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Detecting cancer biomarkers at an early stage at the clinical level has been the interest of numerous researchers over the years due to its impact on recovery. Therefore, attention is towards fabricating reliable, cost-effective, reproducible, and accurate devices for point-of-care screening. This review aims to highlight the emerging field of memristive biosensors and compare it to similar electrochemical devices used for cancer biomarker detection. The limit of detection (LOD) achieved by memristive biosensors was generally in the femtomolar (fM) range in comparison to field effect transistors (FET) and electrochemical immunosensors, which in most instances exhibited a LOD in the picomolar (pM) and nanomolar (nM) range. Most current memristive biosensors are fabricated using silicon nanowires, which calls for exploring different materials and structures that may lower fabrication complexity and increase reproducibility. This article examines the working principle of memristors for biosensing, the biofunctionalization of antibodies, the interaction between antibodies and antigens and its influence on memristors, as well as fabrication processes and applications of memristors for biosensing. This paper will report on memristor-based biomedical sensors focusing on cancer screening. In addition, the outlook of reduced graphene oxide (rGO) as an active material for sensing will be discussed. Memristors are anticipated to enhance the future of sensing due to their great sensitivity and simplicity of fabrication.

Two-dimensional numerical simulations for heated and unheated flows over two circular cylinders of different diameters in tandem are conducted. The study is conducted for Re = 150 and temperature ratio 1 ≤ (T* = Ts/T∞) ≤ 2.3. The study is limited to spacing ratios in the range 2 ≤ L/Dd ≤ 8 and diameter ratios 0.5 ≤ Du/Dd ≤ 2. The effect of heating on the flow is captured by modelling the thermophysical properties of the fluid fitted as polynomial functions of temperature. The flow features are visualized by plotting the streamlines and velocity magnitude contours. These flow patterns are also discussed based on the reattachment and co-shedding regimes which are classification found in literature. The effect of varying geometrical parameters on the flow in terms of change of regime is discussed. Furthermore, the drag coefficient (Cd) on both upstream and downstream cylinders is presented as a function of spacing and diameter ratios. Additionally the average surface heat transfer coefficient (h) is presented for the interval of spacing and diameter ratios stated. Results show that the presence of an upstream cylinder led to reduction of Cd on the downstream cylinder to a value lower than that of single cylinder for all cases studied. Heating both cylinders causes Cd on both cylinders to become less sensitive to a change in L/Dd, and increasing Du/Dd is found to decrease h on both upstream and downstream cylinders.

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Heated and unheated flows with forced convection over two fixed circular cylinders in tandem are studied numerically for 80 ≤ Re ≤ 250 and 1 ≤ T* ≤ 2.3. Three different spacing ratios (L/D) = [2, 4, 8] are considered under three heating conditions. The scenarios considered are (1) heated upstream and unheated downstream cylinders, (2) unheated upstream and heated downstream cylinders and (3) heated upstream and downstream cylinders. These scenarios represent the limiting case for a cross-flow heat exchanger, where the downstream tubes are at increasingly lower or higher temperature for cooling or heating, respectively. The global aerodynamic forces on the cylinder as vortices shed was investigated. The flow is visualized by plotting the streamlines, temperature fields, and velocity magnitude contours for the different spacing ratios and compared to the flow regimes in literature namely, Extended-body, Reattachment, and Co-shedding regimes. The drag and surface heat transfer coefficients are analyzed for different scenarios. The effect of heating on the fluid properties and the resulted wakes in the flow are found to be strongly influenced by Re and L/D. The scenario of heated upstream and unheated downstream cylinders was found to increase the mean drag coefficient Cd on the upstream cylinder for L/D = 2 & 4 but is not as evident for the downstream cylinder. The heat transfer coefficient h on the upstream cylinder remained approximately the same regardless of a heated or unheated downstream cylinder. In contrast, h of the downstream cylinder decreases for the scenario of heated upstream and downstream cylinder.