Debasis Dhal

Bio: Debasis Dhal is an academic researcher from University of Calcutta. The author has contributed to research in topics: Biochip & Mixing (physics). The author has an hindex of 3, co-authored 21 publications receiving 38 citations. Previous affiliations of Debasis Dhal include Assam University.

A technology shift towards triangular electrodes from square electrodes in design of Digital Microfluidic Biochip

Abstract: Digital Microfluidic Biochip (DMFB) is a ground-breaking invention in many areas of Microelectronics, Biochemistry, and Biomedical sciences. It is also known as ‘Lab-on-a-Chip’ for its performance as an alternative for laboratory experiments. Various types of diagnosis procedures are performed on it through a sequence of modular operations like sample preparation, mixing, and detection. Mixing is the most important operation of DMFB as the outcome of the experiment is almost dominated by mixing. A good mixing of corresponding sample and reagent gives proper result while an improper mixing leads to erroneous result, which may be the reason to discard the assay. So, our objective is the betterment of mixing operation. In this paper, we have proposed a design using equilateral triangular electrodes instead of square electrodes, maintaining all the constraints required to ensure safe droplet movement and other modular operations, while improvement of the mixing operation is the key design issue.

A Design of Digital Microfluidic Biochip along with Structural and Behavioural Features in Triangular Electrode Based Array

Abstract: Digital microfluidic based biochip manoeuvres on the theory of microfluidic technology, having a broad variety of applications in chemistry, biology, environmental monitoring, military etc. Being concerned about the technological advancement in this domain, we have focused on equilateral triangular electrodes based DMFB systems. Accepting the associated design issues, here, we have addressed many facets of such electrodes regarding their structural and behavioural issues in comparison to the existing square electrodes. As the requisite voltage reduction is a key challenging design issues, to implement all the tasks using triangular electrodes that are possible in square electrode arrays as well, is a tedious job. Furthermore, to deal with this new design deploying triangular electrodes, we have analyzed all the necessary decisive factors including fluidic constraints to ensure safe droplet movements and other modular operations together with mixing and routing. Moreover, an algorithm has been developed to find a route for a given source and destination pair in this newly designed DMFB. Finally, we have included a comparative study between this new design and the existing one while encountering the above mentioned issues.

A generalized algorithm for solving n coins problem

Abstract: Eight coins problem is a well-known problem in mathematics as well as in computer science. In this problem eight coins are given, say A, B, C, D, E, F, G, and H, and we are told that only one is counterfeit (or false), as it has a different weight than each of the others. We want to determine which coin it is, making use of an equal arm balance. At the same time we want to identify the counterfeit coin using a minimum number of comparisons and determine whether the false coin is heavier or lighter than each of the remaining. In this paper, we develop algorithms for solving the counterfeit coin problem for any given number n of coins. The first algorithm is in essence based on the existing classical solution for the eight coins problem (with slight modification) for larger values of n, where n is a power of two beyond eight, as two and four being base cases. Then we develop an algorithm for solving n coins problem, where n is even but not power of two, i.e., the numbers are six, ten, 12, 14, 18, 20, etc. At the end, we have extended the same to solve the counterfeit coin problem for odd number of coins as well.

Enhancement of mixing operation through new movement strategies in digital microfluidic biochips

Abstract: Microfluidic biochip is a lab-on-a-chip system that replaces conventional laboratory experiments. Digital Microfluidic Biochip (DMFB) handles liquids as discrete droplets, and offers highly reconfigurable and scalable technology. DMFB combines electronics with biology opening the new application areas of Microelectronics, Biochemistry, and Biomedical sciences. A new application area of DMFB using equilateral triangular electrodes instead of square electrodes has been proposed, considering the design issues and the fluidic constraints while performing all the modular operations. The improvement of sample-reagent mixing procedure is a key challenge issue in bioassay implementation as mixing is the most dominating operation in DMFB; hence, the Triangular DMFB (TEDMB) system leads over the existing DMFB system. In this paper, we have presented a study of TEDMB mixers and developed mixing library for TEDMB synthesis.

An Algorithm for Parallel Assay Operations in a Restricted Sized Chip in Digital Microfluidics

Abstract: Digital Microfluidic Biochips (DMFB) is revolutionizing many areas of Microelectronics, Biochemistry, and Biomedical sciences. It is also known as 'Lab-on-a-Chip' for its popularity as an alternative for laboratory experiments. Pin count reduction and cross contamination avoidance are some of the core design issues for practical applications. Nowadays, due to emergency and cost effectiveness, more than one assay operations are required to be performed simultaneously. So, parallelism is a necessity in DMFB. Having an area of a given chip as a constraint, how efficiently we can use a restricted sized biochip and how much parallelism can be incorporated are the objectives of this paper. The paper presents a design automation flow that augments parallelism in applications considering cross contamination problem as well.

