Team:LINKS China/Hardware
Inspiration
In the process of our leather production, our team faced a thorny problem: During cultivation of our leather, we always face the situation that the leather was contaminated by airborne microorganisms, such as fungi and mould. To obtain some inspirations in dealing with this severe problem, we visited the Classy Kiss yogurt factory located in Baoan District, Shenzhen. (Click here to visit our human practices page for details) The factory contained a thoroughly dust-free plant for the fermentation of milk. Inside they got fully sealed and sterilized fermentation tank. This sterilization was accomplished by filtration of air entering the workshop, creating a positive pressure environment, and several steps of cleaning procedure before and after the fermentation.
After this visit, we decided to create a bacteria-free environment for our leather cultivation to largely eliminate the possibility of contamination from the outer environment with, most importantly, sterilization and a suitable temperature. There were two stages of designs for our leather cultivation, resulting in two machines. We named them the PaleoLeathic Tanner and the Neoleathic Tanner.
The PaleoLeathic Tanner: A Remolded Oven for Cultivation
Version 1.0
After the visit, we comprehended our inspirations and fulfilled the production requirements in our first hardware design. To get started, we brought an oven from the market and dissect it for re-installation, created a cultivation box called the PaleoLeathic Tanner, the first NeoLeather producer. Several parts of the oven was being remolded for improvement to reach our cultivation requirements:
Bacteria-free Environment and Sterilization
The complete sterilization of the environment using massive filtration machines is ideal but not practical. An attainable solution is the sealing of box openings using medical PE films and industrial water-proof tapes, with UV lights installation for the disinfection of the internal space before and after leather production. The usage of medical films ensures a bacteria-free leather production as well as a promising chance for gas exchange to provide an adequate supply of oxygen during cultivation.
Suitable Temperature
We utilized a temperature control board with a thermal detection probe, along with a heating plate to maintain a stable and suitable temperature set for the leather production in our design automatically.
Inner Gas Circulation
We used a small and low power fan for gas circulation, making the inner temperature more even and promoting gas exchange at the site of medical membrane.
Sample Loading
Because of the internal sterilization of the PaleoLeathic Tanner before cultivation, we were unable to load bacterial samples into the cultivation medium in advance. To solve this problem, we placed a retention needle across the original vent hole of the PaleoLeathic Tanner and connected the interior with the exterior. With the needle hanging above the culture tank, we enabled a bacteria-free sample loading after the internal box had been completely sterilized. In addition, we sealed the placing position of the retention needle using multilayered medical PE film to both block bacterial contaminations and allow gas to enter and exit the PaleoLeathic Tanner.
Culture of Leather and User Feedbacks
After the retrofitting of the drying oven was complete, we cultured a leather using our Version 1.0 Box, and our team’s PI, Wang Boxiang summarized the user feedbacks collected: “The overall experience of the first fermentation was very good. The sterilization was in place, and the adding of samples was convenient; no mold contamination was found on our cultivated membrane, and the growth of our microorganisms and BC membrane was rapid. However, the sealing of the box was not proper, allowing the growth of some fruit flies at the end of the cultivation. My recommendations are: 1. to be more careful in the sealing and waterproofing of the box. 2. to include a white light and a larger window for a more unambiguous observation of the process of the fermentation and the timely making of adjustments. 3. to use multi-layer fermentation to more efficiently use space inside of the box.”
At the beginning and the middle of the first fermentation, the sealing was intact and no fruit flies were discovered. However, towards the end of the fermentation, when our bacterial cellulose membrane was shaped, we found the presence of fruit flies. We discovered the cause of the growth of fruit flies: the PaleoLeathic Tanner was unable to drain the water in the cultivation liquid at the end of the fermentation, causing the medical sealing tape to get soaked and therefore opened. The fruit flies then flew in and lay eggs.
We resolved this problem by replacing the original tape with a new fireproof and thermal resistant sealing glue in version 2.0. In addition, we made several changes in response of the user feedbacks:
Version 2.0
Sealing of the PaleoLeathic Tanner
We solved the problem of contamination due to the soaking of the medical sealing tape by replacing it with a better and safer food grade glass glue.
Removing the water vapor in the air during cultivation
During the process of cultivation, water vapor condensed and gathered to the bottom of the PaleoLeathic Tanner Version 1.0, causing the rusting of the PaleoLeathic Tanner and soaking of glue. The occurrence of these situations leads to high probabilities of future contaminations that place a negative effect to our cultivations. Therefore, we added Calcium Chloride dehumidification agents to the PaleoLeathic Tanner for water adsorption, reducing the amassment of water within the box. Furthermore, we sprayed every metal component located at the bottom of the box with anti-rust spray paint to reduce the probability of future rusting of the box and increase the service life of the PaleoLeathic Tanner.
Multiple Layer Cultivation
According to our user feedback, one-layered cultivation is far from satisfying future mass productions of our leather. Thence, we added another layer to the PaleoLeathic Tanner Version 2.0, which simultaneously increased the requirements on loading of samples. To meet these requirements, we added 2 long infusion tubes for contemporary usage with the retention needle. Before cultivation, each infusion tube is fixated onto the culture tanks for direct and accordingly adding of samples.
Addition of LED
In response to the user feedback, we added a high brightness LED white light for an easier observation of the growth of the BC membrane through the glass on the box door.
How to Use: the PaleoLeathic Tanner
Despite of the complicated functions of our box, the PaleoLeathic Tanner is easy to operate. The steps of culturing operations are described below.
