Contact lens care solution with DMBT1 protein can prevent users from contracting Pseudomonas aeruginosa, but DMBT1 protein is after all a consumable product, and it is not possible to observe when the solution will fail when the user is using this specially formulated care solution. Most of the smart contact lens cases currently on the market only have a simple acoustic wave cleaning function. Since the sound waves of these cases do not reach the frequency of ultrasonic waves, they are unable to clean on a biological level and can only clean on a physical level to a certain extent. In order to be able to further ensure the safety of users and better match our proposed specialty care solution, we designed, built, tested and open-sourced OptiCare LensCase, a multi-functional smart contact lens case based on a single-chip microcontroller.OptiCare LensCase monitors the physicochemical composition of the care solution (pH, TDS) in real time, and can be OptiCare LensCase can monitor the physicochemical composition (pH, TDS) of the care solution in real time and upload it to a cloud server in real time, has a user-friendly touch-screen interactive interface, and an ultraviolet disinfection module for emergency situations.
The main components of the OptiCare LensCase include a UV lamp disinfection module, a 2.4-inch touchable interactive serial screen, an ESP32-WROOM, an 18650 battery module, a pH sensor module, a temperature sensor module, a TDS sensor module, and a light-curing print enclosure.The ESP32-WROOM, with its three sensor modules, monitors the real-time condition of the care solution's components and draws a function image with time as the independent variable, which is displayed on the 2.4-inch serial screen. At the same time, it controls the UV lamp disinfection module, which allows the user to control the UV lamp on/off by manipulating the screen. All power supply is done by the 18650 battery module. This module is powered by a total of two 18650 batteries.
In fact, we did a total of three rounds of hardware experiments. In the first round of hardware experiments, we originally did not have the idea of IoT systems, so we chose the stm32 series microcontroller, using a stm32F103c8t6 development board, and added a FZ60 expansion board to power.
And initially, we chose to use a sensor that, in addition to pH, temperature, and TDS, also has an ORP (Oxidation Reduction Potential) sensor. For the numerical display, we chose a 0.96" OLED screen.
However, we soon found problems - the overall size of the electronic core components is too large, the ORP and pH sensors are especially large; the OLED screen is too small and can only display 3 values in real time, which does not have a cumulative effect on time and has little reference value. Based on these problems, we quickly launched a second round of experiments - we chose to add the ESP8266 as a networking communication module on the basis of the original circuit, and replaced the original OLED screen with a 3.5-inch serial capacitive screen. At the same time, we chose to delete the ORP sensor, considering that the ORP value would not change much for both common general and non-general conditions for contact lens care solution.
However, the results of the second round of hardware experiments are still unsatisfactory - the communication between the stm32c8t6 and the ESP8266 is not as smooth as we expected, both of which are essentially MCUs, but with a large performance gap and a large clock frequency difference. In order to be able to accurately receive packets, we had to use the idea of handshake protocols to barely ensure that the data of the two can be sent and received correctly, but this will undoubtedly waste a lot of computational resources, as well as wasting more physical space. On the other hand, we are also reflecting on the fact that what we are currently working on can only serve the function of alerting the user, which seems to be somewhat lacking in functionality. We wanted the hardware to be able to "clean" after detecting contamination. Our first thought was to use an ultrasonic module. However, this option was quickly rejected by us. The reason was that the ultrasonic oscillator was too large, could only work properly with 220v, and consumed too much power for the battery. Therefore, we could not design it as a portable electronic product. Therefore, we came up with the idea of using UV light instead of ultrasound for sterilization at the biological level. Based on the above ideas, we started the third round of hardware experiments and achieved a more satisfactory result in the end.
In order to be able to realize the idea of IoT, we chose the ESP series of microcontrollers as the main controller. After considering the size, power consumption and cost, we finally chose ESP-WROOM-32.
There are a total of 3 sensors that we are going to access, the PH sensor, the temperature sensor, and the TDS sensor.
In this case, the DS18B20 temperature sensor is used as a soft compensation accessory for the PH and TDS sensors. We use the ADC of the ESP-WROOM-32 to convert analog data to digital data. the ESP-WROOM-32 can only provide 3.3v outward, which means we must need an additional voltage source, because all three sensors need 5.0v, and the closer the voltage is to 5.0v, the more accurate the data is.
Regarding the UV disinfection module, we need to consider several issues: operating voltage, operating current, operating power, UV spectrum. One of the best solution is the UV spectrum, according to the ready-made module, we choose the UV lamp with 255nm wavelength which has the best relative disinfection effect. Regarding the operating current and power, considering the fact that the area we need to irradiate with UV is not very large, so fortunately we don't need too high power UV lamps, which means that there will not be a very huge amount of heat production, we finally welded the UV lamps to a 20mm diameter aluminum plate to ensure that it dissipates heat properly. However, the operating voltage was a headache. Considering the safety issue, we didn't want our device to have too high a voltage or too much current, and all the modules except the UV lamps followed this principle. After a long period of research and consultation, we found a UV lamp with an operating voltage of 8v, and with the assistance of our staff and teachers, we re-soldered a new resistor on it, to the point that it can operate at 7.4v with a guaranteed power rating.
