Bacterial wilt is a serious disease that poses a severe threat to many economic crops. It often spreads stealthily in farmland and breaks out suddenly, causing huge losses to agricultural production. Most existing detection methods rely on laboratory conditions, which are not only complicated and expensive but also fail to meet farmers’ needs for rapid, simple, and low-cost early diagnosis in the field.

To address this challenge, we designed a hardware solution for field applications. The system can directly collect soil solution samples in farmland and complete detection in a closed environment, without relying on expensive laboratory equipment. Our hardware has undergone three generations of iteration: from the initial electric vacuum pump system, to a simplified syringe-based device, and finally to a lightweight design using disposable vacuum blood collection tubes. The final solution not only reduces cost and size but also effectively solves the problems of sample transfer confusion and operational safety.

In the laboratory replacement stage, we developed several low-cost and reproducible devices, such as a 3D-printed portable shaker and a simple temperature-controlled incubator, to replace costly shakers and incubators. Meanwhile, we designed a rapid inoculation device, which significantly improves the throughput and efficiency of multi-point detection. All of these hardware systems follow the principles of reproducibility and open-source accessibility, providing bill of materials (BOMs), 3D models, and operation manuals, ensuring that other teams or users can easily build and use them.

Our design has always focused on four core goals: low cost (low per-use cost and low initial investment), farmer-friendliness (easy operation and visual results), high throughput and error-free operation (supporting large-scale field monitoring and avoiding confusion), and safety (fully enclosed operation with unified sterilization). Through this hardware system, we hope to achieve rapid early detection of bacterial wilt in the field, providing farmers with practical and accessible tools, and laying the foundation for future green and sustainable agricultural disease prevention and control.

In the early stage of the project, we conducted extensive Human Practices (HP) research. The team visited and interviewed frontline farmers, agricultural extension officers, and plant pathology experts, while also reviewing relevant literature and market reports. Through these exchanges and investigations, we gradually identified the real challenges of bacterial wilt detection in practical agricultural applications.

The farmers we interviewed generally reported that current detection methods rely too heavily on laboratory conditions — soil samples must be collected, transported to professional institutions, and analyzed through complex experimental steps before results can be obtained. This process is time-consuming, labor-intensive, and costly, making it impractical for large-scale field deployment. At the same time, since bacterial wilt often lurks in soil or root systems, symptoms usually appear only after the infection has spread widely, when it is already too late for effective control. Agricultural technicians and experts emphasized that if rapid, visual, and low-cost early detection could be achieved directly in the field, it would not only reduce farmers’ losses but also provide more precise data for regional disease surveillance and prevention.

After consolidating all these findings, we established four core principles to guide the development of our hardware system:

Low Cost In our surveys, almost all farmers emphasized economic feasibility. Therefore, in our design, we focused not only on the low cost of single-use consumables (ensuring that per-test expenses are affordable for farmers) but also on reducing upfront investment, avoiding expensive equipment barriers. We aim for a system that can be deployed in the field with minimal cost, making large-scale adoption possible.
Farmer-Friendly Many farmers lack formal laboratory skills. We must ensure that the hardware is simple and intuitive to operate, minimizing procedural complexity and errors. For result interpretation, we rely on colorimetric reactions that can be visually observed by the naked eye, eliminating the need for costly or complicated detection instruments. The ultimate goal is: farmers can perform and interpret tests directly in the field without training.
High-Throughput & Error-Proof In real field conditions, a single farmer or technician may need to test dozens or even hundreds of sampling points. This requires our system to support parallel multi-point detection, while avoiding confusion during sample labeling and transfer. In other words, we pursue not only high throughput but also error prevention.
Safety & Reliability Safety was a recurring concern throughout our feedback process. Our design ensures that sampling and testing occur entirely within a sealed system, protecting users from potential pathogen exposure while also preventing any engineered or testing strains from escaping into the environment. Furthermore, all consumables and detection tubes can undergo uniform heat inactivation or disinfection, minimizing environmental risk.

Through continuous HP feedback, we gradually integrated these four principles into every stage of hardware iteration. From the earliest concept to the final design, the system has consistently revolved around low cost, farmer-friendliness, high throughput, and safety. These needs not only provided a clear direction for our research and development but also ensured that our design remained closely aligned with user expectations and real-world agricultural applications.