- Turn on the fan
- Turn on the UV light for disinfection for over 30 minutes
- Put the sterilized culture medium into the box
- Disinfect the culture medium with the UV light for over 30 minutes
- Close the UV light after oven 30 minutes
- Insert the cultivation liquid and the bacteria sample into the culture medium and wait for static culture
The NeoLeathic Tanner: An Automated Designed Box for NeoLeather Production
To reduce the relatively large manpower consumption of traditional leather cultivation, we hoped to create a fully automated leather production process: cultivating, washing, and drying. Hence, we designed a completely new box that will be able to both culture the leather, drain water from the box in the end of the cultivation, and wash the leather after culture with reference to the previous box. This was the prototype of our fully automated machine: the NeoLeathic Tanner, the leather producer in the NeoLeathic Age:
Observations
In response of the user feedbacks from the Version 1.0 PaleoLeathic Tanner, we included a larger glass window in our new design for the easier observations of the process of the leather production and making quicker adjustments. We also added a few LED lights for a clearer observation as we did in the PaleoLeathic Tanner.
Sterilization
We increased the number of UV light tubes to 2 with one on the top and one on the bottom to better enhance a bacteria-free environment in all areas inside of the NeoLeathic Tanner.
Adding Liquids
The adding of cultivation liquid without contamination is required for the production of our leather. To achieve a completely bacteria-free environment while adding liquids automatically, we utilized two peristaltic pumps. The peristaltic pumps ensures a bacteria- free suction of liquid into the box since it requires no contact between the liquid and the inner structure of the pump when it is working.
Loading Samples
An infusion tube along with a retention needle were used to add bacteria samples into the culture medium. The retention needle was utilized, with the head being left outside of the box, and the connected infusion tube was placed above the culture medium inside of the box to add bacterial samples easily through an injection syringe with needle.
Washing the Leather
Taking into consideration of the fact that a sterilized environment is not necessary when washing the leather after culture, we decided to use 2 electromagnetic valves, valves that does not provide a completely bacteria-free environment like the peristaltic pump. One of the valves is used for controlling the discharging of water into the Tanner using the natural pressure of the water. The other valve is used for controlling the release of water after each round of cultivation or washing of NeoLeather when needed for the preceding of the steps of production of the leather.
Working Procedure of the Neoleathic Tanner
The Future of the NeoLeathic Tanner
Combining suggestions, users feedbacks and what we found to be deficient during construction and testing the NeoLeathic Tanner, we made several points in the following for improvement in the future.
- Due to time limitations, the NeoLeathic Tanner did not achieve the level of full automation. In the future, we will design a circuit board and program it to control all components of the Tanner to finish periodic cultivation processes.
- The design of the door shaft of the Tanner’s door needs adjustment. We will adjust the position of the door shaft to be closer to the door edge to enhance better opening and closing of the door, therefore for better sealing condition.
- There were no vent holes enabling gas exchange inside of the Tanner. Throughout the communication between our instructor, Stephen Ye, and BNDS_China’s instructor Tingzhen Liu, we got several users feedbacks and suggestions. For gas exchange, we will probably make openings on the Tanner and cover them with HEPA filters, which perform well in filtering out microorganisms in the air. Then, we will use fans to blow air into and out of the Tanner to enable gas exchange and blow out excess water vapor. Furthermore, for the addition of samples, we could discard several joints for connection of tubes and pumps, and use a medical Three-way Stopcock and extension tubes instead. This may largely save the time we use to clean each injection port and decrease contamination possibility at the same time.
- We will add a layer of protective metal net on the heating plate to prevent any accidents such as falling of foreign bodies, burns and short circuits.
- It is very hard to lock the door. We will probably reduce the thickness of the door or adjust the Tanner to have the same height as the door for an easily working lock along with better sealing of the Tanner.
- We will probably use the method of magnetic attraction to more conveniently control the opening and closing of the door.
Building a Neoleathic Tanner
The Neoleathich Tanner consists two major parts: the metal tanner and other component appliances. You could find a detailed description of the Neoleathic Tanner in this section: How to Build Your Neoleathic Tanner?
Notice About the Neoleathic Tanner Software for Automation
After we effectuated designing the machine and manufactured it in reality, we found that there is no time for us to design a software for it while setting up the Neoleathic Tanner and testing it. We aim to build an automatic machine for all procedure of making an artificial leather, and we will accomplish that goal in the future, by both applying a central controlling broad and an complete software for the procedure.
How to Build Your Own Neoleathic Tanner?
Technical Component and Construction Instruction
If you want to create your own Neoleathic Tanner, you may first take a look at the table of Constructive Parts on the machine. For the whole model design of the box, you can access to it from the link below.
Download the latest Fusion 360 model from this link here: Download
If you cannot open the link above to get the latest design, you may download this version (version 80), which is the latest version at the time we uploaded the file to this wiki page.
(Suggestion from the reality: The Outer Body might use thickness 1.5mm Stainless Metal Plate and the other parts might use 1.0~1.25mm, or the whole box might be too heavy.)
After building our tanner, we found there are lots of spots that we have to improve and redesign more wisely. If there is any update on the design in the future, the link of Fusion 360 will automatically show the latest design while you access it.
While we were building the Neoleathic Tanner, some materials that we used were not included in the list because we assumed that they were basic and already available, such as 1.25mm wire, switches, and insulated tapes.
Also, some of the parts that on the box has been included in the tanner, and therefore were not included in the table as well. We made all of those parts in a factory together with our outer box based on our Fusion 360 model.
Circuit Diagram (Layout Design)
Construction Instruction
All component could either be fixed by screws or glue. Please construct the tanner according to the Fusion 360 designed model, which can be accessed at the beginning of this section. It has all the spots and specifications of screws were used. For the wiring connection of different appliances, please relate to the circuit diagram in the next section.
