Fahmi Samsuri

Microfluidic hydrodynamic trapping for single cell analysis: mechanisms, methods and applications

The development of hydrodynamic-based microfluidic biochips has been increasing over the years. In this technique, the cells or particles are trapped in a particular region for single cell analysis (SCA) usually without any application of external force fields such as optical, electrical, magnetic or acoustic. There is a need to explore the insights of SCA in the cells natural state and development of these techniques is highly essential for that study. Researchers have highlighted the vast potential field that needs to be explored to develop biochip devices to suit market/researcher demands. Hydrodynamic microfluidics facilitates the development of passive lab-on-chip applications. This review gives an account of the recent advances in this field, along with their mechanisms, methods and applications.

Microfluidics-assisted photo nanoimprint lithography for the formation of cellular bioimprints

Morphology and surface features provide important markers for cell development and reaction to external stimuli. Bioimprint offers a technique for the permanent capture of these features into an UV-curing, biocompatible, methacrylate biopolymer. This material shows excellent replication fidelity and fast setting times. However, the minimum reproducible feature size depends on the skillful application of the liquid prepolymer. To enable the repeatable formation of high-resolution, structurally bioactive cellular bioimprints, a modified process based on the use of microfluidics for integrated cell culture and polymer delivery has been developed. In this article, the authors introduce the process and demonstrate its use for the culture and imaging of Ishikawa endometrial cancer cells. Transfer of a 100 nm thick Cr test pattern with micrometer-scale features into the biopolymer is demonstrated. Replication and atomic force microscopy imaging of imprinted cellular surface features with sub-50 nm resolution is shown. The process has applications in disease diagnostics, in drug discovery, and for the creation of biomimetic cell culture scaffolds.Morphology and surface features provide important markers for cell development and reaction to external stimuli. Bioimprint offers a technique for the permanent capture of these features into an UV-curing, biocompatible, methacrylate biopolymer. This material shows excellent replication fidelity and fast setting times. However, the minimum reproducible feature size depends on the skillful application of the liquid prepolymer. To enable the repeatable formation of high-resolution, structurally bioactive cellular bioimprints, a modified process based on the use of microfluidics for integrated cell culture and polymer delivery has been developed. In this article, the authors introduce the process and demonstrate its use for the culture and imaging of Ishikawa endometrial cancer cells. Transfer of a 100 nm thick Cr test pattern with micrometer-scale features into the biopolymer is demonstrated. Replication and atomic force microscopy imaging of imprinted cellular surface features with sub-50 nm resolution is ...

Formation of Nanoscale Bioimprints of Muscle Cells Using UV-Cured Spin-Coated Polymers

We report a nanoscale replication method suitable for biological specimens that has potential in single cell studies and in formation of 3D biocompatible scaffolds. Earlier studies using a heat-curable polydimethylsiloxane (PDMS) or a UV-curable elastomer introduced Bioimprint replication to facilitate cell imaging. However, the replicating conditions for thermal polymerization are known to cause cell dehydration during curing. In this study, a UV-cured methacrylate copolymer was developed for use in creating replicas of living cells and was tested on rat muscle cells. Bioimprints of muscle cells were formed by spin coating under UV irradiation. The polymer replicas were then separated from the muscle cells and were analyzed under an Atomic Force Microscope (AFM), in tapping mode, because it has low tip-sample forces and thus will not destroy the fine structures of the imprint. The new polymer is biocompatible with higher replication resolution and has a faster curing process than other types of silicon-based organic polymers such as PDMS. High resolution images of the muscle cell imprints showed the micro-and nanostructures of the muscle cells, including cellular fibers and structures within the cell membranes. The AFM is able to image features at nanoscale resolution with the potential for recognizing abnormalities on cell membranes at early stages of disease progression.

Modeling of Photovoltaic Solar Array under Different levels of partial shadow Conditions

Different methods of configuration have been formulated regarding photovoltaic solar power by employing several techniques. This has been done because of the varying conditions so that the loss of power can be minimized. The main factor which decreases energy output of the photovoltaic PV solar systems is partial shadowing. The way the energy output of partially shadowed arrays varies with the system configuration used, has been studied extensively. A huge degree of disorder still exists, particularly with respect to the best modularity grade for these systems. There are two distinct sub-divisions in the systems implemented in the reconfiguration mechanism: reconfigurable solar arrays, and a switching matrix to do a reconfiguration. Using different methods, the proportions of shadowing obstructions were noted to allow for calculation of the likely shadowing losses. The outcomes of this paper on modeling and monitoring are used to evaluate the photovoltaic system with respect to shadowing losses with different levels and their reliance on the system configuration are selected. It has been found that power loss because of varying conditions is majorly due to the decrease in radiance occurring on the photovoltaic array and can be avoided through selecting the suitable configuration and connection. The simulation results show that the output characteristics of the simulator presented better results with that proposed model.