After an in-depth analysis of the detection scenario for bacterial wilt, we divided the overall hardware system into two independent yet closely connected components:

The first part is Field Sampling.

This section focuses on how to efficiently and minimally invasively collect soil solution samples in agricultural environments. We carried out multiple rounds of iteration, evolving from the initial electric pump and collection bottle design to the final lightweight and safe system using disposable vacuum blood collection tubes. The field sampling hardware addresses farmers’ key pain points — difficulty in sampling, risk of confusion, and high cost in field detection.

The second part is Laboratory Alternatives.

Considering the dependence of traditional detection workflows on expensive instruments and laboratory conditions, we developed a series of low-cost and reproducible hardware alternatives, including a 3D-printed portable shaker, a simple temperature-controlled incubator, and a rapid inoculation device that improves multi-point detection efficiency. These devices allow engineered bacteria cultivation and color-based result interpretation to be completed under simplified conditions, enabling the transition of the detection process from “laboratory-dependent” to “field-applicable.”

To accelerate research and iteration, we consistently advanced these two parallel development tracks — the improvement of field sampling and the creation of laboratory substitute devices.

In the following sections, we will introduce the design evolution and final implementation of each part in detail.

3.0 Introduction & Initial Exploration

At the beginning of the project, the first question we considered was: How can we collect soil samples in the field for early detection of bacterial wilt?

In the absence of specialized hardware, we chose the most straightforward approach — using the traditional Luoyang Spade (洛阳铲) for sampling.

However, after multiple trials, we quickly discovered that this method presented a series of serious problems:

• High labor intensity: Digging soil is time-consuming and physically demanding, making it unsustainable for farmers.
• Strong destructiveness: Sampling with the Luoyang Spade causes excessive disturbance to crop roots and soil structure, potentially affecting plant growth.
• Complex follow-up detection: The excavated soil samples often require additional processing and laboratory analysis, making rapid on-site results impossible.
• Difficulty in multi-point sampling: Performing dozens or even hundreds of sampling operations across large farmlands is practically infeasible.

These issues made us realize that traditional soil sampling methods cannot meet the practical requirements of field detection. Continuing to rely on this approach would make it impossible to achieve farmer-friendly rapid testing or large-scale multi-point monitoring.Therefore, we decided to fundamentally change our sampling strategy — shifting from “digging soil” to “collecting soil solution”, and implementing this concept through dedicated hardware design.

From this initial exploration and reflection, our team embarked on the iterative development of field sampling hardware, which ultimately evolved through three generations of progressively optimized solutions.

3.1 Generation 1: Pump + Collection Bottle

After completing the initial attempt of “Luoyang Spade sampling,” we aimed to find a gentler and more repeatable method for obtaining soil solution. Therefore, we built the first-generation field sampling system, which mainly consisted of three parts:

First was the vacuum pump. We selected a relatively large portable electric pump equipped with a built-in battery, capable of operating independently in the field to provide continuous negative pressure for the system.

Second was the soil solution sampler, whose front end was a porous ceramic head with a pore size of approximately 0.2 μm, allowing it to slowly draw in soil solution under vacuum pressure while preventing the intake of large soil particles or debris.

Finally, there was the collection bottle, which had two ports: one connected to the pump for air extraction, and the other connected to the sampler for liquid inflow. The bottle remained sealed, enabling the pump to maintain a negative-pressure environment inside and thus drive the entry of soil solution.

The operational procedure was as follows:

1. Insert the soil solution sampler into the target soil layer.
2. Connect the sampler to the collection bottle and link the bottle to the pump.
3. Turn on the pump to gradually create negative pressure inside the bottle.
4. Under negative pressure, the soil solution slowly passes through the ceramic head, flows through the tubing, and finally accumulates in the collection bottle.
5. After sampling is completed, turn off the pump, detach the collection bottle, and bring it back to the laboratory for further analysis.

