Team:Bolivia/Hardware
The hardware device arose out of a necessity to provide the required conditions to adapt our biosensor to rural communities since it will provide the necessary conditions for the reading of results and transport mainly, in areas where it is difficult to access this type of technology, the characteristics of this device (FADSR) have been divided into the following points:
Device operation
I. The purpose of the device
The fast arsenic data sample reader (FADSR) is a mechatronic device capable of measuring color produced by an engineered bacteria that acts as a biosensor to detect arsenic. This device holds 18 spaces to analyze different samples in an accurate and reproducible way. The device also retains the engineered bacteria (biosensor) within and prevents it from escaping to the external environment. The information obtained can be observed by the operator in real time as well as by being transmitted wirelessly, which makes it very accessible for extraction of the results obtained. In addition, this device contains batteries that give it a useful life without the need of a continuous power supply. It is worth mentioning that the material is resistant to weathering and light weight. All of these functional characteristics make this device suitable for field work, as it was inspired by iGEM Peshawar's 2017 MAX (Metal Alert Xystem) design.
Figure 1.The design model for the device contains the general parts of the FADSR design where dynamics and assembly are demonstrated...
How does the device work?
The operation of the device is divided into the following stages:
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Loading the water samples in the respective samples box previously designed in a 3D printer with measurements already established.
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Once all the water samples to be analyzed have been placed, there will be a limit switch sensor that will detect that the device's lid is in its respective place to start sampling them. With the samples in their respective places and the lid in the right place, there will be a start button to begin with the beginning of the reading of the samples.
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By having three different compartments, it will be possible to choose the way manual if you want to work with one, two or three of the compartments, depending on the number of samples to be analyzed.
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Once the samples have been read, the results of the samples will be displayed, indicating with a lead on the device and the results will also be stored digitally as obtained in the readings of each sampling.
Figure 2.Electronic Circuit Used
II. Hardware functionality
The FADSR (fast arsenic data sampler reader) has an aluminum chassis that makes it resistant, light and compact. The acrylic / wood coating allows the device to be fully removable. The mobile part that makes synchronized analysis possible consists of a mechanism formed by 3 rotating discs driven by stepper motors, these driven discs move 6 sample containers each with them. The 3 sensors (Color Sensor TC230) make it possible to analyze the different batches simultaneously. In the event of any event, the device has a stop button per motor. The indicators on the control panel show the results for each disc. 001110, with 0 being positive and 1 negative depending on the position of the sample on the disk.
Figure 3.The functionality of the device is reflected in two parts, the mechanical part and the electronic part, and they complement each other.
The materials to be used for the construction of the external part of the equipment will be mainly aluminum “L” profiles for the structure and 1.5 mm Acrylic for the walls and protection from external agents inside the equipment . Several 3D impressions will also be used, such as the individual sample trays, since these will have a much lower depth than a traditional petri dish, which will give us greater reliability of the sensor reading.
III. PARTS ASSEMBLY LIST:
| ELEMENT | PART NUMBER | PART | DSCRIPTION |
|---|---|---|---|
| 1 | TRAYS | IN CHARGE OF CARRYING THE PETRI BOXES FOR LOADING SAMPLES | |
| 2 | CASE | WITH THE PURPOSE OF PROTECTING BOTH MECHANICAL AND ELECTRONIC COMPONENTS OF THE DETECTOR | |
| 3 | ALUMINUM SKELETON | STRUCTURE ON WHICH THE HOUSING WILL BE MOUNTED | |
| 4 | NEMA MOTOR ASSEMBLY | MOTORS IN CHARGE OF GENERATING ROTATIONAL MOVEMENT IN THE TRAY | |
| 5 | COLOR SENSORS TCS 230 | SENSOR IN CHARGE OF READINGS THE COLOR OF THE SAMPLES | |
| 6 | ARDUINO MEGA 2560 AND ARDUINO CNC ASSEMBLY | IT WILL CONTROL ALL PROCESSES REQUIRED FOR THE ACTION AND GENERAL OPERATION | |
| 7 | BUTTON MICROSWITCH-RED | RESET / SHUTDOWN OF THE ELECTRONIC DEVICE | |
| 8 | DISPLAY COUNTER | IT WILL COUNT THE NUMBER OF SAMPLES GIVEN | |
| 9 | LCD SCREEN | WILL DISPLAY ARSENIC MEASUREMENT DATA AND LEVELS | |
| 10 | MENBRANE | IT WILL CONTROL SPECIFIC ACTION GIVEN ACCORDING TO REQUERIMENTS | |
| 11 | PETRI OWN BOXES | HOLDS THE SAMPLES FOR POST-MEASUREMENT |
FUTURE WORK FOR THE DEVICE
1. GENERAL PROPOSAL
Considering aspects of the importance of taking data in real time, it is essential to be able to carry out arsenic measurements in situ, and since well or wastewater waters consist of different composition characteristics (Total solids, and other ionic agents that may interfere with the detection of arsenic) (Escalera Vásquez, 2014)a pretretting process must be carried out before measuring arsenic, with this process we will be able to carry out the in situ measurements of arsenic without any interference from the water source.
