Overview
In the field of synthetic biology, we often face the problem of long cell culture cycles and manpower. In order to reduce the workload of the experimenters, the researchers' energy is invested in the more important modules of the project, reducing the time required for project completion. Our team hopes to develop a culture machine that can monitor cell growth in real time and timely regulate the parameters required for cell culture, so as to keep the culture conditions such as temperature, Ph value, light intensity and nutrients in the most suitable range.
We envision that our hardware products are mainly based on modern biotechnology and automated control concepts, aiming to provide an efficient, accurate, safe, easy-to-use, and cheap microbial culture equipment to provide users with an efficient, smart, fast, and healthy culture environment, providing users with one-stop microbial culture services to meet the needs of different users. We call it a multifunctional microbial automatic culture machine. It is an intelligent hardware product that integrates intelligent cultivation, environmental monitoring, automated control, intelligent interaction and other functions. At the same time, it can also connect to the user's mobile phone, computer and other devices through intelligent cloud connection.
Below is our product vision
Hardware module design
To achieve this goal, we designed a total of four modules. The following is the detailed design process of our team's hardware modules
Processing control module: We use 51 microcontroller or Arduino as the core development board to connect the sensor module and feedback adjustment module, and then install the automation platform to realize the data processing and control function.
Sensor module: We have designed detection equipment for multiple environmental factors required for microbial culture, such as temperature, PH, weight, light, etc., and transferred their data to the core processing system to achieve better monitoring of microbial culture.
Feedback adjustment module: We use solid-state relays, PID temperature control equipment, PH adjustment fluid, adjustable light bulbs, pressure sensors and other equipment to perform multi-functional output of microbial culture media to meet the feedback adjustment conditions required by the culture environment.
Automation and interaction module: We will systematically combine all modules and realize flexible connection of each module on software and hardware to ensure the automatic integration of multi-functional microbial culture machine. At the same time, we will combine the design of the Internet of Things for software visualization and interaction. style control.
We choose safe, reliable, lightweight and affordable hardware materials for product design. This allows us to ensure that the product is fully functional while also making the product itself more convenient and grass-roots to meet the needs of multiple user groups. Therefore, it can be well adapted to the needs of individuals or organizations for efficient cultivation of a variety of microorganisms. Of course, we also use mathematical modeling and software design to make our projects more applicable to the real world.
Module 1: Processing Control Systems
Initially, 51 microcontroller was selected as the core development board.
51 microcontroller is the collective name for all microcontrollers compatible with the Intel 8031 instruction system. The ancestor of this series of microcontrollers is Intel's 8004 microcontroller. Later, with the development of Flash rom technology, the 8004 microcontroller made great progress and became one of the most widely used 8-bit microcontrollers. Its representative model is the AT89 series of ATMEL Company. It is widely used in industrial measurement and control systems. Many companies have launched compatible models of the 51 series, which will occupy a large number of markets for a long time to come. The 51 microcontroller is a basic one for entry-level microcontrollers, and it is also the most widely used one. It should be noted that 51 series microcontrollers generally do not have self-programming capabilities. 80C51 is a typical variety in the MCS-51 series; CMOS process microcontroller products developed by other manufacturers based on 8051 are collectively called the 80C51 series. Finally, we decided to choose Arduion UNO version
Arduino is an open source electronic prototyping platform with flexible, easy-to-use hardware and software. Arduino can receive input signals from various sensors to detect the operating environment, and affect its surrounding environment by controlling light sources, motors, and other drives. The microcontroller on the board is programmed using the Arduino programming language (based on Wiring) and the Arduino development environment (based on Processing).Arduino can run independently or communicate with software running on your computer (e.g., Flash, Processing, MaxMSP). The Arduino development IDE interface is based on open source code.
After conducting relevant experimental tests, we compared the functional differences between the above two hardware development boards in our project, and finally selected the tiny and convenient Arduino as the core processing board.
Module 2: Sensor
In the process of designing the multi-functional microbial automatic culture machine, we chose to use the pressure sensor to detect the weight of the microbial culture dish, the BH1750 light sensor to detect the light intensity in the microbial culture environment, and the MK-135 gas probe to detect the atmosphere and data sensing.
Pressure sensor
Each upper and lower surface has a strain gauge, and each strain gauge has two pressure resistors. A total of 4 pressure resistors, composed of a full bridge circuit. The full bridge circuit can improve measurement accuracy.