A detailed process can be viewed in the demonstration video:

In theory, this design was sound and successfully demonstrated the feasibility of collecting soil solution instead of digging soil samples. Compared with the traditional Luoyang Spade (洛阳铲) method, it caused significantly less damage to root systems and soil structure, while also reducing dependence on manual sample processing.

However, after multiple tests, we gradually realized that this first-generation system had several serious limitations.

First, it was bulky and inconvenient. The pump and collection bottle were both large, and the long connecting tubes made the entire setup cumbersome during field operation. Each sampling required carrying heavy components, which was impractical for farmers.

Second, it was time-consuming to operate. Due to the long and wide tubing, liquid took a long time to enter the collection bottle. In wet soils, it usually required several minutes to gather enough liquid, while in dry soils, the vacuum often failed to draw in any liquid at all — a common situation in real agricultural fields, severely limiting its applicability.

Third, there were reliability issues with the pump. Although we selected a vacuum model, continuous operation under high negative pressure often led to overheating, excessive noise, or failure. Replacing or repairing the pump was costly, further hindering large-scale adoption in agricultural settings.

Finally, it suffered from high cost and low throughput. The collection bottle and pump were both relatively expensive components, and the system could only handle one sampling point at a time — after each collection, the entire setup needed to be reset before proceeding to the next point. For farmlands requiring dozens or even hundreds of sampling locations, such low efficiency was clearly unacceptable.

In summary, while the first-generation system achieved the conceptual breakthrough of shifting from “digging soil” to “extracting solution,” it exposed numerous practical shortcomings. These limitations not only highlighted the vast gap between “laboratory feasibility” and “field usability” but also directly motivated the rethinking and redesign that guided our subsequent hardware iterations.

3.2 Generation 2: Syringe-Based Simplification

During the practical operation of the first-generation system, we gradually realized that the combination of an electric pump and collection bottle had significant drawbacks: bulky equipment, long sampling time, frequent pump failures, and the inability to meet the demand for multi-point field monitoring. To make the sampling method lighter and more cost-effective, we explored a simplified design approach — using the negative pressure generated by a syringe itself to perform sampling.

The second-generation system consisted of three core components:

• Disposable Syringe: Served as the main negative pressure device. Pulling the plunger created a vacuum, replacing the function of the pump and collection bottle.
• Narrow Tubing (<1 mm): Connected the syringe to the soil solution sampler. Compared to the thicker tubing used in the first generation, the narrower one significantly reduced dead volume, allowing for faster and more efficient liquid collection.
• Soil Solution Sampler: Retained the same design as in the first generation, featuring a porous ceramic tip as the sampling probe.

In actual operation, the user first inserted the sampler into the soil and then connected it to the syringe. By pulling the plunger backward, negative pressure formed inside the syringe, drawing soil solution into it. To maintain the vacuum state, we adopted a simple method: using a small wooden stick or clip to hold the plunger in place and prevent it from rebounding. Over time, enough sample accumulated in the syringe, after which the user could remove the sampler and detach the syringe.

This generation achieved significant improvements in portability and affordability. The cost of a disposable syringe was only a few Chinese cents, far cheaper than the pump and collection bottle. Its small size and light weight allowed operators to easily carry multiple syringes in the field, enabling parallel multi-point sampling. Moreover, since it required no power supply, the second-generation system was also more reliable than the first.

However, large-scale testing revealed new problems.

First, the sample transfer process was cumbersome and risky: the liquid collected in the syringe had to be transferred into a centrifuge tube or vacuum tube for subsequent testing. This increased operational complexity and introduced risks of contamination and mix-ups, especially during high-throughput sampling.Second, sample information management became confusing. When dozens or even hundreds of sampling points needed testing, keeping accurate records and distinguishing between samples proved difficult — issues like “forgetting to label a syringe” or “mixing up transfer order” occurred frequently.Finally, manual workload remained high. Although a single syringe was easy to use, under high-throughput conditions the repetitive steps of transferring and labeling samples still demanded significant labor.

Thus, while the second-generation system solved the issues of portability and cost, the new bottleneck shifted toward sample management and operational efficiency. This directly inspired our next idea: could we design a container that eliminates the transfer step and comes with a built-in labeling system? This concept ultimately led to the development of our third-generation sampling system.