Since on average wastewater or well water contains high amounts of total solids, there must be a first step for the filtration of particulate materials, which we will call a primary filter, we will also require an absorbent for ions that can compete with Arsenic or that may interfere with the measurement of Arsenic, thus, a second filter is required for the removal of other ionic agents.
After the pre-treatment process, the water sample will require an incubator, because the lyophilized biosensor in filter paper must be immersed in the water sample to be sensed, and then incubated for at least 18 hours at 36°C, for the generation of chromoproteins, which will give a characteristic color, which will allow us, thanks to our device, measure arsenic concentration.
2. EQUIPMENT DESIGN
2.1 PRIMARY FILTER DESIGN
The objective of the initial filter is the removal of foreign bodies with respect to the observation analyte, without altering the presence of this, so that it can be identified in filter 2. For this purpose, the bibliographic review (Escalera Vásquez, 2014) studied indicates that the primary filter must retain a significant percentage of large substances such as total solids and others, on the other hand, in this filter micro and nanoparticulate material is deposited, others of biological and chemical material in smaller quantities.
The primary filter will be made up of a small hollow cylinder made of polypropylene with holes along the surface to allow passage to the flow of water. The filter surface would allow a coating of 3.5cm long by 0.8cm wide of a stainless steel mesh that contributes to the retention of larger particulate matter (Reyes, 2014). The filter size parameters are detailed below:
Table 1. General parameters of the primary filter
| Parameter | Description |
|---|---|
| Long | 2.05 cm |
| Inner diameter | 0.86 cm |
| Outer diameter | 0.63 cm |
Figure 1 Primary filter design: stainless steel filter N°100
Source : Own elaboration
A mesh will be needed to coat the primary filter whose material must be stainless steel N°100 which ensures high corrosion resistance and consequently long life. These meshes will be used for: i) their ease of cleaning and maintenance, ii) filtration capacity, iii) resistance to oxidation in the presence of acids or other chemical agents (Reyes, 2014). The characteristics of this mesh are detailed below:
Table 2. Specific parameters of mesh N°100
| Parameter | Description |
|---|---|
| D: Wire diameter in mm | 0.1 mm |
| w: Distance between 2 contiguous wires | 50 mm |
| Mesh length | 34.4 mm |
| Mesh width | 17.75 mm |
| Mesh area | 610.6 mm2 |
Source: Adapted from(Reyes, 2014)
A second stage of the primary filter will consist of a cylindrical filter with an adsorbent material of micro and nanoparticles as well as chemical and biological agents. For the selection of this material, a table was made to be able to select the best material:
Table 3. Material comparison for the primary filter
| MATERIAL | ADVANTAGES | DISADVANTAGES |
|---|---|---|
| Activated carbon | i) Absorbent material that removes organic matter(BOD5), total suspended solids (OSH), organic compounds among others, ii) Easy access in the market | i) Can remove As and other heavy metals. ii) Saturation in the pores, decreasing the efficiency of the system. |
| Cotton | i) Absorbent, ii) High tear resistance, iii) Smooth texture, iv) Does not accumulate static electricity, v) Does not retain metals, vi) Degradable, vii) Low cost. | ii) Not reusable |
| Paper or fabric filters | i) Porosity, ii) High solids holding capacity iii) Moisture resistant, iv) Flow rate. | Requires pre-treatment |
Source: Adapted from(Reyes, 2014)
Given the characteristics mentioned in the table above, a matrix of commercial cotton fibers was selected. The criteria used for this selection are as follows: i) It is an absorbent material of great utility in the retention of solids for water samples taken in situ, ii) can be functionalized for the selective retention of heavy metals; iii) does not have retention of As (when it is not activated as will be demonstrated),iv) is a low-cost material with easy access in the market,v) is easy to handle vi) is a material of easy degradation, the latter being one of the main criteria for selecting materials for the configuration of the pretreation system since it has a low environmental impact on living beings. According to the results obtained by (Reyes, 2014),the effectiveness of cotton fibers as a material to filter water in a first phase is verified, without changing or modifying the arsenic concentration values and contributing to the retention of ionic species such as mercury and lead. It is also worth mentioning that it retains a significant amount of particulate matter, but it is insufficient to eliminate the interference factors, so it is necessary to act on a second filter that we call secondary.
