Microfluidic Systems
The ready market availability of porous membranes with cylindrical pores of 15-200 nm and a thickness of 6-10 ìm facilitates the development of three dimensional analytical unit operation devices on an attaLiter scale. By employing these membranes as gates at the interface of two crossed microfluidic channels, the rate and direction of the fluid exchange can be controlled with electrical potential, polarity, solution ionic strength or diameter of the nanocapillary1. The microfluidic channels, fabricated by soft lithography, have been used for a decade. Dr. Paul W. Bohn, Centennial Professor of Chemical Sciences at the University of Illinois at Urbana-Champaign, sees the advance to multilayered liquid chromatography as a key step in the development of micro total analysis systems (ìTAS), which would involve such new applications as injection, collection, mixing, switching and detection. Recently he has been studying the analyte responses to various constraints applied to the system and its deviations in behavior from that of a similar system on the macro scale.
Microfluidic channels are a convenient and durable means of fluid transport made of poly(dimethylsiloxane) (PDMS), a common polymer with non-polar side groups. PDMS is durable, highly flexible and elastic, oxygen permeable and very hydrophobic2. It also has negative surface charge density at pH 81. The method of soft lithography allows for rapid deposition of complex crossed two dimensional fluid pathways on a silicon wafer.
The membrane containing these nanopores is a 6 – 10 micron thick polycarbonate nuclear track-etched membrane (PCTE) that has been coated with poly(vinylpyrrolidone) (PVP) to make it hydrophilic. This coating results in a pH of 8 in the system3. The pores in the membrane are cylindrical and of diameters in the range of 15 – 200 nm. The size of these pores are of the same order of magnitude of the Debye length (ê-1) of the ionic interactions in solution (1 nm < ê-1 < 50 nm) when the ionic strength is in the millimmolar range1.
The small physical character of the nanopore allows for a change in ionic strength of the solution to be sufficient to alter the interaction between the solution and the nanopore. By merely changing the concentration, the nature of the flow induced by electrical potential can be switched between electrophoresis and electro osmosis1.
The direction of the flow can be controlled by the size of the nanopore. At large pore sizes, the negative surface charge density on the microfluidic channel caused by the slightly basic pH of the system
Craig, D. Q. (2002). Pharmaceutical Applications of Micro-Thermal Analysis. Journal of Pharmaceutical Science, 91(5), 1201-1213.
In the diagram below on the right, we see two solutions divided by a partially/selectively permeable membrane (i.e. one that is porous, but allows water molecules through faster than dissolved substances). Text Box: Originally, the two solutions were; pure water, on the left, and sugar solution with a high sugar concentration, on the right. The pure water solution is said to have higher water potential than the concentrated sugar solution, because the water will flow from the area of high concentration of free water molecules (the dilute solution), to the area of low concentration of free water molecules (the concentrated solution). In other words, to the sugar solution.
If the concentration of one side of the membrane is greater than the molecules will travel from the higher to lower concentration. Eventually there will be a dynamic equilibrium and there will be no net movement of molecules from one side to the other. Osmosis is the diffusion of water. Like diffusion, the water moves from a region of higher water potential to a region of lower water potential.
...lications in the future. This is due to the fact that this method has become rough, not complicated and it can be performed in a conventional way without being mandatory the investigation into depth for every application (Tetala and van Beek, 2010). New forms are going to be operated in order to recognize bacteria and also aptamers are going to be used more often. Moreover, the investigation of new types of monoliths will also include the study of present or alterative types of polymers, in order to come out with a wider range of pore sizes, surface areas and new morphologies that can be used in this type of affinity chromatography (Pfaunmiller et al., 2013). Finally, monolithic stationary phases are expected to have a great impact on future applications, for instance if organic monolithic supports will be combined with hybrids of silica (Pfaunmiller et al., 2013).