Advantages	Limitations
Extremely low cost (sampling completed for only a few cents)	Samples require transfer, adding extra steps
Lightweight and easy for farmers to carry	Easy to confuse or forget labels during multi-point sampling
No power supply needed, high reliability	Heavy manual workload in high-throughput operations
Can be operated in parallel, suitable for multi-point sampling	Risk of contamination during sample transfer

3.3 Generation 3: Vacuum Blood Collection Tubes

Through the testing of the first two generations, we gradually clarified the true needs of field sampling: the device must be lightweight, low-cost, easy to operate, avoid transfer and confusion, and ensure full-process safety and sealing. Based on these requirements, we developed the third-generation sampling system, ultimately adopting disposable vacuum blood collection tubes as the core component.

Hardware Composition

• Vacuum Blood Collection Tube: Pre-vacuumed and sealed at the factory, with a rubber stopper that can be pierced by a needle; each tube carries a unique label or barcode for sample traceability.
• Sampling Needle Adapter: Connects the soil solution sampler to the blood collection tube, allowing the sampler to be directly inserted into the tube during sampling.
• Soil Solution Sampler: Responsible for extracting the soil solution and transferring it through the needle into the blood collection tube.

Design and Usage Method

During field operation, the farmer simply inserts the soil solution sampler into the target soil layer, then connects it to the vacuum blood collection tube using the sampling needle adapter. The vacuum inside the tube immediately creates suction, drawing the soil solution directly into the tube.

The entire process is completely sealed, requiring no power supply, no manual suction, and no transfer steps. After sampling, the operator simply tears off the label or barcode from the blood collection tube and attaches it to a record sheet, thus completing sample collection and labeling simultaneously. The sealed tubes can then be taken directly back to the laboratory for testing, greatly simplifying the workflow.

System Advantages

The third-generation system achieved significant improvements and breakthroughs over the previous two generations:

• Transfer-free: Samples enter the tube directly, avoiding contamination and confusion caused by secondary transfers.
• Pre-labelled Management: Each tube has a unique ID, making multi-point sampling management and traceability more efficient and reliable.
• Ultra-low Cost: Each sampling costs only about 0.2 RMB, far lower than the high cost of the first-generation system.
• Portable & Easy-to-use: Compact structure and intuitive operation — farmers can use it without training.
• Safe & Sealed: The entire process, from sampling to storage, occurs in a closed environment, ensuring both operator safety and sample stability.
• Eco-friendly Reusability: Made primarily of plastic and glass; over 80% of components are recyclable, reducing environmental impact.

In summary, the third-generation system is not only experimentally feasible but also truly field-deployable. It fully satisfies the four core principles — low cost, farmer-friendliness, high throughput, and safety — making it the final version of our field sampling hardware.

3.4 Comparison & Evolution of Three Generations

Through the continuous iteration of three generations of systems, we achieved a crucial transformation from a “laboratory-oriented concept” to a “field-deployable solution.”The first-generation system demonstrated the feasibility of collecting soil solution, but it was bulky and expensive, making it unsuitable for real-world agricultural use.The second-generation system made a qualitative leap in portability and cost reduction, yet still suffered from issues in sample management and operational complexity.The third-generation system combined the strengths of the previous two, completely solving the core challenges of portability, cost, safety, and high-throughput capability, and truly fulfilled the four core principles: low cost, farmer-friendliness, high throughput, and safety.

This evolutionary process not only reflects our team’s engineering mindset in hardware development, but also showcases our iterative process of field testing, failure, and optimization.Behind each iteration lies a genuine understanding of real-world problems and a systematic approach to designing practical solutions.