Figure 2. Primary filter design: cotton filter
2.2 SECONDARY FILTER DESIGN
Activated carbon is a material widely used for water purification and filter design. The microporous morphology of activated carbon gives it a high specific area, although limitations may occur due to blockage of micropores during adsorption processes. This could drastically reduce the service life in the operating conditions of the pre-treatment system developed in this work, since it would require regeneration of the same. Biochar, especially chemically modified biochar such as MnOX charged biochar, bismuth impregnated biochar and biochar colloid, has a high adsorption capacity of heavy metals.
Figure 3. Secondary filter design :biocarbon filter
Source : Own elaboration
The volume of the biochar column reactor shall be 565 mL (diameter: 6 cm, height: 20 cm). The Biochar column will be filled with 20 g of biochar impregnated with bismuth (height: 10 cm) and quartz sand at the top and bottom.
The biochar filter considerations to be taken into account are: rapid saturation at flow and high competitive ion concentrations, in addition to the effect of temperature and pH on actual wastewater treatment (Silvetti et al., 2017)
2.3. INCUBATOR
The incubator to be developed will be a prototype laboratory incubator, which will consist of a temperature-controlled heat resistance, for the incubation of our biosensor in the water sample (Córdoba Baule, 2019). The instruments required for data collection are as follows:
Table 4. Instruments for incubator design
| Instrument | Feature |
|---|---|
| Controller 58008 | Device capable of controlling the temperature produced by the electrical resistance and sensed through thermocouples |
| Thermocouple Type J | It is a temperature sensor whose maximum reading range is 450°C, this is used for the reading of the temperature within the prototype produced by the electrical resistance |
| Arduino Platform | Software used for programming the Arduino Nano microcontroller for the control and reading of the electronic devices connected to it. |
| Heat resistance for incubator | 110V 80W |
Source : Own elaboration
The Incubator will have an internal chamber and an external chamber, the first built of galvanized steel and covered with epoxy paint, the second built with stainless steel.
Figure 4. Incubator prototype camera area
Source: Adapted from (Córdoba Baule, 2019)
As for the power required for the operation of the incubator, the operating temperature must be taken into account, which will be 36°C; and the power required by the heat resistance, which is proposed to be 80W. Taking into account that the operating period will be 16 hours per day, the corresponding calculation was made where a total required power of 1.28 kw / hour was obtained, this data is of vital importance since with this a power battery must be selected that satisfies this requirement, and in order to promote the use of renewable energies, a solar panel will be used together with a storage battery that meets the calculated power requirement.
BIBLIOGRAPHY:
Córdoba Baule, D. E. (2019). Design and construction of a prototype microbiological incubator.
Escalera Vásquez, R. (2014). PRESENCE OF ARSENIC IN DEEP WELL WATERS AND THEIR REMOVAL USING A PILOT PROTOTYPE BASED ON LOW-COST SOLAR COLLECTORS. scielo.
Reyes, Y. (2014). Portable pretretting system to assist nanosensors with in situ detection and quantification of water samples. 85. Silvetti, M., Garau, G., Demurtas, D., Marceddu, S., Deiana, S., & Castaldi, P. (2017). Influence of lead in the sorption of arsenate by municipal solid waste composts: metal(loid) retention, desorption and phytotoxicity. Bioresource Technology, 225,90-98.