Electrowetting-on-dielectric (EWOD): Current perspectives and applications in ensuring food safety

Abstract

Digital microfluidic (DMF) platforms have contributed immensely to the development of multifunctional lab-on-chip systems for performing complete sets of biological and analytical assays. Electrowetting-on-dielectric (EWOD) technology, due to its outstanding flexibility and integrability, has emerged as a promising candidate for such lab-on-chip applications. Triggered by an electrical stimulus, EWOD devices allow precise manipulation of single droplets along the designed electrode arrays without employing external pumps and valves, thereby enhancing the miniaturization and portability of the system towards transcending important laboratory assays in resource-limited settings. In recent years, the simple fabrication process and reprogrammable architecture of EWOD chips have led to their widespread applications in food safety analysis. Various EWOD devices have been developed for the quantitative monitoring of analytes such as food-borne pathogens, heavy metal ions, vitamins, and antioxidants, which are significant in food samples. In this paper, we reviewed the advances and developments in the design of EWOD systems for performing versatile functions starting from sample preparation to sample detection, enabling rapid and high-throughput food analysis.

Advances in Microscale Droplet Generation and Manipulation

“…With a vision to enable better integration of various sensors and actuators, an open-chip EWOD platform has been developed. An oil-covered compound droplet scheme is used to address the evaporation and contamination issues . Fundamental functions such as droplet merging, mixing, and splitting have been demonstrated.…”

“…The generation and manipulation of larger millimeter-sized (microliter) droplets are essential for many biomedical applications. − In this size range, digital microfluidic devices using electric fields are appealing due to their simple design and capability to work with small sample volumes. , The manipulation of the millimetric-size droplet is usually performed through various electric and magnetic platforms. , Droplet actuation using DC or low-frequency (Hz) electric fields on dielectric-coated electrodes is termed electrowetting on dielectric (EWOD) . Electrowetting has been explored for multiple applications because it enables programmability, reconfigurability, and the realization of portable hand-held systems .…”

Merging microfluidics with luminescence immunoassays for urgent point-of-care diagnostics of COVID-19

“…Droplet formation includes active and passive ways. The active approach applies an external force to microfluidics, including opto-electrowetting [ [250] , [251] , [252] ], magnetism [ [253] , [254] , [255] ], thermocapillary forces [ 256 , 257 ], surface acoustic waves [ [258] , [259] , [260] ], dielectrophoresis (DEP) [ [261] , [262] , [263] ], electrowetting-on-dielectric (EWOD) [ [264] , [265] , [266] ], etc. However, these methods are suitable for manipulating droplets but not for massive droplet generation to meet digital immunoassays.…”

Development of a Microfluidic Chip Powered by EWOD for <em>In Vitro</em> Manipulation of Bovine Embryos

“…The technology employs applied electric fields [44] to manipulate pico-to micro-liter (10 -12 -10 -6 L) droplets in a rapid manner on an array of insulated electrodes on the chip [45][46][47]. Plentiful examples of EWOD based microdevices created for chemistry and life sciences exist [48][49][50][51][52][53][54]. A novel direction for EWOD in ARTs was proposed recently, allowing for the analysis of spent culture medium from a single human embryo with no interference to the culture protocol, which is unachievable using standard techniques [55].…”