Hardware Design: Design Proposal and Functional Prototype
In order to solve some real environmental challenges, our team has proposed an integrated system that can both detect and degrade endocrine disrupting chemicals (EDCs) suitable for farmland water protection.
When we started building this system, we aimed not only to solve a few farmers’ problems but on a bigger scale, agricultural and industrial, since in most of the developing countries, factories could be easily found in between farmland. On the left-hand side of the flowchart, we developed the system that could sense the concentration of the EDC in the water and control the valve to protect the farmland from polluted water. And on the right-hand side of the flowchart, we could collect such data, such as the concentration, time, and place. If the number of devices could grow to dozens or even hundreds, we would be able to tell where and when did the pollution came from.
In general, the gate will remain half-open and let the water comes into the channel. When the water passes through the gate, it will then passes through the filter. Enzyme mixed with activated carbon is filled in the filter, which can help filter out most of our target endocrine disrupting chemicals. We have proved the capability of the enzyme and filter through the modeling and experiment test. Then the water will encounter our fluorescent detection device. We pump some water into the detector and mix them with the indicator paper which is coated with modified E. coli, and the EDCs in the water can be captured by our modified E. coli. The E. coli is later excited with laser light to produce fluorescent, the fluorescent (whose) signal will be collected and calculated into relative EDCs concentration.
If the detected EDCs concentration is safe for the farmland to use, the microcontroller which is embedded in the detector will send a signal to the gate to tell it to remain open to let the water in. However, if the detected EDCs concentration is above the safety standard, a feedback signal will be sent to the gate and lower it to protect the farmland from further damage. The reading of the EDCs concentration will also be sent to our database and the App, which can allow the farmer or the farmland manager to remotely monitor the condition of the farmland.
Filter Design: Functional Prototype
Our target is to make the filter have the best efficient and longest lifetime. In the design, we use different pore size material to protect our core enzyme, so that it will not be damaged by other particles, and extending the filter lifetime. The front part of the filter is composed of polypropylene fiber, the back end of the filter is filled with activated carbon, which is mixed with the enzyme that can degrade our target endocrine disrupting chemicals. As for the outer shell, it is made of a layer of steel net and galvanized iron. A Solidworks filter sketch is provided underneath.
Before making the functional prototype, our wet and dry lab members conducted enzyme kinetics modeling to know the degradation speed and time, also a concentration test is performed to know the activated carbon’s EDC absorbing ability. Both modeling and test sure positive result, for further details, please check out the Model page under the Project category. Some prototype photos are provided underneath, too.
Fluorescence Detector: Design Concept and Current Lab Result
Our design filer has proven to be capable of degrading the endocrine disrupting chemicals (EDCs) in the water. However, there are more situations needed to be considered. For example, when factories illegally emit wastewater that contains a high concentration of EDCs, it may exceed the degradation capability of our filter, and the farmland could then suffer serious damage. Also when typhoon approaches, the heavy muddy water can severely contaminate the growing environment of the crops. Thus, it is important to isolate such water flowing into the farmland. Hence we proposed a design of the fluorescence-based EDCs detector, that can detect the concentration of EDCs, and automatically controls the gate depending on the feedback signals sent by the detector.
The core of the fluorescence-based EDCs detector lies on the chip which we designed to capture EDCs for the water sample. The mechanism behind it is to modify the E. colis expression of GFP and ER-alpha. EDCs will combine with ER-alpha, causing the structure of ER-alpha to change. And then monobody will capture the bounded ER-alpha together with E. coli, leading to the change of fluorescence or surface plasmon resonance signal on the gold chip and we can thus estimate the concentration of EDCs. Despite there are still some technical challenges for us to tackle, for instance, the transforming of GFP into E. coli. We have been able to detect BPA and NP concentration as low as 5µM (about 1 ppm) in the water.
Here we introduce the mechanical design proposal of our fluorescence-based EDCs detector. The mechanism of the fluorescence-based EDCs detector works as follow: First installed the biochip into the detector. Turn on the detector’s microcontroller (MCU) and mini water pump. The pump will periodically suck water and flow through the biochip A laser light will excite the E. coli ’s GFP gene on the biochip and send out fluorescence. The fluorescence will pass through an optical filter then be received by our light detector. The program in the MCU will calculate the fluorescence light into relative EDCs concentration If the concentration is lower than the safety standard, the MCU will not send a signal to the gate; if the concentration is higher than the safety standard, a feedback signal will be sent to the gate to close it in order to protect the farmland.
The water gate in our model is controlled by a step motor, and the screw bar in the middle of the gate enable the step motor to control the rising and lowering of the gate. The mechanism of the rising and lowering depends on the EDCs concentration sensed by our fluorescence-based EDCs detector. When the EDCs concentration exceeds the safety value or the flow rate is too fast, the microcontroller in the detector will automatically send out a control signal to lower the gate to protect the farmland.