HX711AD module
Two I/O ports, corresponding to SCK and DOUT respectively. If DOUT=1, the ad converter is not ready to output data. When DOUT=0, it means that it is ready, and then you have to input pulses into SCK, and input a pulse, DOUT outputs a bit of data (binary, data from the highest bit to the lowest output), 24 pulses, and then according to the number of SCK pulses to choose the next working mode. We chose channel A, 128 gain.
Choice of working mode
The HX711AD module works in the following three modes: channel A 128 gain, channel B 32 gain, and channel A 64 gain. Corresponding to different gain, the full limit differential input signal amplitude is different.
Step1：change the number of PD_SCK pulses
The number of PD_SCK input pulses shall not be less than 25 and more than 27. Among them, the first 24 pulses are readings of the sensor output data.
The last 1~3 pulses are the choice of the next working mode of the sensor. See code tips below for specific changes.
Step2：Change Gapvalue
Gapvalue is an intermediate quantity, mass of heavy object = sensor reading value/Gapvalue
Select different working modes, the theoretical calculation value of Gapvalue will also be different due to different amplification factors (gains).
same. Probably Gapvalue = X0.86(2^24)/4.3, where X is a multiple of gain (see below for details)
Personal estimate: 128 gain—430 64 gain—215 32 gain—107
The above data are only so-called theoretical values, and the specific values need to be calibrated by yourself.
How to calibrate? (Take the Arduino program as an example)
First, make sure that nothing else is placed on the sensor; second, burn the program and open the serial monitor (you can also use the display, etc.). It can be seen that the mass of the heavy object printed on the serial monitor is 0; then, place a known mass on the sensor. items (such as 10 one-yuan coins, the total weight of which is about 62g), and then observe the serial port monitor value; compare the serial port monitor value with the actual mass of the item, and calibrate the Gapvalue value if there is an obvious deviation.
Basic principles explained
a. 5kg sensor (we can choose 5/10kg range)
Full-scale output voltage = excitation voltage * sensitivity 1.0mv/v. For example: the supply voltage is 5v times the sensitivity 1.0mv/v = full-scale 5mv. It is equivalent to generating a voltage of 5mV when 5Kg of gravity is exerted.
b. The 711 module samples the resulting 5mV voltage.
Overview: Channel A of the 711 module has a signal gain of 128 times, which can amplify the 5mV voltage by 128 times, and then sample and output the 24-bit AD converted value. The microcontroller reads out the 24-bit data through the specified timing.
pay attention:
Because the slope characteristic curves of different sensors are different, each sensor needs to correct the divisor of 4.30 here. When you find that the measured weight is too large, increase this value. If the tested weight is too small, reduce the change value. This value is generally between 4.0-5.0. Depends on the different linear slope of the sensor. Every sensor needs to be calibrated. If the sensor measurement value is too large, the value needs to be changed to a larger value. If the sensor measurement value is too small, the value needs to be changed to a small value.
Light detection module
BH1750 is a digital light meter that can measure the surrounding illumination. Compared with traditional photodiodes, BH1750 has the advantages of high measurement accuracy, simple circuit, and convenient data output. Therefore, it is widely used in smart homes, smart lamps, smart cities and other fields.
First of all, BH1750 can measure very accurate illumination values, with a measurement error within 10%. This is very important for scenes that require precise lighting control. For example, smart lamps need to automatically adjust their brightness according to the surrounding illumination value. The BH1750 can accurately measure the surrounding illumination value to achieve more intelligent control.
Secondly, the circuit of BH1750 is relatively simple. It only needs to communicate with other smart devices through the I2C interface, so that the illumination value can be output to other devices and controlled accordingly. This not only makes it easy to integrate illumination values into other smart devices, but also reduces the cost of the entire system.
In addition, the BH1750 has low power consumption and only requires 1lux of illumination to operate normally, making it an ideal choice for smart devices, especially in application scenarios that require low power consumption.
In short, as a digital illuminance meter, BH1750 has the advantages of high measurement accuracy, simple circuit, convenient data output, low power consumption, etc. Therefore, it is widely used in smart homes, smart lamps, smart cities and other fields, becoming an ideal choose.
PH detection module
Notice:
Please use an external switching power supply to keep the voltage as close to +5.00V as possible. The more accurate the voltage, the higher the accuracy!
The electrode needs to be calibrated with a standard buffer solution before each continuous use. In order to obtain more accurate results, the ambient temperature is preferably around 25°C. The known pH value must be reliable, and the closer the pH value is to the measured value, the better. . If the sample you are measuring is acidic, please use a pH 4.00 buffer solution to calibrate the electrode. If the sample you are measuring is alkaline, please use a pH 9.18 buffer solution to calibrate the electrode. Calibration is done in sections, just to get better accuracy.
