Humans can drink seawater into fresh water has always been a thankless job, it is energy consumption, water quality is poor, MIT scientists have now manufactured chip can better accomplish the job.
Although more than 70% of the Earth's surface is covered by water, but we can use the water but not too much.glue stick The bitter sea salt accounted for 97.5% of the total amount of water, fresh water and most of the rest concentrated in the North and South poles and glaciers. Millions of years, humans can only rely on only 0.2% of the total water of fresh water to survive.
Seawater into fresh water is the subject of a long history. Although as early as 1954, people built a large-scale desalination plants, but so far, the most common way is still the desalination of sea water reverse osmosis semi-permeable membrane or multi-level flash. The former use of the water molecules to pass through the membrane to prevent other impurities, while the latter decreased by several times to let the water pressure in the form of rapid escape of steam. glue gun This is higher than the cost of two ways, and are not suitable for manufacturing into a portable desalination unit. Now researchers at MIT and South Korea have created a chip can be used for desalination of seawater for desalination provides a new idea.
The chip is produced with the traditional way of integrated circuit chips, similar to simple photolithography and etching process can be completed. It can increase the concentration of salts in seawater, and discharged through a passage, a passage from another fresh water produced is quite good. It is based on a technique called ion concentration polarization (ICP, IonConcentrationPolarization) to achieve this phenomenon of desalination process, and its impressive feature low power consumption: 1,000 liters of fresh water manufacturers, only 3.5 kWh.
Ion concentration polarization is a power to the electrolyte solution, the phenomenon occurs. When the electrodes had high current, the electrode closer to those from the ion will be close to the opposite electrode, and the distant ion in the solution and added too late to create a layer on the electrode outside the lower ion concentration in the solution layer. This phenomenon in the process of electrolysis and electroplating is harmful because it implies the need for stronger currents or stirring frequently to reduce the uneven distribution of the negative ion effect; and developed at MIT that water chip, but just use a thin layer of low concentration of this solution - it means high-quality fresh water.
Massachusetts Institute of Technology Institute of Electronic and Electrical and Computer JongyoonHan postdoctoral SungJaeKim and teaching assistants and their South Korean colleagues on a postage stamp-sized soft silicon substrate to create a device of this separation of fresh water. Tiny chip was Y shaped channel, the middle of the intersection is the separation of salt and fresh water at, and the V-shaped ground connected. After the addition of 75 volts, the water flows through the water channel into the intersection will be split: a high concentration of the solution will be discharged through the export of salt, but one can gather from the mouth of that layer of fresh water with low concentration of the solution.
This technology is the key to channel width and voltage. If the width is too wide, then the low concentration solution of the electrode surface, that is, we need a mixture of salt water with fresh water will be discharged; and narrow width, it will result in energy waste, and reducing the amount of water. Now in this prototype chip, and into the water channel width is 0.5 mm, the width of each outlet is only 0.25 mm, the depth of 0.1 mm. It is an exciting test results.
In the test, the researchers first Ipswich in Massachusetts to obtain water samples from the Crane Beach, in which blood cells added, some debris and other waste material to make this more consistent with the actual situation of sea water, and then use filters to channel diameter of more than filter out impurities, and then water access this chip. Under a microscope you can clearly see that half a second after power, muddy water in the Y-channel cross the intersection of action, clear water to fresh water exports, while high concentrations of salt water more turbid flow of salt water port.
Experiments confirmed that this method has been able to remove 99% of sea salt and other impurities, the total output of fresh water in the half. Of course, this method can only be used to remove charged ions and impurities, for electrically neutral particles, it does not apply. Output of fresh water from the mouth such as activated carbon filtration still need to deal with in this way, it can become a safe drinking water. "The chip can be sea water and brackish water separated from bacteria and other particles, and will not have any congestion." JongyoonHan said, "This is what the U.S. might not be a big problem. But in India, many of the drinking water are is brackish water or salt water, this feature becomes very important. "
Now, the water purification process and the cost of the chip has not a big problem, after all, photolithography and etching technology in the decades to become a mature development process, researchers are more concerned about its efficiency. In the laboratory products, because the channel capacity limit of water per minute into the 0.02 ml and 0.01 ml water production only. This means that if an adult to meet drinking water needs of 4 liters a day, a chip need to work 9 months.
Large quantities of these chips will be integrated together, it may be a better way. The researchers have now to create a panel of 100 water purification units to verify the large-scale integration of the results on the impact of desalination, and try to complete a water purification unit that contains 10,000 of the system. In the ideal case, such a system can produce 6 liters of fresh water per hour, enough to support a medium-sized families.
In remote areas and underdeveloped areas, this desalination plant will be able to use electricity generated by solar cells to run, just to the top of water poured from the device to connect with the help of gravity, from the bottom to collect water. It could also be a good tool for disaster relief will also need a portable desalination unit for other occasions to help. However, in this bright future in front of the chip still need to go through large-scale integration of experiments and testing through in order to determine whether it really is worth promoting. The researchers believe that the scale and improve the process takes about two years. Taking into account the lack of water on the planet is facing difficulties, two years, no doubt can wait.