Advances in Testing Techniques for Digital Microfluidic Biochips

Abstract: With the advancement of digital microfluidics technology, applications such as on-chip DNA analysis, point of care diagnosis and automated drug discovery are common nowadays. The use of Digital Microfluidics Biochips (DMFBs) in disease assessment and recognition of target molecules had become popular during the past few years. The reliability of these DMFBs is crucial when they are used in various medical applications. Errors found in these biochips are mainly due to the defects developed during droplet manipulation, chip degradation and inaccuracies in the bio-assay experiments. The recently proposed Micro-electrode-dot Array (MEDA)-based DMFBs involve both fluidic and electronic domains in the micro-electrode cell. Thus, the testing techniques for these biochips should be revised in order to ensure proper functionality. This paper describes recent advances in the testing technologies for digital microfluidics biochips, which would serve as a useful platform for developing revised/new testing techniques for MEDA-based biochips. Therefore, the relevancy of these techniques with respect to testing of MEDA-based biochips is analyzed in order to exploit the full potential of these biochips.

Development of advanced operators for enhanced on-chip biosensing in digital microfluidic platforms

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Beyond high voltage in the digital microfluidic devices for an integrated portable sensing system

Abstract: Digital microfluidics (DMFs) show great potential in the fields of lab-on-a-chip applications for electro-chemical as well as biochemical sensing for decades. Various types of DMF devices have been demonstrated to improve their capabilities such as smaller device size for portability, higher reliability, and multi-purpose applications, etc. Among them, the electrowetting on dielectric (EWOD) is one of the most widely used mechanisms to manipulate droplets due to its good flexibility. On the other hand, the high-voltage application that required for EWOD-type DMF also limits the portability and dimension of the whole system. In this review, we discuss the DMFs which are powered by alternative sources other than electrical sources and evaluate their potential for future portable biochemical assays. Then, the demonstrations reported with the possibility beyond high voltage are discussed starting from lowering voltage requirement for EWODs to the unique methods using mechanical, optical, and energy harvesting to power DMF devices. Finally, the practical applications and prospective on the integrated multi-functional lab-on-a-chip applications are tackled.

Electrowetting-on-Dielectric Based Economical Digital Microfluidic Chip on Flexible Substrate by Inkjet Printing

Abstract: In order to get rid of the dependence on expensive photolithography technology and related facilities, an economic and simple design and fabrication technology for digital microfluidics (DMF) is proposed. The electrodes pattern was generated by inkjet printing nanosilver conductive ink on the flexible Polyethylene terephthalate (PET) substrate with a 3D circuit board printer, food wrap film was attached to the electrode array to act as the dielectric layer and Teflon® AF was sprayed to form a hydrophobic layer. The PET substrate and food wrap film are low cost and accessible to general users. The proposed flexible DMF chips can be reused for a long time by replacing the dielectric film coated with hydrophobic layer. The resolution and conductivity of silver traces and the contact angle and velocity of the droplets were evaluated to demonstrate that the proposed technology is comparable to the traditional DMF fabrication process. As far as the rapid prototyping of DMF is concerned, this technology has shown very attractive advantages in many aspects, such as fabrication cost, fabrication time, material selection and mass production capacity, without sacrificing the performance of DMF. The flexible DMF chips have successfully implemented basic droplet operations on a square and hexagon electrode array.

On the complexity of design tasks for Digital Microfluidic Biochips

Abstract: Digital Microfluidic Biochips (DMFBs) is an emerging technology aiming at the automatic processing of biological assays. Experiments are conducted by routing droplets of liquids on a grid. Determining a routing is the first step in the design process. A particular routing is carried out by actuating the cells of the DMFB grid in a certain manner. These actuations are controlled by microcontrollers having a limited number of output pins. Thus, it is usually not possible to control each cell separately, but multiple cells have to share a common control pin leading to the pin assignment problem. In recent years, a wide range of heuristic as well as exact approaches has been proposed to solve these problems. While the NP -completeness of routing and pin assignment has already been conjectured in the literature, we present the first actual proofs. Thus, the use of general-purpose approaches like SAT solvers is indeed justified. We additionally prove the NP -completeness for variants of the routing problem.