Every time the pH electrode measures a solution with a different pH, it needs to be cleaned with clean water. It is recommended to use deionized water for cleaning.
In order to ensure measurement accuracy, it is recommended to use calibration solution to calibrate the pH meter regularly to prevent large errors. Calibration is generally performed once every six months. If the measured solution contains many impurities, it is recommended to increase the number of calibrations!
Steps for usage:
(1) Connect each device as shown in the figure, that is: connect the pH electrode to the BNC interface of the pH meter circuit board, and then use an analog connection line to connect the pH meter circuit board to the analog port 2 of the Arduino master controller. After powering the Arduino master controller, you can see that the blue indicator light on the pH meter circuit board turns on.
(2) Program the sample code for the Arduino master controller.
(3) Insert the pH electrode into the standard solution with a pH value of 7.00, or directly short-circuit the two inputs of the BNC interface, open the serial monitor of the Arduino IDE, and you can see the currently printed pH value, and the error will not exceed 0.3. Record the value printed at this time, and then compare it with 7.00 and modify the difference to the Offset in the program (difference = standard value (7.0) - printed value). For example, if the printed pH value is 6.88, then the difference is 0.12, then change #define Offset 0.00 to #define Offset 0.12 in the sample program.
(4) Insert the pH electrode into the calibration solution with a pH value of 4.00. After waiting for one minute, adjust the gain potentiometer to make the printed pH value as stable as possible around 4.00. At this point, the acid section calibration has been completed and you can test the pH value of the acidic solution. Note: When measuring other solutions, the electrode must be cleaned.
(5) Relying on the linear characteristics of the pH electrode itself, after the above calibration, the pH value of the alkaline solution can be directly measured, but if you want to obtain better accuracy, it is recommended to recalibrate. The alkaline section is calibrated using a standard solution with a pH value of 9.18, and the gain potentiometer is also adjusted to stabilize it at around 9.18. After calibration, you are now ready to measure the pH of alkaline solutions.
Result：
Open the serial port monitor, adjust the baud rate to 9600, and read the pH value of the water source measured by the pH meter in the serial port.
Maintenance and precautions：
When the electrode is used for the first time or will not be used again after being left for a long time, soak the electrode bulb and sand core in 3NKCL solution for 8 hours to activate.
After removing the electrode protective cover, be careful that the sensitive glass bubble inside the plastic protective grid does not come into contact with hard objects. Any damage or scratches will cause the electrode to fail.
After the measurement is completed, the electrode protective cover should be put on when not in use. A small amount of 3.3mol/L potassium chloride solution should be placed in the protective cover to keep the electrode bulb moist.
The terminals of the electrodes must be kept clean and dry, and short circuiting at both ends of the outputs must be avoided, otherwise the measurement results will be inaccurate or invalid.
Avoid immersing the electrode in distilled water or protein solution or acidic chloride solution for a long time, and avoid contact with silicone grease.
After the electrode has been used for a long time, if the gradient is found to be slightly reduced, the lower end of the electrode can be soaked in 4% HF (hydrofluoric acid) for 3-5 seconds, washed with distilled water, and then soaked in potassium chloride solution. It's new again.
If the measured solution contains substances that can easily contaminate the sensitive bulb or block the liquid junction, thereby passivating the electrode, the phenomenon will be a decrease in the sensitivity gradient and inaccurate readings. In this case, it should be cleaned with an appropriate solution according to the nature of the pollutant to make it new again.
When choosing a cleaning agent, such as a cleaning fluid that can dissolve polycarbonate resin, such as carbon tetrachloride, trichlorethylene, tetrahydrofuran, etc., the polycarbonate resin may be dissolved and applied to the sensitive glass bulb, causing the electrode to fail. Please use it with caution!
Module 3: Feedback adjustment
By using the GJ40DA model solid-state relay and the REX-C100 model PID thermostat, we have implemented a system that can automatically regulate the temperature with a light bulb or heater. With the help of the core development board, we control the output intensity of multiple connected light bulbs to adjust the light in the culture environment, and also carry a timer module to set the output of culture parameters.
Finally, our shell will select appropriate materials according to the project function to meet the antibacterial and temperature control requirements under the function.
Temperature control module
Description of working principle
a. The thermostat outputs DC voltage to the solid-state relay. Through this voltage, the voltage at the output terminal of the solid-state relay is adjusted to control the heating power of the electric heating tube.
b. The thermostat outputs a DC voltage signal to the solid-state relay. After the DC voltage is present, the output terminal of the solid-state relay passes through and the electric heating tube works. If there is no voltage, the output terminal will be disconnected. The electric heating tube will not work when the power is turned off. It only controls the on and off of the electric heating tube.
