Team:SCAU-China/Hardware
Overview
Our hardware is equipped with biological workspace, electrochemical sensor, propulsion system and Navigation Satellite System (GPS+BDS, BeiDou navigation satellite System). The device could produce space and protection for our Chlamydomonas to live and work in waters, meanwhile, it could also accomplish multiple functions such as environment monitoring, positioning cruise and so on. Under the guidance of models from DryLab, we could obtain an accurate metal ion concentration in a specific position in real time. Further, combining with the navigation of GPS+BDS and propulsion by motors, we could achieve whole water area survey, pollution distribution mapping and initiative cruising.
Figure 1: Rendering diagram of the hardware
Video 1: Actual environment test of the third generation hardware
Video 2: 3D structure of the third generation hardware
Basic Structure
The basic structure of our device is a two-storey basket. Outer storey is acrylic with holes, providing protection to inner basket while allowing material in and out. Inner storey is the living space of our engineered Chlamydomonas, which is made up of semipermeable membrane, allowing small molecule including nutrition and Cadmium ion passing through, while cells are obstructed in the inner storey. The semipermeable membrane will be sealed tightly by rubber rings to the basket to avoid cell leakage. Between the inner and outer storey, a piece of small-density sponge layer will be set to further filter small and sharp matter avoiding blocking or damaging of the membrane. Out of the basket, plastic floats are equipped to produce buoyancy.
Figure 2: 3D structure of the hardware
Figure 3: Physical structure and rendering diagram of the hardware
Advanced Function
To extend the function of the device fitting the need of actual application, we specially designed and equipped electrical system, which is consisted of microcomputer, sensory unit, propulsion unit and navigation unit.
Sensor unit contains electrochemical sensor and ultrasonic ranging module (type US-015). Electrochemical sensor could measure metal ion concentration in real time. Ultrasonic ranging module could detect obstacles on the way and offer distance information assisting microcomputer making avoiding decision.
Figure 4: 3D structure of the second generation hardware(A) and physical structure (B).
Video 3: 3D structure of the second generation hardware
Propulsion unit is made up of 2 motors on the both sides of the device. Under the control of ESC (Electronic Speed Control), propulsion force of each motor could be adjusted to consequently make the whole device forward, reverse and differential steering.
Navigation unit is in GPS+BDS dual-mode (type ATK-S1216F8-BD-V23). It can receive positioning information including accuracy, latitude, height, speed, number of positioning satellites, visible satellites, UTC time and so on from two satellite systems, allowing us to grasp the movement status of the device.
Figure 5: Schematic diagram of the third generation hardware.
Workflow
When we launch the device, the navigation unit will start receiving and recording the latitude and longitude coordinates. Since then, location of the device in the water will be intermittently collected and the movement track will be drawn.
At the meanwhile, metal ion concentration will be measured by electrochemical sensor. The raw data of concentration will be uploaded to the central server. Processing the Mix Model from DryLab, we could obtain accurate concentration which will be inputted into Stress Model to predict working limit and device withdrawing moment.
A broad water area will be divided into several equal hexagon subarea. Since hundreds of devices will be launched into water, and each device is responsible for one subarea, so that the entire water area can be covered. Coordinates from navigation unit and measurement data from sensor unit will be sent to central server and be integrated, output a map of distribution.
Figure 6: Workingflow diagram of the hardware
Human-device Interaction
To conveniently control devices in remote, we designed an APP for tablets and mobile phones. There are Remote Control Mode, Smart Mode for users to monitor and remotely control devices. Remote Control Mode allows users to manually control the whole process including speed, moving direction, and cruising route. Smart Mode can achieve full automation of device cruising and working. When the work is finished, a report contains population curve of chlamydomonas in this task and the working limit prediction will be shown.
Video 4: Application of MESEG
Biosafety
To prevent engineered chlamydomonas cell leakage, we equipped semipermeable membrane in the inner storey. The pore size of the semipermeable membrane (5 μm) is smaller than the cell size. Thus, it could limit the activity space of cell.
Besides, we also use sodium alginate to encapsulate and fix cells. For more information, see the Safety page.
Environmental Friendly
The material of the device are acrylic, PE and PLA which are recyclable. PLA could be made from starch raw materials extracted from renewable plant resources (such as corn). It has good biodegradability which can be completely degraded by microorganisms in nature generating carbon dioxide and water without polluting the environment.
Besides, we use solar energy as the power source of the hardware, which is green and inexhaustible.
Hardware Update Log
References
- Liu Y, Meng F, and Liu Y, et al. (2020). Modification and Application Progress of Cellulose Acetate Composite Membrane. Plastics 49, 127-130.
