Nanofluidics for single molecule manipulation and sensing
Related Projects
Nano Particle experimental
Nano particles (NPs) have the potential to improve the way many diseases are detected and treated, for example providing new strategies for the detection of disease bio-markers, drugs and gene delivery and for the cure of cancer. Developing effective NP-based solutions to such biomedical applications requires that the NPs operate in serum and other complex biological media. This also implies the ability to perform accurate measurements of the NPs’ properties such as size and zeta-potential.
Among the methods for particle counting and sizing. resistive pulse probably is the most popular method. With the advancement of Lab-on-a-chip technologies, microfluidic and nanofluidic RPS sensors with high sensitivity and accuracy were developed. Besides the basic functions for particle sizing, counting and measuring particle’s zeta-potential, a nano-RPS sensor can also characterize nano particles, DNA, viruses, antigens and so on. Such advancements greatly enrich the powerful abilities of the RPS technology and make the development of a low cost and portable flow cytometer possible.
Microfluidic and nanofluidic RPS employ the principle of the Coulter counter in microfluidic or nanofluidic channels for particle counting and sizing. The working principle and typical system setup is shown in Figure below. For the system shown in Figure, an electrical field is applied across a sensing orifice whose size is much smaller than the main channel which is filled with an electrolyte solution. Each particle passing the sensing orifice will generate a resistive pulse which is processed by the amplification circuit, the data acquisition device, and the computer. Each particle will generate one signal pulse and the magnitude of the signal represents the volume ratio of the particle and the sensing gate. In this way, particle sizing and counting are achieved.
Simulation Studies
Nanopore based sensors have been used in vast areas of scientific and manufacturing industries, including medical diagnostic, energy, and environment fields. Nanopore based sensors have been explored for detection and analysis of biological and chemical molecules (such as DNA and proteins), biophysical investigations of nanoparticles and polymers, ion-selective filtering, and water desalination. Today because of progress in different nanopore fabrication methods and also the advantages of nanopore-based sensors, including low cost, fluid-based, high sensitivity, and small required sample volume, these sensors have attracted lots of attention. One of the most applicable nanopore-based sensors is the resistive pulse sensor. The sensing process by resistive pulse sensing (RPS) method is running by characterizing the variation of the ionic current, which causes when the targeted nanoparticle translocates through the nanopore. Size, surface charge, and concentration are the basic physical parameters of nanoparticles, which can be characterized by the RPS method. We have used numerical simulation as a powerful tool to investigate the parameters that affect the ionic current through the nanopore. In this study, the modeling and simulation of the resistive pulse in RPS method have been developed and validated by other experimental results. The effects of major parameters, including nanopore and nanoparticle size and surface charge on nanopore resistivity, have been quantitatively analyzed. There are several solid-state nanopore platforms that have been used in RPS method. In this research, the pulse amplitude, duration, and resolution of RPS platforms are compared numerically, which can be helpful to specify the advantages of each platform.