MEDA-Based Biochips: Proposed New Structural Testing Techniques for Fault Detection

I. Introduction

Lab-on-chip devices have been principally developed with an attention in the direction of automation of typical operations in laboratory within a miniaturized platform as alternative. These types of lab on chip devices are quite capable to handle the operation on microfluidic by making use of fluids like micro level volumes or nanolitre level volumes. The LoC devices for typical applications actually consist of DNA sequencing, immunoassays, sample preparation, point-of-care investigates, drug detection, and many more (Jebrail et al., 2012). The classification of microfluidic platforms has been made by the norm of droplet actuation or liquid propulsion for fluidic action, surface acoustics (Alistar et al., 2016) or electro kinetic, pressure driven and specifically capillary.

Continuous flow microfluidic biochips termed as the former generation of LoC devices. Which are consisting of pumps, micro fabricated channels, valves and actuators? Within a silicon or glass substrate these components are permanently etched. These devices are highly controlled in their functionality. Intended for a restricted class of applications they are employed. Designed for re-configurability in addition to higher scalability matters such type of lab devices may not found to be appropriate intended for complicated applications.

In comparison to continuous flow microfluidic biochips design, There is digital microfluidic biochip (DMFB) also considered to be as second cohort of LoC device. Which offers many advantages like reagent isolation, individual sample addressing and compatible with the array-based approaches for biochemical applications (Pollack et al., 2000)? Fluids are operated in the form of discrete droplets within a 2 dimensional array of electrodes in digital microfluidic biochips. For originating specified droplet actions the clock regulated electrical actuation systems are used. The specified droplet actions namely like transportation, mixing, merging, splitting, detection and dispensing. The inflection of interfacial tension amid an electrode and a conductive sample by applying electric field among them for carrying out droplet movements. For actuating the electrodes through the control sequences can be reconfigured within the same biochip concurrently for different bioassays. Electro wetting on Dielectrics (EWOD) for droplet actuation is considered to be one of the encouraging approaches. An imbalance of the Electro wetting on dielectric actuation force is developed on the droplet through application of electric field of the droplet to one side only. As a result it creates an interfacial tension incline. This interfacial tension is robust enough to move the droplet (Wang et al., 2014). Digital microfluidic biochip is typically built up with a 2-dimentional electrode array. For electrode actuation this 2-dimentional electrode array are fixed with peripheral devices specifically optical detector circuits, dispensing ports connected to required control pins and integrated logic.

Two dimensional microfluidic arrays comprise a set of basic cells containing of two parallel glass plates (Figure 1). Independently controllable electrodes in patterned array are used at the bottom plate. The top plate is coated with a continuous ground electrode. Silicon oil is used as the filler medium composed with the droplet under control which is sandwiched between the plates. Droplets could be stimulated along the predetermined path by independently adjusting the voltages on respective electrode inside the electrode array using the standard of electro wetting-on-dielectric has been mentioned earlier. The droplet shipping arrangement together by means of other microfluidic actions which are pre-programmed into a microcontroller. According to the actuation sequence of the corresponding electrodes the microcontroller drives the control pins.

Figure 1.

Schematic cross sectional view of DMFB