Criteria	Generation 1: Pump + Collection Bottle	Generation 2: Syringe-Based	Generation 3: Vacuum Blood Collection Tube
Portability	Bulky, complicated to operate	Lightweight, easy to carry multiple units	Extremely compact, one-hand operation
Cost	High (requires pump and bottle)	Very low (a few cents per sample)	Ultra-low (~¥0.2 per sample)
Power Dependency	Requires battery power	No power required	No power required
Sampling Speed	Slow; ineffective in dry soils	Faster, but requires transfer	Fast and transfer-free
Sample Management	Single-point, prone to confusion	Multi-point, but relies on manual recording	Pre-labelled tubes, clear traceability
Safety	Partially open, risk of leakage	Risk of contamination during transfer	Fully sealed, safe and reliable
High-throughput Capacity	Not feasible	Partially feasible, high manual burden	Fully supports large-scale parallel sampling
Overall Evaluation	Proof-of-concept	Breakthrough in cost & portability	Final practical solution

4.0 Introduction

A complete molecular biology laboratory typically requires a wide range of expensive and precise instruments, such as microplate readers, fluorescence microscopes, incubators, shakers, and high-precision pipettes. While these instruments are essential in research environments, they are completely impractical for field applications. On one hand, their high cost makes them unaffordable for farmers; on the other, their complex operation makes them inaccessible to users without professional training.

In our project, we have already reduced the dependence on instruments such as microplate readers and fluorescence microscopes by employing colorimetric visual detection, significantly lowering the experimental threshold. However, even with these simplifications, we found that several types of equipment remain indispensable:

• Shaker: During bacterial culture, continuous shaking ensures proper liquid mixing and gas exchange, allowing the engineered bacteria to maintain optimal aerobic growth. Without a shaker, the culture rapidly becomes anaerobic, leading to weakened or even absent colorimetric reactions.
• Incubator/Fermentation Chamber: Temperature control is equally crucial. Although engineered bacteria can survive at lower temperatures, they exhibit the best growth rate and metabolic activity at 37°C. Without a stable thermal environment, the detection process becomes slower and less reliable.
• Inoculation Device: In field testing, we need to rapidly and accurately introduce engineered bacteria into multiple samples. While traditional pipettes offer precision, they are inefficient and error-prone when handling dozens or even hundreds of samples, often causing cross-contamination. Thus, an efficient and controllable inoculation method is indispensable.

Based on these insights, we defined the development goal of our laboratory substitution hardware:

To design low-cost, portable, and user-friendly alternatives for the three essential instruments — the shaker, incubator, and inoculation device — while preserving their core functionality.

Through the integration of these devices, we aim to construct a “simplified laboratory” that allows bacterial wilt detection not only to be validated under laboratory conditions but also to be practically applied in the field, bringing real value to farmers.

4.1 Low-cost Shaker

In a conventional molecular biology laboratory, a shaker is one of the essential core devices. Through continuous oscillation and gas exchange, it ensures that the engineered bacteria in the culture medium grow stably under aerobic conditions. However, commercial laboratory shakers usually cost from several thousand to tens of thousands of RMB, and many designs are patent-restricted, making them nearly impossible to promote among farmers or in low-resource settings.

To address this issue, under the guidance and support of our instructors, we developed a low-cost shaker using 3D printing and basic motor components. The structural design is simple yet functional, and it mainly consists of three parts:

• Base and Power System: The base is 3D-printed, housing a rechargeable battery (compatible with standard 5V chargers) and a motor. The motor’s speed is adjusted via a continuously variable resistor switch, rather than being limited to fixed-speed settings as in conventional shakers. Although this system cannot provide precise RPM readings, it dramatically reduces cost while still meeting the requirements for bacterial culture. The motor’s high-speed rotation is transmitted through a speed-reduction mechanism to the upper structure, maintaining an overall rotational speed of around 100 rpm.
• Transmission Structure: The motor connects to a triangular support frame through bearings. A dual L-shaped linkage converts the rotary motion into gentle circular oscillations, producing continuous and stable shaking. The triangular frame design ensures mechanical stability under various load conditions.
• Carrying Platform: The top layer of the shaker is an interchangeable platform. In our experiments, we primarily used a foam plate with pre-cut holes to securely hold vacuum blood collection tubes. Future users can replace this plate with other designs to fit EP tubes, centrifuge tubes, or other containers.

Assembly Demonstration of the 3D-Printed Shaker

This short video showcases the assembly and testing process of our 3D-printed low-cost shaker.

The demonstration clearly shows that the device is fully functional, capable of maintaining stable and continuous oscillation.

By documenting each step of the assembly, this video aims to assist future iGEM teams or researchers who wish to replicate or improve the design.