Nowadays, the intelligence of various electronic products is more and more popular, and the interaction with electronic products is also more and more humanized. Considering user-oriented issues, we believe that the design of a "humanized" screen is still very necessary. In order to match the microcontroller, match the corresponding voltage, but also match the size of our expected target products, we finally chose the 3.5-inch serial screen, and choose the same type of capacitive screen with mainstream cell phones to achieve touch interaction, so that the user gets our products in a very short period of time after the hand can get used to it.
As for the display on the screen, we believe that the parameters obtained by the sensor are more informative about the cumulative values over time, so we chose to show the curves of pH, temperature, and TDS over time, and to monitor these values at any time, classifying them in four levels: "normal", "moderate", "more severe", and "severe", and displaying them on the screen. Therefore, we chose to display the pH, temperature and TDS curves over time and monitor these values at all times, classifying them in four levels: "normal", "moderate", "more serious" and "serious", and displaying them on the screen. At the same time, we also display the UV lamp on/off switch on the screen. When the level rises to the severe level, the device will automatically turn on the UV lamp module for a continuous 40-minute disinfection operation.
Combining the previously mentioned devices, we concluded that the voltages we need to provide include 3.3v, 5.0v, and 7.4v. Since we want to try to package the final product as common as possible for users, we choose the more common 18650 battery as the power source and use two series-connected batteries to provide higher voltages externally. We set up this module to provide all three of these voltages directly to the outside world, so all we need to do is connect all the pins that need to be powered by the device directly to the battery module. One of this battery module uses rechargeable 18650 batteries, and according to the manufacturer's description, the module supports fast charging mode, using the type-C port for fast charging.
For both pH and TDS values, common bacterial colonization, including particulate matter such as dust of common diameters, can cause a sudden increase in both values in a short period of time if it enters the care solution; similarly, the depletion of DMBT1 proteins can cause a slow decrease in the TDS value of the care solution. Based on this principle, we implement the sensor monitoring module. We first tested a standard care solution (clean care solution with the optimal concentration of DMBT1 protein) several times at room temperature and took its average value, which resulted in a pH value of 7.36 and a TDS value of 9324. Similarly, we also tested a care solution that had consumed a certain level of DMBT1 protein (theoretically not having a good bacteriostatic effect) several times at room temperature, which gave us the following results. The pH value is almost the same as the baseline value, and the TDS value is about 300 different from the baseline value. Therefore, regarding the TDS value, we divided three levels within the range of 300 downwards, centered on the benchmark value, which are "normal", "medium" and "more serious". For the rising situation, we also give a buffer area of 150, if the downward exceeds 300 or upward exceeds 150, it is regarded as a "serious" situation, the microcontroller will automatically turn on the UV lamp disinfection module, and remind the user to replace the new care solution in a timely manner. For pH value, according to the national standard, when the pH exceeds the range of 6.5~7.8, it is regarded as unqualified care solution, which also warns the user to replace the care solution with a new one, but does not activate the UV disinfection module.
Nowadays, the Internet of Everything has become a development trend of electronic products. In our research on contact lens users, we learned that contact lens cases are not as important to carry around as normal eyeglass cases, and most people choose to place their contact lens cases in the washroom or on the nightstand for a long period of time. Therefore, when we designed the OptiCare LensCase, we also considered adding the Iot function module, which is one of the reasons why we chose the ESP series microcontroller.
We utilize the Iot platform to enable real-time monitoring of ESP32 data, which can be used as a back-end data monitoring of the product in the hands of all users by staff and technicians. In the future, assuming that OptiCare LensCase has sold a very large number of units, we can even analyze the user's habit of using contact lenses based on the data of most users, and after discussion and analysis by experts, we can make more professional suggestions to users as a way to further protect their eye health.
In addition to the interface for technicians, we have also designed a simple "humanized" web page for users, which allows them to bind multiple Smart Glasses cases (although this is not usually necessary), to see the pH and TDS values over a period of 12 hours, and to directly see the evaluation of the current quality of the care solution, as well as the temperature display. Evaluation, as well as temperature display. We have also created a "contamination rate" interface that combines the percentage of real-time values with the range values.
Since we haven't seen any products on the market that meet our design ideas yet, we have plenty of freedom to play around with the design of the case. Since the contact lens case we are going to design has the characteristics of small size and complex internal structure, we choose 3D modeling and then use light curing printing to obtain the shell.
In terms of case design, we tried to minimize the overall size of the glasses case, one of the inevitable points is the size of the pH sensor, which has an internal electrode like a pen, so it enlarges the length of our product to a great extent. Since we needed to keep the ends of all 3 sensors fully immersed in the care solution, we first designed a small compartment to hold the care solution and contact lenses, and then made a little groove down the edge of this compartment to allow the care solution to flow smoothly into a small compartment on the lower level. Since all the electronic components are centrally located on the lower level, we extended the ends of the 3 sensors into this lower compartment and encapsulated the edges of the sensors with waterproof gaskets and waterproof adhesive.