In my case, I use up a box of tampons, depending on the flow of my menstruation. I would throw them out in the garbage bin, along with its plastic applicator. I never imagined that one tampon could leave a great impact on the environment. Women would produce 62,415 pounds of garbage worth of tampons in her lifetime. (EPA, 2017) These tampons would also end up in landfills which will take longer to decompose because of its dense fiber product. (Bridle & Kirkpatrick, 2004) The little plastic applicators can also cause a detrimental effect on the marine ecosystem, as they can travel to long distances. (Ashley et al,. 2005) They could confuse the plastic applicators as food. (Sheavly & Register, 2007) In regards to its production, a tampon is cotton based. The cotton used is genetically modified and inorganic to increase the production rate. (Chow, 2015, para. 9) These can cause impacts to the species living in the surroundings, and to the women using it as
The direction of osmosis depends on the relative concentration of the solutes on the two sides. In osmosis, water can travel in three different ways. If the molecules outside the cell are lower than the concentration in the cytosol, the solution is said to be hypotonic to the cytosol, in this process, water diffuses into the cell until equilibrium is established. If the molecules outside the cell are higher than the concentration in the cytosol, the solution is said to be hypertonic to the cytosol, in this process, water diffuses out of the cell until equilibrium exists. If the molecules outside and inside the cell are equal, the solution is said to be isotonic to the cytosol, in this process, water diffuses into and out of the cell at equal rates, causing no net movement of water. In osmosis the cell is selectively permeable, meaning that it only allows certain substances to be transferred into and out of the cell. In osmosis, the proteins only on the surface are called peripheral proteins, which form carbohydrate chains whose purpose is used like antennae for communication. Embedded in the peripheral proteins are integral
When a positive and a negative electrode are placed in a solution containing ions, and an electric potential is applied to the electrodes, the positively charged ions move towards the negative electrode, and the negatively charged ions to the positive electrode. As a result, an electric current flows between the electrodes. The strength of the current depends on the electric potential between the electrodes and the concentration of ions in the solution. Ionization is the formation of electrically charges atoms or molecules.
Dialysis tubing is made from regenerated cellulose or cellophane, and is used in clinical circumstances to ensure that molecule have a filtered flow, and that larger solute molecules do not enter the dialysis tubing (Alberts, 2002). Like a cell membrane, dialysis tubing has a semi-permeable membrane, which allows small molecule to permeate through the membrane. Thus, the dialysis tubing mimics the diffusion and osmosis processes of the cell membrane (Alberts, 2002). Although the dialysis tubing has a semi-permeable membrane, which mimics a cell, its structure is different. The me...
The electrolyte (solution) contains negative and positive ions. For electrolysis to work there must be the same amount of positive ions to negative ions so that the solution is electrically balanced. A solution of metal compounds can only conduct electricity if it is balanced. The negative ions are attracted to the anode (+ve electrode) and the positive ions (protons) are attracted to the cathode (-ve electrode). The electrolyte effect the amount of atoms attracted.
Nick Bilton starts “Artificial Intelligence as a Threat” with a comparison of Ebola, Bird flu, SARS, and artificial intelligence. Noted by Bilton, humans can stop Ebola, bird flu, and SARS. However, artificial intelligence, if it ever exceeds human intelligence, would not be stoppable by humans. Bilton, in his article, argues that AI is the biggest threat to humans at our current time, more serious than Ebola and other diseases. Bilton references many books and articles which provide examples of threats of AI.
Micro Electro-Mechanical Systems (MEMS) is the integration of mechanical elements, sensors, actuators and electronics on a common silicon substrate using microfabrication techniques. MEMS are a hot area of research because they integrate sensing, analyzing and responding on the same silicon substrate hence promising realization of complete systems-on-a-chip. As MEMS are manufactured using batch fabrication techniques similar to IC technology, MEMS are expected to deliver high functionality at low prices.
PC-SK standard cation exchange membranes and PC-SA standard anion exchange membranes are used in the stack. Information given by the manu...
HPLC (High Performance Liquid Chromatography) is an analytical technique which separates a complex mixture of components into its specific individual components. It is a powerful tool in analysis, as it combines high speed with extreme sensitivity compared to traditional methods of chromatography because of the use of a pump which creates a high pressure and forces the mobile phase to move with the analyte in high speed. It is been used as a principle technology in various automated analyzers used for diagnostic purpose.
The overall purpose of the experiments in this lab was to introduce the function and structure of the plasma membrane, describe the workings of diffusion and osmosis, and to demonstrate how different factors such as particle size, temperature, and space of diffusion area affect the rate of diffusion. With the results from the experiments, it can be concluded that all of the factors listed do affect diffusion, and there may be many more than are unaccounted for.
There were many challenges that he had to face, when he decided to become a bodybuilder at the age of fourteen, he had to push himself very hard. He explains how he did not mind feeling pain during the process because he knew that without pain there will be no gain. He worked very hard and kept pushing himself. Many people did not support his