It serves as both a technical reference and a proof of feasibility for our low-cost hardware innovation.

In actual operation, this shaker provides an incubation environment similar to that of a commercial laboratory shaker, but with a dramatically lower cost and greater accessibility. Its production cost is far below that of commercial models, and since it does not rely on proprietary components, any team can reproduce or modify it using open-source design files. More importantly, this design not only addresses our needs for bacterial wilt detection, but also offers a reusable and scalable low-cost hardware platform for future iGEM teams and educational purposes.

Significance Summary:

• Extremely low cost, suitable for resource-limited settings;
• Simple structure, easy to maintain and reproduce;
• Flexible functionality, adaptable to various container types;
• Open-source design, enabling future iteration and application by other teams.

4.2 Low-cost Incubator

In bacterial culture experiments, temperature control is also an indispensable factor. Conventional laboratory incubators can maintain the set temperature with extremely high precision, but their prices usually range from several thousand to tens of thousands of RMB, making them unaffordable for field use or low-resource environments. In practice, for our engineered bacteria, precise control to 0.1°C is not necessary — maintaining a stable environment around 37°C is sufficient for effective growth. Therefore, we designed a low-cost incubator to replace expensive commercial incubators.

Structure and Components

The design of this incubator is simple yet efficient, consisting mainly of the following parts:

A. Heating and temperature control module. It includes a power adapter, digital temperature controller, heating pad, and a metal temperature probe (visible on the right). B. Working status of the system. The controller, attached to the back of the housing, shows a stable chamber temperature of around 37 °C. Two cables connect through the rear wall — one for the heating pad and one for the temperature probe. C. Internal view of the incubator. The heating pad and plastic insulation plate are visible at the bottom, along with a UV sterilization lamp on the left side. D. The incubator during operation. The transparent cover allows direct observation of the 3D-printed shaker and vacuum sampling tubes placed inside for temperature-controlled culturing.

Usage Method

The operator simply places the shaker and sample tubes inside the chamber, closes the transparent door, connects the power supply, and sets the temperature range. The heating pad and control system automatically maintain the internal temperature around 37°C. Under this condition, the engineered bacteria can grow efficiently and complete the colorimetric reaction, with minimal manual intervention.

Significance Summary

• Extremely Low Cost: The total cost of a single incubator does not exceed 50 RMB, far cheaper than commercial devices.
• Functionally Adequate: Although less precise than research-grade equipment, it fully meets the requirements of our detection process.
• Simple and User-friendly: Easy to operate; farmers or field technicians can use it without professional training.
• Transparent Observation: Allows continuous monitoring of internal samples, improving practicality and safety.

Used together with our portable low-cost shaker, this incubator can effectively replace conventional laboratory equipment, providing a solid foundation for a simplified “field laboratory” suitable for on-site bacterial wilt detection.

4.3 Rapid Inoculation Device

In laboratory operations, inoculation (adding engineered bacterial strains into samples) is typically performed using a micropipette. While this method offers high precision, it becomes inefficient, cumbersome, and error-prone when dealing with dozens or even hundreds of samples. In high-throughput testing, repetitive pipetting not only consumes time but also increases the risks of cross-contamination or sample confusion, potentially compromising the results. To overcome these limitations, we designed and built a rapid inoculation device based on a peristaltic pump.

Device Design

The core of this device is a peristaltic pump:

• The input end is connected to a tube containing pre-activated engineered bacterial solution.
• The control system adjusts the flow rate via voltage regulation, combined with a preset operation time, achieving single-dose quantitative delivery. During calibration, we conducted multiple tests using centrifuge tubes and set the parameters so that each injection outputs approximately 5 mL, consistent with standard laboratory operations.
• The output end is designed as a pen-shaped interface fitted with a needle. The needle can pierce the rubber cap of a vacuum blood collection tube, enabling sealed and contamination-free injection.
• Button Operation: A button on the pen interface triggers the pump. Each press activates the peristaltic pump for a preset duration, delivering a fixed volume of engineered bacteria (about 5 mL), thereby completing a rapid and quantitative inoculation.