We completed the model design using CATIA V5R20 software and printed the model on a light-curing 3D printer in our lab.
In order to be able to carry and design easily, we soldered all the development boards on a double-sided hole board and drew the corresponding circuit diagrams.
According to this circuit diagram, we manually carried out the soldering, of which it should be noted that we utilized an 8550 transistor to create the switching circuit of the UV lamp module, in which about 900Ω or so chip resistor was used as the pull-up resistor and fixed on the back of the hole board with hot melt glue. Finally, under the guidance of our teacher, we finished soldering this core board.
After the assembly was completed, a set of experiments was conducted to simulate the effects of actual use. First, we added a normal amount of care solution containing a certain concentration of DMBT1 protein, and then purchased a new pair of contact lenses to put into it. We simulated the osmotic pressure of the human eye and made a cup of solution that represented the environment of the human eye. During the day, the contact lenses were placed in the solution, placed in a beaker, and placed in an open-air environment to simulate what happens when a person wears them during the day (at this point, the case is placed in the lab normally, with the lid closed, to keep it running low-power); and at night, the contact lenses were placed in our contact lens case to simulate what happens when a person removes their contact lenses and goes to bed at night. Specifically, we defined daytime as 7:00 - 23:00, and nighttime as 23:00 - 7:00 the next morning. Normal conditions were tested for 3 consecutive days. We simulated that on the 4th night before going to bed, the user directly touched the contact lens lens with unclean hands, and the following are the curves of pH and TDS data we observed over time.
Combining power consumption and safety issues, we set the ESP32 to read data every 30 seconds. We observed that since the pH sensor and TDS sensor we used were not up to industrial grade standards, they may not have reached a very high standard in terms of accuracy and stability, but as far as the data we obtained is concerned, the data range has reached our expected standard. Therefore, in terms of acquiring data from the sensors, although there is still some room for improvement, I believe we have done the best we can.
After finishing the design, splicing and assembling, in order to make sure that our product can gain the support of a wide range of users and can really be put into the market, we briefly organized an event on campus, asking 30 contact lens wearers to experience our product on site and fill out the questionnaire on the spot. In the end, we got 30 feedbacks and suggestions. Luckily, we received positive feedback from most of the students.17 were very interested in our product interaction, and 3 thought that we should continue to reduce the size of the product and try to make it as small as a common Bluetooth headset case.
Since we are oriented to the undergraduate production level, there is still a lot of room for theoretical improvement of our products. For example, if we want to develop for enterprise, we can design our own PCB circuit, which can greatly reduce the volume and power consumption of the hardware, and greatly improve its degree of regularity. We can do more research for the community at large, to get more accurate and more valuable feedback, so as to correctly evaluate our design program. With more cost, we can also try to use more advanced sensors to get more accurate values, we can try to change the shape of the sensor electrodes to fit the size of the housing, and we can use lithium batteries instead of 18650 batteries, which will further reduce the size of the product.
At the same time, for a larger user group, because we do the Internet of Things system, when the collection of the most adequate amount of user data, we can also use big data analysis, training a classification model or evaluation model, for each individual user can give more specific habit correction suggestions, in order to further improve the experience of our products.
In order to be able to accommodate the batch production of DMBT1 protein by our designed engineered bacteria, we considered designing a customized bioreaction vessel. Since our designed E. coli uses temperature to control the production of DMBT1 protein, our bioreaction vessel should have a temperature control system as the main part. On top of that, taking the idea of our hardware from board 1, we should also include pH, temperature, TDS, and ORP sensors for numerical monitoring. Since the bioreaction vessel requires high accuracy of temperature, we can use water bath heating for temperature control.
We arrange the sensors on the lid of the container. During the normal reaction, the end of these sensors can be fully extended into the reaction solution, to ensure real-time monitoring of the relevant values in the center of the solution. At the same time, we also arrange UV disinfection lamps on the reaction lid, so that when an experiment fails, it can also be terminated in an emergency by using the UV disinfection lamps, which largely reduces the requirements for the use of biological reaction containers, and facilitates the training of staff in batch.
We have centralized all the controls and displays on the display screen in the base, which is easy for the staff to manipulate. For normal conditions, E. coli can be maintained at a relatively fixed concentration for a long time, keeping the reaction in the container. Therefore, we need to have an outlet for waste liquid and an inlet for culture liquid. We designed the inlet port on the lid and the waste liquid outlet on the bottle.
For long term factory projects, we can have further automation for the inlet and outlet, by using sensors to detect the values and automatically determine whether the current nutrient solution needs to be replaced with a new one or not. However, due to the complexity of the purification process, this part still needs to be done manually. However, our device can automate the long-term culture process, i.e., the staff no longer need to spend a long time dealing with the culture and production of E. coli.
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