The fabrication of microelectrode array biochip on PET using plate-to-plate NIL

Polyethylene terephthalate (PET) films are useful for various applications due to the characterization of PET were flexibility, thermal resistance and chemical resistant. PET Films are widely used in both commercial and industrial today since they are highly demand in the market. In this study, microelectrode array biochip was fabricated on flexible PET film using (plate-to-plate) nanoimprint lithography (NIL). The PET films acted as substrate while PDMS as the mould. The Polydimethylsiloxane (PDMS) mould was attached on top of the PET film and additionally clamped between two pieces of glass. A mild force was applied to it for REM (replica moulding). A study was carried out upon the surface profiling of the PDMS mould and PET to monitor the possibility of deformation after applying force upon the samples. The experiment shall present the finding of required force to REM the microelectrode array biochip pattern on the PET film.Polyethylene terephthalate (PET) films are useful for various applications due to the characterization of PET were flexibility, thermal resistance and chemical resistant. PET Films are widely used in both commercial and industrial today since they are highly demand in the market. In this study, microelectrode array biochip was fabricated on flexible PET film using (plate-to-plate) nanoimprint lithography (NIL). The PET films acted as substrate while PDMS as the mould. The Polydimethylsiloxane (PDMS) mould was attached on top of the PET film and additionally clamped between two pieces of glass. A mild force was applied to it for REM (replica moulding). A study was carried out upon the surface profiling of the PDMS mould and PET to monitor the possibility of deformation after applying force upon the samples. The experiment shall present the finding of required force to REM the microelectrode array biochip pattern on the PET film.

Replication of Muscle Cell Using Bioimprint

In our earlier study a heat‐curable PDMS or a UV curable elastomer, was used as the replicating material to introduce Bioimprint methodology to facilitate cell imaging [1–2] But, replicating conditions for thermal polymerization is known to cause cell dehydration during curing. In this study, a new type of polymer was developed for use in living cell replica formation, and it was tested on human muscle cells. The cells were incubated and cultured according to standard biological culturing procedures, and they were grown for about 10 days. The replicas were then separated from the muscle cells and taken for analysis under an Atomic Force Microscope (AFM). The new polymer was designed to be biocompatible with higher resolution and fast curing process compared to other types of silicon‐based organic polymers such as polydimethylsiloxane (PDMS). Muscle cell imprints were achieved and higher resolution images were able to show the micro structures of the muscle cells, including the cellular fibers and cell mem...

Skin cancer detection using non-invasive techniques

Skin cancer is the most common form of cancer and is globally rising. Historically, the diagnosis of skin cancers has depended on various conventional techniques which are of an invasive manner. A variety of commercial diagnostic tools and auxiliary techniques are available to detect skin cancer. This article explains in detail the principles and approaches involved for non-invasive skin cancer diagnostic methods such as photography, dermoscopy, sonography, confocal microscopy, Raman spectroscopy, fluorescence spectroscopy, terahertz spectroscopy, optical coherence tomography, the multispectral imaging technique, thermography, electrical bio-impedance, tape stripping and computer-aided analysis. The characteristics of an ideal screening test are outlined, and the authors pose several points for clinicians and scientists to consider in the evaluation of current and future studies of skin cancer detection and diagnosis. This comprehensive review critically analyses the literature associated with the field and summarises the recent updates along with their merits and demerits.

Design Optimization and Analysis of Proof Mass Actuation for MEMS Accelerometer: A Simulation Study

In this paper, we present the design and analysis of the proof mass for capacitive based MEMS accelerometers. A study was done to determine the parameters (length of hinge and number of combs) to be optimized for the MEMS accelerometer design. The proposed design can measure the acceleration in x-, y- and z-axes. The design features a proof mass with interdigitated fingers along each side. These interdigitated fingers act as parallel plate capacitors. Due to acceleration, capacitance changes along the comb drive. This change in capacitance can be used to monitor the acceleration. Analysis has been carried out with different comb width designs. Using the MEMS CAD tool CoventorWare, the structure has been designed, simulated and analyzed. The process flow for the fabrication has also been proposed for the above structure. Comparative study with several designs has been made and the efficient design parameters to be considered while designing MEMS accelerometer were proposed. Based on the study, a set of optimized design parameters for the comb accelerometer were reported.

Analytical modelling of sensing performance of carbon nanotubes for gas sensing

Carbon nanotubes (CNTs) have recently captured attention as novel materials for nanoelectronic sensors due to their ability to achieve better sensitivity and accuracy in these devices. Up until now, the majority of investigations have focused on experimental studies for sensors. Therefore, there is lack of analytical models comparative to experimental investigations. The proposed model employs a CNT-based field effect transistor (CNT-FET) scheme to model the transport parameters of the CNT-based gas sensor. The CNT conductance is affected on exposure to the target analyte – NH3 gas molecules. The NH3 gas concentration is absorbed on the CNT surface after a chemical reaction between the CNT and NH3. This modulates the current-voltage (I-V) characteristics and conductance of the CNT-based gas sensor. The I-V characteristics of the CNT-based sensor have been proposed as a criterion to detect the effect of gas absorption. Finally, the proposed model was compared with experimental investigation for validation.

Simulation of electric fields for the development of biochip for the purpose of manipulating biological cells

Researchers nowadays prefer biochip technology platform as a medium for conducting the analysis of biological cells where appropriate manipulation techniques like trapping, screening and sorting in a few seconds are required to perform biological cells analysis. Non-uniform AC electric field is required for dielectrophoresis force (DEP) to implement manipulation technique, where the non-uniform AC is generated by microelectrodes designed. The current design has a limitation in term of electric field distribution pattern generated. Thus, ring microarray microelectrode pattern was designed and simulated using COMSOL Multiphysics 4.4 software for implementing one of the main objectives of this study, which is to investigate the electric field distribution resulting from the microelectrodes designed. To optimize the generated DEP force for manipulating biological cells, electric field simulation is very important. The electric field simulation performed by altering some microelectrode geometric design parameters such as the microelectrodes length and the distance between the microelectrodes and the microcavity. The simulation has been shown in this paper. This is intended to simulate the effect of an electric field that results when there are any changes to the geometric design of microelectrodes. Based on the simulation that has been done, the results show the distance between the microelectrodes and microcavity provide more impact in electric field distribution strength compared to the change of the microelectrodes size.