Usage Method

The operator simply aligns the pen-shaped interface with the cap of the vacuum tube and presses the button to complete one standardized injection within a few seconds. The needle is then withdrawn, and the operator can proceed to the next sample immediately. The entire process eliminates repetitive pipetting, ensures consistent dosing, and minimizes operational error. In our testing, this device performed over five times faster than traditional pipetting, significantly improving multi-sample processing efficiency.

Significance Summary

• High Efficiency: Each inoculation takes only a few seconds, drastically reducing operation time.
• Standardization: Dual control of voltage and time ensures consistent injection volume (≈5 mL).
• Safety: The needle injects directly into the sealed tube without uncapping, minimizing contamination risk.
• User-friendly: Simple “aim and press” operation allows farmers or non-professionals to use it easily.
• Cost-effective: The total cost is approximately 400 RMB, making it suitable for farm-scale applications.

This rapid inoculation device eliminates the bottlenecks associated with traditional pipetting in high-throughput detection, providing our “simplified laboratory” with a fast and reliable solution for sample handling.

4.4 Summary

In the overall design of field detection, we not only needed to solve the problem of sample collection, but also had to address the laboratory dependency in the sample processing and analysis stages. In traditional laboratories, equipment such as shakers, incubators, and inoculation tools are indispensable, yet their high cost and complex operation make field deployment nearly impossible.

Through repeated analysis and iteration, we proposed and implemented three categories of low-cost alternative solutions:

• Low-cost Shaker: Utilizing 3D printing, motors, and stepless speed control, this device provides an equivalent oscillation environment to laboratory shakers, ensuring that engineered bacteria grow under aerobic conditions.
• Low-cost Incubator: Constructed using a transparent plastic box, heating pad, and temperature controller, it maintains a stable environment around 37°C, meeting the thermal requirements for bacterial cultivation.
• Rapid Inoculation Device: A pen-shaped system based on a peristaltic pump, enabling one-click, quantitative, and rapid injection, greatly enhancing the efficiency and reliability of multi-point detection.

Demonstration of the Complete Laboratory Workflow

This video presents the full experimental workflow using our low-cost 3D-printed shaker and temperature-controlled incubator. It demonstrates how soil solution samples are loaded, mixed, and incubated at 37 °C under controlled conditions. After several hours of shaking, some tubes turn blue, visually indicating the presence of quorum-sensing signals related to bacterial wilt infection. By checking the labels on the vacuum tubes, users can easily trace and identify specific plants or field locations with a higher risk of Ralstonia solanacearum contamination.

These three devices not only maintain functional equivalence with traditional laboratory equipment but also feature outstanding advantages of low cost, portability, ease of operation, and farmer accessibility. Together, they form a “simplified laboratory”, enabling Ralstonia solanacearum (bacterial wilt) detection to move beyond laboratory settings and become truly feasible for field deployment.

More importantly, these alternative hardware systems possess universality and reusability: they not only serve the goals of our project but also provide open and sustainable solutions for future iGEM teams as well as for scientific education and research in low-resource environments.

Throughout the entire design and implementation process of our project, we have consistently placed biosafety and regulatory compliance as top priorities. Although our hardware solutions are primarily intended for field-based detection, we fully recognize that the engineered bacteria involved pose potential risks. Therefore, we implemented multi-layered preventive measures to ensure that no harm could occur to the environment or to users.

First, in all stages of design, we strictly limited the use of engineered bacteria to controlled laboratory environments. All field applications involve only the collection and preservation of soil samples, without releasing any live engineered microorganisms into farmland.

Second, during hardware development, we introduced an additional safety inactivation step. Specifically, our low-cost incubator is equipped with an internal ultraviolet (UV) lamp. After cultivation and colorimetric reactions are completed, and before the operator opens the incubator, the system performs a round of UV sterilization, ensuring that all engineered bacteria inside are completely inactivated. This guarantees that samples lose biological activity before removal, minimizing any risk of environmental dissemination.

Finally, our hardware design fully complies with iGEM biosafety requirements, ensuring that the system’s openness does not lead to any biological leakage. Through simple and low-cost design principles, we achieved safety, containment, and practicality. We hope this practice can serve as a reference model for future biosafe biological detection in low-resource settings.

