Recent Progress in Lab-on-a-Chip Technology and Its Potential Application to Clinical Diagnoses

Abstract

We present the construction of the lab-on-a-chip (LOC) system, a state-of-the-art technology that uses polymer materials (i.e., poly[dimethylsiloxane]) for the miniaturization of conventional laboratory apparatuses, and show the potential use of these microfluidic devices in clinical applications. In particular, we introduce the independent unit components of the LOC system and demonstrate how each component can be functionally integrated into one monolithic system for the realization of a LOC system. In specific, we demonstrate microscale polymerase chain reaction with the use of a single heater, a microscale sample injection device with a disposable plastic syringe and a strategy for device assembly under environmentally mild conditions assisted by surface modification techniques. In this way, we endeavor to construct a totally integrated, disposable microfluidic system operated by a single mode, the pressure, which can be applied on-site with enhanced device portability and disposability and with simple and rapid operation for medical and clinical diagnoses, potentially extending its application to urodynamic studies in molecular level.

Keywords: Diagnosis; Disposable equipment; Lab-on-a-chip devices; Micro-electrical-mechanical systems; Miniaturization; Polymers.

Fig. 1

Unit components making up the lab-on-a-chip (LOC) system.

Fig. 2

(A-D) 3 dimentional (3D) continuous-flow polymerase chain reaction (PCR) microdevice. (A) A photo of a microdevice placed on a single heater. (B) Continuous up-and-down movement of a colored ink solution inside a 3D microchannel. (C) Height-dependent temperature distribution with the use of a single heater at the bottom. (D) Result of agarose gel electrophoresis displaying 230 bp target amplicon amplified from pGEM-3Zf(+) plasmid vector. (E-G) Qiandu-shaped microdevice for performing continuous-flow PCR. (E) A photo of a microdevice. (F) Temperature distribution measured on the slanted surface when placed on a single heater. An imaginary white line was drawn to show the position of the microchannel. (G) Enlarged serpentine microchannel on which one complete thermal cycle (denaturation and annealing/extension) is defined.

Fig. 3

Scheme and result demonstrating sample injection employing a disposable plastic syringe. (A) A schematic illustration showing a spiral microchannel fabricated with poly(dimethylsiloxane) (PDMS) and placed on two heating blocks for performing continuous-flow polymerase chain reaction (PCR). (B) A photo showing sample flow inside a spiral microchannel actuated by a disposable plastic syringe. (C) Result of agarose gel electrophoresis amplifying a 230-bp target amplicon from the pGEM-3Zf(+) plasmid vector. Target band intensities were comparable when performed off-chip and on-chip.

Fig. 4

(A) Schematic illustration demonstrating the mechanism for bonding poly(dimethylsiloxane) (PDMS) and plastic substrates, independently grafted with either aminosilane or epoxysilane, under room temperature and atmospheric pressure condition. A strong amine-epoxy bond is formed after 1 hour of physical contact resulting in permanent assembly. (B) Results of physical detachment of the bonded assemblies and colored ink flow inside the bonded microchannel.