A Lab-on-a-Chip (LOC) device, also known as a micro-total-analytical system (microTAS) or microfluidics device, is a device that can integrate miniaturized laboratory functions (such as separation and analysis of components of a mixture) on a single microprocessor chip using extremely small fluid volumes on the order of nanoliters to picoliters. From a technology categorization perspective, LOCs can be viewed as a subset of microelectromechanical systems (MEMS) and combine miniaturized or novel sensing systems, fluid flow control concepts from microfluidics, and the suite of fabrication techniques (such as material deposition, material removal, surface patterning, and electrical property modification) used by the semiconductor industry. Currently, the main commercial applications of LOCs are in the medical and biotechnological fields, where it is anticipated that developments so far are the heralds of a technological revolution. In the same way that miniaturization changed computers from machines of limited capabilities occupying large rooms to small and easily portable yet powerful technology of today, over a period of a few decades, medical, biotechnological, and chemical analysis is expected to move from room-sized laboratories to microchipbased devices housed in hand-held or small portable readout consoles. Figure 28 shows an example of an LOC device that was tested on the International Space Station in 2007.
Figure 28: LOC device tested on the International Space Station in 2007 At the heart of LOC devices are “chips”, ranging in size from a fingernail to a credit card, fabricated using processes adapted from the printed circuit industry such as lithography, chemical etching, and laser machining. Figure 29 illustrates an impression of the size of the chip. Figure 30 provides a functional diagram of LOCs.
Figure 29. A comparison of the size of LOCs
Figure 30. Functional diagram of LOCs In a manner similar to the production of printed circuit boards using techniques such as embossing and molding, microstructures (such as channels for liquid flow and pits for mixing and reactions) are made on the chip by depositing layers of material on top of one another on a surface, then patterning and selectively removing material to form a feature. A flat top surface or lid is attached to enclose the channels or mixing pits, and reagents can be driven around the system by pneumatic, electromotive, or capillary systems. The LOC was first conceived by Michael Widner at Ciba-Geigy (now Novartis) in the 1980s, described conceptually in 1990 (Manz et al. 1990) with a groundbreaking work being published in 1992 (Harrison et al. 1992). Further development occurred as a new area of discovery—microfluidics—was developed in the 1990s. Microfluidics is an
interdisciplinary field dealing with the behavior and control of extremely small volumes of fluids and the design of systems that use these small volumes. Though most commonly encountered in ink-jet printers, the vast majority of microfluidics applications have been in biotechnology research, and some experts even regard it as a branch of biotechnology. In some ways, Microfluidics parallels nanotechnology in that the behavior of fluids at the microscale can differ substantially from the behavior at the macroscale; phenomena such as surface tension, heat conduction, and fluidic resistance start to become important, and issues such as evaporation, absence of turbulent flow, and the threat posed by presence of air bubbles are critical to system design. Initially, much of the impetus for continued development of LOCs came from the Human Genome Project, a 13-year project coordinated by DOE and the National Institutes of Health (NIH) that began in 1990 and was completed in 2003. Currently, much of the impetus for the continued development of LOCs comes from the desire for point-of-care medical diagnostics, whether in the doctor’s office, on a...
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