could overcome the limitations of liposomal preparation. **Figure 4b** is representation of the modified delivery

Another strategy that is gaining importance in diagnosis and treatment of cancer is theranostic nanomedicine that combines imaging, diagnostic agent and antitumor agent. Theranostic lipid complex nanoparticles formed by bulk mixing do not give control over composition and size which can be overcome with a microfluidic setup [37, 38]. A static micromixer‐coaxial electrospray (MCE) for the single‐step synthesis of theranostic‐lipid complex nanoparticles (cationic lipid‐nucleic acid complexes called lipoplexes) was designed by Wu et al. to overcome this limitation. Multicriteria evaluation (MCE) technique produced monodispersed particles with a diameter of ∼194 nm and high encapsulation efficiency compared to a more conventional bulk process; the advantage of this process is shown in **Figure 5a**. Quantum dots (QD605) and Cy5‐labeled antisense oligodeoxynucleotides (Cy5‐G3139) were encapsulated as the model imaging reagent and therapeutic drug, respectively, with successful cytoplasm to delivery of drug into cytoplasm of A549 cells (nonsmall‐cell lung cancer cell line) leading to

**Figure 5.** (a) Schematic drawing of the static micromixer‐coaxial electrospray (MCE) showing its various components

48 ± 6% down regulation of the Bcl‐2 gene expression [37].

[37]. (b) Schematic of microfluidic gradient generator [40].

system.

84 Lab-on-a-Chip Fabrication and Application

A microarray is an analytical device that comprises an array of molecules (oligonucleotides, cDNAs, clones, PCR products, polypeptides, antibodies and others) or tissue sections immo‐ bilized at discrete ordered [41]. In a general microarray device, sample solutions are confined in microfabricated channels and flow through the probe microarray area. Enhanced sensitivity is obtained due to high surface‐to‐volume ratio in microchannels of nanoliter volume and advantages of both fields can be exploited simultaneously by combining DNA microarray with microfluidics [42, 43]. Consumption of small volumes in microfluidic systems is an added advantage to develop low‐cost, compact and portable LOC systems. Secondly, the surface hybridization of target DNA can also be accelerated on microfluidics platform by electrokinetic delivery of negative charged DNA molecules on to the probe area [44].

Lee et al. proposed a recirculating microfluidic device for the hybridization of oligonucleotides to DNA microarray [45]. Peristaltic pump was connected to the both ends of the microchamber to generate circulatory flow as shown in **Figure 6a**. With this device, hybridization time was also shortened to 2 h and sample volume was 100 μL.

Many companies are involved in designing microfluidic technology for various high‐through‐ put applications, such as immunoassays, diagnostic devices, single molecule DNA and protein detection as well [42]. Researchers from the University of Chicago, USA, and other laboratories demonstrated the use of two‐phase droplet systems that generate droplets within microfluidic channels to be used as microreactors for high‐throughput screening of compounds and multiple chemical reactions [46, 47]. Recently, Huang et al. presented a microfluidic device integrated with pneumatically controlled microvalves and micropumps for parallel DNA hybridizations to analyze 48 different DNA targets (18‐mer oligonucleotides derived from the Dengue viral genes) simultaneously. A schematic of device is shown in **Figure 6b** [48].

**Figure 6.** (a) Diagram for sample recirculation system on the hybridization chamber and hybridization image of fluo‐ rescence‐labeled target nucleotide [45]. (b) *Left:* Photograph of the microfluidic chip containing shuttle‐flow channels, microvalves and micropumps. The shuttle flow hybridization was realized by controlling the gas ports 1, 2 and 3 auto‐ matically. *Right*: Hybridization specificity assay using four serotypes of Dengue virus under shuttle flow conditions (frequency 2 Hz) in channels. The duration of hybridization process was 90 s and washing time was 30 s [48].

The commercialization of microarray and microfluidic technologies is evolving very fast as demonstrated by the emergence of many start‐up companies due to its state‐of‐art technology. Affymetrix is an example where they generated a new market based on their GeneChip® technology over a 12‐year period.

#### *1.1.2. Challenges for lab‐on‐chip devices*

Apparently, microfluidics devices have the potential to serve different scientific needs of healthcare and biomedical sectors and as we discussed earlier, their several successful applications have already been reported. The major advantages associated with miniaturized systems are faster/more accurate diagnoses; better epidemiological data for disease modeling; vaccine introduction; and utilization of minimally trained healthcare workers and better use of existing therapeutics but still many hurdles are there in broader applications of microfluidics systems.

However, there is always a silver lining and due to vastly increased interest in global health issues, the current funding climate for the development of diagnostics kits is significantly good. Financial support for new and improved diagnostic tools for priority diseases, such as tuberculosis and cancer, is there. The Gates Foundation's Grand Challenges in Global Health initiative is supporting the development of prototypes of a disposable/hand‐held reader system [49]. Thanks to increased attention on the global health issues and the motivation for their better treatment, we are witnessing the beginning of microfluidics diagnostic devices for early detection of these fatal diseases in coming few years.

We started our discussion on the issues of need of miniaturized devices for pharma industry and biomedicine. After a brief overview on impact of existing LOC systems on global health, we discuss how the new emerging cells and OOC techniques will have an everlasting effect on different areas of human health. The latest progress in microfluidics has led to the devel‐ opment of OOC microdevices, which recapitulate the complex structure, microenvironment and physiological functionality of living human organs. The practical implementation of these miniature organ systems is revolutionary for the field of biomedical sciences and will play a pivotal role for drug discovery and will improve our understanding for mode of action of molecules of therapeutic potential—overall, this state‐of‐art technology is expected to be a boon for pharma and healthcare sector.
