Paper‐Based Digital Microfluidic Chip for Multiple Electrochemical Assay Operated by a Wireless Portable Control System

Abstract

The printing and modular fabrication of a paper-based active microfluidic lab on a chip implemented with electrochemical sensors (ECSs) is developed and integrated on a portable electrical control system. The electrodes of a chip plate for active electrowetting actuation of digital drops and an ECS for multiple analysis assays are fabricated by affordable printing techniques. For enhanced sensitivity of the sensor, the working electrode is modified through the electrochemical method, namely by reducing graphene with voltammetry and coating gold nanoparticles by amperometry. Detachable sensor and absorber modules are assembled modularly on an open chip plate, forming various novel hybridized open-closed chip formats. By varying the coupled or decoupled sensor modules, excellent detection of three diagnostic biological molecules is demonstrated (glucose, dopamine, and uric acid in human serum). With a newly designed portable power supply and wireless control system, the active paper-based chip platform can be utilized as an advanced point-of-care device for multiple assays in digital microfluidics.

Recent Advances in Microfluidic Paper-Based Analytical Devices toward High-Throughput Screening

“…Moreover, an electrical switching system (operation system) to activate each of the individual electrodes is required for the basic droplet manipulations of p-DMF devices. The inkjet method, a familiar printing method frequently used for handling fluids through EWOD, allows electrodes to be printed on paper in a very accessible way by using personal computers and printers ( Figure 4 a) [ 78 ]. On the printed electrode, as mentioned above, is a dielectric layer for preventing electrolysis; a parylene-C coating fabricated using chemical vapor deposition (CVD) is commonly coated with a hydrophobic layer that reduces the contact angle and increases the initial contact angle.…”

“…By decomposing the system into modules, which are sets of components with customized functions, one can reduce the system’s complexity. The system can be controlled by using computer-based software and a smartphone app ( Figure 4 c,d) [ 78 ].…”

“…The working electrode was modified with reduced graphene and Au NPs to enhance the sensitivity of the sensor. This hybridized open-close chip format demonstrated excellent multiplexed detection, which provided a wide linear range of low-level detection for three biological molecules in human serum [ 78 ]. During the fabrication step, a challenge for the design of the p-DMF device is the interference between the moving droplets and the voltages on the control lines because the electrode arrays and the control lines are printed on the same side of a paper sheet.…”

“…Research has been conducted using real samples, such as human serum, blood, and urine, for the detection of multiple analytes. The common biomolecules studied in clinical diagnosis, including glucose [ 159 ], lactate [ 160 ], and uric acid [ 78 ], have been successfully identified by using μPADs with colorimetric sensing as the main technique for detection. To improve the throughput and the sensitivity of μPADs, researchers have developed and constructed p-DMF devices for use as diagnostic platforms for highly sensitive detection of multiple biomolecules [ 78 , 80 , 135 ].…”

“… ( a ) A photograph of a p-DMF device, ( b ) schematic illustration fluid handling on the device, ( c ) a controlling system for operation of the p-DMF device, and ( d ) operation of the device to transport droplets. Reproduced with permission from the authors of [ 78 ]. Copyright 2017, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.…”