Light module
Circuit connection
a. The light sensor VCC and GND are connected to the 5V and GND of the board;
b. Select the analog signal output port AO (analog output) of the light sensor and connect it to A0 (analog in) of Arduino;
c. Select Arduino’s digital pin 6 (digital PWM) to connect the positive electrode of the light-emitting diode, and GND to the negative electrode; you can connect multiple LEDs in series, or add a 1k resistor;
Timer module
Function settings:
Press K1 for the first time. It takes more than 1 second to be effective, to prevent false triggering. Display: P-11: K2 adjusts the main mode, K3K4 adjusts the function. Press K1 for the second time, the screen displays: AO01: K2 and K3 adjust the first time A, K4 adjusts the decimal point (time unit) by pressing K1 for the third time, the screen displays: BO01: K2 and K3 adjust the second time B, K4 adjusts the decimal point (time unit) by pressing K1 for the fourth time, the screen displays "——--" Indicates entering standby state
Press K4 in standby mode to permanently turn off/on the display and switch to low-power mode
Decimal point time unit description:
x.XX The decimal point is in the hundreds place, and the timing range is: 0.01 seconds to 9.99 seconds. XX.X The decimal point is in the tens place. The timing range is: 0.1 seconds to 99.9 seconds. bit, timing range: 1 minute to 999 minutes
Module 4: Automation and Interaction
Automation control
The multi-functional automatic microbial culture machine can make the growth process of microorganisms more intelligent and efficient through automated control. Specifically include
① Temperature control: Automatic temperature control can be performed according to different culture needs to ensure that the temperature of the culture environment is stable and the temperature range is adjustable.
② Humidity control: It has the function of controlling humidity and can automatically adjust according to different culture needs to maintain appropriate humidity. (Default)
③ Gas control: Automatic control of the culture environment atmosphere can be achieved by controlling the air inlet and outlet volume, oxygen content, etc.
④ Time control: Automatic control of culture time can be realized to ensure that the culture process can be accurately controlled and monitored.
⑤ Liquid level control: It can realize automatic control of culture liquid level and ensure adequate supply of culture liquid. (Default)
⑥ Lighting control: By controlling the number, intensity, etc. of light sources, automatic control of the lighting in the culture environment is achieved.
⑦ Quantity control: Control the quantity of the culture material through real-time detection of weight, etc.
⑧ PH control: Control the pH of cultured substances through pH detection and buffer adjustment.
We will introduce an intelligent AI system as the processing control center of the software system to perform real-time intelligent processing and realize automatic control without direct human operation, so as to achieve the purpose of efficient and portable cultivation of microorganisms.
Intelligent interaction
The multi-functional automatic microbial culture machine can be connected through the intelligent cloud to achieve interconnection with users' mobile phones, computers and other devices, allowing users to manage and interact anytime and anywhere.
In order to give full play to the functions of hardware products, we have developed a hardware and software system that focuses on information transmission control. With the function of the ESP-01S module, we are able to run the software system on the mobile phone and control it through arduino with the help of the cloud platform. Each module to be connected (for details, please click
Shortcomings and improvements:
Our ideal expected effect actually includes the atmosphere detection module, image acquisition module, and the automation and interactive functions have reached maturity. However, due to the influence of many factors, we are not yet able to realize the above functions or the related functions are immature. But in the future, for the purpose of learning for excellence, we will plan to implement the above shortcomings and add control systems such as humidity and liquid level, and match them with appropriate image acquisition modules and implement automation, etc., so as to make the product more complete and truly suitable for use. the needs of the users.
Hardware housing design
After the basic function of each module of the hardware product runs, we begin to design the shell of the product. In order to maximize the function of our products in the design, we combine the target population, product function, market demand and other factors. The following is the detailed process of our design.
Target users and markets
Combined with the functional analysis of the product, we positioned the target users as consumer groups of academic scientific research or microbial companies, including those who love microorganisms but cannot provide sufficient management time for microorganisms due to busy work arrangements, and those young groups who are full of pursuit of environmental protection, health and scientific sense.
After the initial determination of the target user, we need to consider the preferences of customers in the appearance design of the product. It is estimated that our main customers are between 20 and 35 years old, so we should try our best to be concise and beautiful in the appearance design, and avoid fancy and complicated patterns; The selection of shell materials should be as light and durable as possible.
Market research on similar products
After determining the main customer group, we conducted a survey of similar products in the market. This research is mainly for shell material. We sorted out the market with similar functions, and got some inspiration from it.
