Hardware | SJTU-BioX-Shanghai

Our final product is designed to work in natural flowing water bodies, which requires a hardware that can carry the engineered bacteria and work in outdoor environments. This is a challenging and innovative requirement, compared to most wastewater treatment projects that take place in mild sewage treatment tanks.

In the hardware design, we need to consider 3 functional areas:

     1.Culture area (A area):Area used for the growth and propagation of engineered bacteria, resulting in the production of OMVs.
     2.Combination area (B area): OMVs capture and bind heavy metal ions.
     3.Collection area (C area): Nickel nets are used to capture and enrich OMVs by interacting with His-tags on OMVs.

To meet the requirement of continuous operation in wild environments, all modules containing motors will be powered by solar panels. We only need to periodically clean and replace the Nickel nets that has captured a large amount of OMVs (already with bound heavy metal ions), and periodically add feed packages (containing engineered bacterial strains and dry medium). In this way, our product can work effectively in wild environments for a long time.

This is our first version of hardware design. Although it was eventually overturned and redesigned due to certain reasons, it still has many interesting design features that worth showcasing.

Initially, Yang Zhenxi proposed an intriguing biomimetic design concept inspired by orange: imprisoning engineered bacteria within citrus segments and encapsulating them with bacterial membranes to prevent leakage. Nutrient medium is supplied through the central tube, simulating a real citrus fruit. The citrus segments rotate continuously, interacting with the flowing water and release OMV (Outer Membrane Vesicles).

To further optimize this idea, we drew inspiration from industrial water filters and bioengineering purification units to design the first version of our hardware. In our version 1.0 hardware design, it is divided into three main functional areas as we conceived before.

The engineered bacteria are confined within "citrus segments" and encapsulated with bacterial membranes to prevent bacterial leakage. To address potential nutrient depletion, we will use slow-release culture media to ensure optimal growth conditions for the bacteria. Simultaneously, the "citrus segments" will rotate continuously driven by the motor, facilitating thorough contact with the water and the release of OMV.

Area B: Combination Zone, where the OMV
released by the engineered bacteria come
into contact with heavy metal ions.

The water between the citrus segments serves as the region for the binding of OMV with heavy metal ions. Once the hardware is submerged in water containing heavy metal ions, the OMV captures these ions. Multiple layers of nickel nets are also placed between the outer shells to prevent the escape of OMV into the wild environment.

Area C: Collection Zone, where the OMV trapped
with heavy metal ions are collected and deposited.

A significant amount of nickel nets is placed here to collect the OMV that has captured the heavy metal ions. To facilitate the smooth capture of OMV by the collection zone (Area C) nickel nets, a motor-driven propeller is added to agitate the water and drive OMV towards the collection zone.

The cylindrical shape of the hardware reminds us of the traditional Chinese story"Journey to the West" and the Golden Cudgel used by the Monkey King. Similarly, we hope our product can work like the Monkey King who extracts a single hair and produce millions of clones —— a small amount of engineered bacteria can generate a large quantity of OMV, enabling efficient water purification.

The first version of our hardware design showcased quite intriguing innovation and artistic elements. However, after conducting several wet lab experiments, we discovered two significant issues with the first version of our hardware design.
1. The medium came into continuous contact with and leaked into the river, which could result in nitrogen and phosphorus contamination.
2. The engineered E. coli, our target bacteria, had almost no growth capability at ambient water temperature (25°C).
        To address these problems, we had numerous discussions and optimizations that led to the successful design of Hardware Version 2.0.
        To address the issue of E. coli's inability to grow at ambient water temperature, we incorporated a chemically activated heating agent that generates heat upon contact with water. This heating agent is packaged with the bacterial powder and medium in a disposable culture unit that automatically activates upon exposure to water, ensuring optimal temperature for bacterial growth.
        To address the issue of media leakage, we introduced the concept of time. We realized that complete prevention of media leakage during OMV release was not possible. Therefore, we developed a method to control the release of OMV by timing its release when the media content was depleted and the bacterial population was at its peak, approximately 14 hours into the growth cycle. Our hardware operates on a 14-hour cycle and OMV release is timed accordingly, minimizing media leakage.

The Cylinder controlled by a timed motor, moves every 14 hours to replace the old culture unit with a new one. These sealed disposable culture units contain bacterial powder, media, and the heating agent. Both ends of the unit are covered with bacterial filter membranes to prevent bacterial escape.
The valve, also controlled by a timed motor, periodically opens to release OMV.
The square box serves as a temporary collection area for the OMV containing a large number of engineered bacteria. At the end of each cycle, the timed valve opens releasing OMV into Area B.

Area B: Combination Zone, where the OMV released by
the engineered bacteria come into contact with heavy metal ions.

Area C: Collection Zone, where the OMV trapped
with heavy metal ions are collected and deposited.

Nickel nets are placed at the very end of the device to capture and enrich OMVs bound with heavy metal ions.

Procedure ① The cylinder rotates and replaces with a new culture unit, where engineered bacteria grow and reproduce, producing a large amount of OMV.It happens in culture area (area A) ② Released OMV accumulates inside the square box. ③ At the end of the growth cycle, when the culture medium is almost depleted, the timing valve opens, releasing OMV to the combination area (area B), where they capture heavy metal ions in the water. ④ OMV that has bound to heavy metal ions are captured and enriched by the nickel nets in collection area (area C).