Computational Design of a Single Heater Convective Polymerase Chain Reaction for Point-of-Care

Recently, researchers have started working to develop polymerase chain reaction (PCR) devices as a means for point-of-care (POC) applications. Among the requirements are portability, affordability, and performing reliably and quickly. Proposed by the present study is a process to design a convective-PCR (CPCR) device with only a single heater. It is assumed that such a design developed using microfluidics and capillary tube should help make a CPCR to be portable and more economical for POC use. One of the challenges is to achieve steadily the prerequisite three temperature zones with a single heater. It is demonstrated that this can be done with the present methodology. The underlying physics of the convection driving the CPCR function is mathematically modeled, then verified by our experimental results. In search of better designs, the following parameters that affect the CPCR performance are considered: the heater's height, and the diameter, the height, and the wall thickness of the capillary tube. A large design space consisting of design candidates is defined by combining the values within the range of each of these parameters. The results of the corresponding design cases are obtained from our mathematical model, and the performance of each case is evaluated by their deoxyribonucleic acid (DNA) doubling time. The two best CPCR performing reactors are selected and discussed. It is, therefore, demonstrated that the present methodology is capable of enhancing the CPCR reactor performance with a single heater.

Analysis of efficiency of convection in porous geometries (square vs triangular) with multiple discrete heaters on walls

PurposeThe purpose of the paper is to study natural convection within porous square and triangular geometries (design 1: regular isosceles triangle, design 2: inverted isosceles triangle) subjected to discrete heating with various locations of double heaters along the vertical (square) or inclined (triangular) arms.Design/methodology/approachGalerkin finite element method is used to solve the governing equations for a wide range of modified Darcy number,Dam= 10−5–10−2with various fluid saturated porous media,Prm= 0.015 and 7.2 at a modified Rayleigh number,Ram= 106involving the strategic placement of double heaters along the vertical or inclined arms (types 1-3). Adaptive mesh refinement is implemented based on the lengths of discrete heaters. Finite element based heat flow visualization via heatlines has been adopted to study heat distribution at various portions.FindingsThe strategic positioning of the double heaters (types 1-3) and the convective heatline vortices depict significant overall temperature elevation at bothDam= 10−4and 10−2compared to type 0 (single heater at each vertical or inclined arm). Types 2 and 3 are found to promote higher temperature uniformity and greater overall temperature elevation atDam= 10−2. Overall, the triangular design 2 geometry is also found to be optimal in achieving greater temperature elevation for the porous media saturated with various fluids (Prm).Practical implicationsMultiple heaters (at each side [left or right] wall) result in enhanced temperature elevation compared to the single heater (at each side [left or right] wall). The results of the current work may be useful for the material processing, thermal storage and solar heating applications.Originality/valueThe heatline approach is used to visualize the heat flow involving double heaters along the side (left or right) arms (square and triangular geometries) during natural convection involving porous media. The heatlines depict the trajectories of heat flow that are essential for thermal management involving larger thermal elevation. The mixing cup or bulk average temperature values are obtained for all types of heating (types 0-3) involving all geometries, and overall temperature elevation is examined based on higher mixing cup temperature values.

On the Liquid Film Flow Characteristics During the Rewetting in the Single Rod Air-Water System

Dry-out and rewetting phenomenon may occur on a fuel rod surface during anticipated operational occurrences (AOOs) for a boiling water reactor (BWR). The conventional rewetting model included in the current system code tends to underestimate the rewetting propagation velocity due to the absence of an appropriate precursory cooling model. The present research aims at the development of a mechanistic model for the precursory cooling in the annular mist flow regime typical of AOO and anticipated transition without scrum (ATWS). Rewetting experiments were carried out using a single heater rod in the circular glass pipe with air-water flow at atmospheric pressure to visualize the rewetting behavior and obtain mechanistic understanding on the phenomena. This paper summarizes the experimental results and discusses the liquid film flow characteristics including roll wave formation and spattering at the rewetting front.

Fabrication of 3D continuous-flow reverse-transcription polymerase chain reaction microdevice integrated with on-chip fluorescence detection for semi-quantitative assessment of gene expression

A 3D microdevice equipped with a portable pump and a single heater was fabricated integrating RNA amplification and detection functionalities.

Fabrication of a 3D Teflon microdevice for energy free homogeneous liquid flow inside a long microchannel and its application to continuous-flow PCR

The 3D spiral PTFE microdevice was fabricated for performing continuous-flow PCR using a single heater and via semi-automated sample injection method.