Enlightening point:
• Can be found in similar products: most of the inner liners use copper or stainless steel materials, such materials have a good antibacterial effect and are easy to clean, at the same time, affordable. The outer gallbladder is generally cold-rolled steel plate and sprayed with a special coating on the surface
• In some products, it is also found that in order to achieve the effect of heat insulation of the device, the insulation layer will be increased, generally filled with polyurethane.
• This team made a small automatic culture machine. The shell is initially intended to use 3D printing, so the printing material needs further consultation. The inner liner can be made of copper or stainless steel.
Search for available shell materials
After the target customer presupposition and market research, we initially identified two main requirements for the shell material - ① the inner material is easy to clean, the surface is smooth, and the bacteria is difficult to propagate on its surface. ② The outer material will not cause damage to human skin, and has a thermal insulation effect.
Then we search for available materials according to relevant literature and materials, and the available materials initially screened are as follows.
Make the shell model
Preliminary discussion of shell model
After completing the preliminary investigation work, we began to build the shell appearance model.
Through nearly two hours of online meeting, my partner and I made preliminary determination of the size of the shell and the specific internal support according to the size and placement of each functional module, and drew a sketch. During the discussion, we encountered a number of problems, but fortunately we found solutions in the end.
The first is that our ability is limited, we can not add insulation materials between the inner and outer layers to achieve the effect of inner and outer adhesion, our solution is to choose the shell material with better insulation effect, and install the inner shell material separately. However, it is not easy to install it separately to ensure the sealing effect of the inner shell, so we came up with a solution to install it in blocks. Internal grooves on the back and two sides of the shell are designed to clamp the side steel plate of the inner shell, while small support tables are designed inside the shell to support the bottom of the inner shell, so as to leave a certain gap between the inner shell and maximize the effect of tight connection of the inner shell. The detailed discussion sketch is below.
Use ug to draw a concrete model look
Referring to the preliminary sketch design, we use ug to draw a specific model and standardize the size, which is convenient for the subsequent printing of the shell. The specific diagram is shown in the following figure.
Product appearance rendering
In order to achieve better publicity effects for the team's products, we made product renderings to visually present the actual product expectations in front of customers, so that customers can better understand our products. The render effect is shown in the image below.
Make realistic housing
After doing all the preparatory work, we began to look for a machine that could complete the shell printing. Unfortunately, after contacting the school tutor, we learned that due to the large size of our shell, the existing 3D printer in the school did not support printing our shell. After the teacher suggested that we use the method of plate cutting and splicing to make the shell, after listening to the teacher's suggestion, we immediately contacted the relevant factory online, using acrylic material to make the shell, and the inner shell was made by looking for factories to cut stainless steel plate offline.
Although it is not possible to use the expected material for the production of the shell, acrylic material is also an important plastic polymer material developed earlier, with good transparency, chemical stability and weather resistance, easy dyeing, easy processing, beautiful appearance, and has a wide range of applications in the construction industry.
Final assembly of hardware products
After the acrylic shell is made, we begin the final part assembly. Assemble the shell with the inner shell and the internal parts into one, and check the realization of the function.
Result
After ensuring that the functions of each major module are realized, we provide sufficient power, grounding, and information transmission interfaces with the help of breadboard expansion jacks to ensure synchronous integration of the integrated modules. In this process, we need to consider the module placement, wiring layout and other factors for the design of the product shell, in order to efficiently use space, to achieve the characteristics of simple and lightweight products.
In addition, because our temperature control, sterilization, iot modules need to take into account the fit of the power supply size, the use of high efficiency, professional requirements for functional implementation and other factors, will be relatively independent installation in other locations of the product space.
The installation of finished products is shown in the following figure.
Future Prospects
About part quality
In the hardware products designed this time, due to the consideration of team funds and the initial production, the components we purchased are almost biased to the low price and the function is relatively satisfying the demand. Therefore, to a certain extent, the hardware products with full functions and high quality in our concept can not be well played. Therefore, in the future design work, we will continue to look for more compliant, functional and quality components for iterative replacement, so that our hardware products are more in line with the high standards of the market and meet the human needs of multi-group use.
About housing materials
Due to insufficient conditions, we were not able to use 3D printing to make the shell as expected, so the insulation capacity of the shell was also reduced. In the future, we will further update the hardware shell, look for the actual data comparing a variety of materials, and finally choose a material with better insulation and higher safety to replace it. At the same time, we will also consider filling the insulation material between the shell and the inner shell to achieve higher performance of the incubator.
In short, we will continue to upgrade our product and make it more functional and able to play a role in the field of synthetic biology.