Optical flocculation technique based on optogenetic and whispering gallery modes for drinking water purification

摘要

In this paper, we develop dielectric micro-optical sensors based on whispering gallery mode phenomenon (WGM) for monitoring and treating of drinking water environments through two phases. Some sort of chemical impurities could be toxic and carcinogenic to humans and animals. The biogeochemical reactions are governing the chance and the movement of these impurities in the drinking water environment. Based on that, the first phase in this paper will focus to measure and quantify the concentration of these impurities in the water medium. While the second phase will exploit the use of the light based on the same phenomena (WGM) to create water treatment and purification using a nano charged dielectric polymeric beads. In the current paper, a high-resolution micro-optical sensor concept is used to detect these chemical impurities. The sensing element is a silica microsphere acts as an optical resonator. The proposed technique aims to provide preliminary results demonstrating the practical success of these sensors for effective monitoring of chemical impurities concentrations and contaminants which can cause serious kidney damage and possibly death. The second phase is basically depend on the optogenetic approach which is a biological technique that involves the use of light to control cells in living tissue, typically neurons that have been genetically modified to express light-sensitive ion channels. In this approach, the beads will be coated with a photosensitive protein called channelrhodopsin. This protein is a subfamily of retinylidene proteins (rhodopsins) that function as light-gated ion channels. They serve as sensory photoreceptors in unicellular green algae, controlling phototoxic: movement in response to light. The nano coated beads then poled for +4hrs under 1MV/m. When these nano charged beads mixed with water that have high turbidity, the beads starts to attract the colloids in that water. Since, the beads are coated with a photosensitive protein so by using a specific wavelength of the light we can control the motion of the spheres inside the water. Using a pulse width modulation (PWM) algorithm to control the speed of switching on/off the light; so it becomes easy to control the nano beads. The higher duty cycles for the PWM the charged beads makes the colloids aggregate and come together in a very short time (< 5 min) compared to the typical flocculation approaches that needs (~55min). This approach is called an optical flocculation technique and it shows one order of magnitude enhancement in the flocculation time. Results indicate that the WGM based-sensors are sensitive enough to refractive index changes in the case of liquid media (water). Experiments were carried out to validate the analysis and to provide an assessment of this sensor concept. Also, Preliminary experiments were carried out to provide an assessment of this concept using more than one duty cycle to control the speed of the beads. Results shows that we can purify the drinking water in time less than 3 minutes under 80% duty cycle using this approach.