Note:All photos and videos shown in this documentation are for demonstration purposes only.They do not contain any live engineered microorganisms.All experimental procedures were performed under strict biosafety compliance,and visual materials were created solely to illustrate hardware functionality for educational and research presentation purposes.

User Manual

To ensure that our hardware system can be directly applied in real-world agricultural contexts, we prepared a User Manual specifically designed for farmers and frontline practitioners. This manual provides step-by-step instructions — from field sampling, handling of vacuum tubes, and operation of the incubator, to the interpretation of colorimetric results. Written in simple, farmer-friendly language and illustrated with diagrams, it allows users without prior laboratory training to confidently perform the detection process.

Developer Guide

n addition to the user-oriented document, we also prepared a Developer Guide aimed at iGEM teams and researchers who wish to replicate, adapt, or expand upon our work. This document includes detailed procurement lists, assembly tips, troubleshooting advice, and lessons learned during our own development (including pitfalls to avoid). By making these resources available, we hope to lower barriers for future teams, accelerate iteration, and promote open collaboration across the iGEM community.

Cost

Throughout the development of our hardware systems, we have continuously optimized for cost-effectiveness to ensure true feasibility in field deployment. Both the field sampling units and the laboratory substitution devices achieved dramatic reductions in cost while maintaining functionality and reliability.

Field Sampling Systems

Generation 1 (Pump + Collection Bottle): The first prototype required a powered air pump, thick-walled collection bottle, and tubing. The total equipment cost ranged from ¥500–¥800 CNY (~$70–$110 USD) per set, making it unsuitable for large-scale or farmer use.
Generation 2 (Syringe System): This version reduced the cost substantially — each sampling event cost only a few cents (¥0.3–¥0.5 CNY / $0.04–$0.07 USD). However, it still required manual liquid transfer and sample labeling, which limited its efficiency.
Generation 3 (Vacuum Blood Collection Tube System): The final system achieved both high efficiency and ultra-low cost. Each sampling tube costs only ¥0.2 CNY (~$0.03 USD). Although the soil solution suction needle itself costs ¥130 CNY (~$18 USD), it can be reused over 1,000 times, resulting in a per-use cost of less than ¥0.15 CNY (~$0.02 USD) — effectively eliminating cost barriers for field deployment.

Laboratory Substitution Devices

Low-cost Shaker: Constructed with basic motors and 3D-printed or modular parts, costing only ¥50 CNY ($7 USD).
Low-cost Incubator: Built with a heating pad, plastic casing, and temperature controller; total cost <¥50 CNY (<$7 USD), compared to commercial incubators priced at over ¥10,000 CNY (~$1,400 USD).
Rapid Inoculation Device: Powered by a peristaltic pump and precision controls, costing ¥400 CNY ($55 USD). However, in the next-generation version using lyophilized engineered bacteria, this device may no longer be necessary, further reducing overall expenses.

Overall, our hardware suite delivers equivalent functionality to laboratory-grade systems at less than 1% of their traditional cost, making large-scale deployment economically viable even for small-scale farmers.

Deployability

Our entire system was designed with real-world usability in mind. Each device features lightweight construction, modular assembly, and intuitive operation — users can perform sampling and detection without specialized training. The materials are low-cost and globally available, ensuring stable supply and ease of reproduction.

These characteristics — low cost, minimal technical requirements, high adaptability, and environmental friendliness — make our hardware system not only feasible for laboratory use but also truly deployable in the field, empowering farmers to perform reliable, on-site disease monitoring.

After completing the three generations of our field sampling hardware and the development of laboratory substitution devices, we recognize that there is still significant room for optimization and expansion. In the future, we plan to advance our system in the following directions:

1. Lyophilized (Freeze-dried) Engineered Bacteria Powder

Although our current rapid inoculation device is highly efficient, it still requires additional equipment and manual operation. In the next phase, we plan to convert the engineered bacteria into a freeze-dried powder form, preloaded directly into the vacuum blood collection tubes. After soil solution sampling, farmers will no longer need the inoculation device — they will simply allow the collected soil solution to react with the lyophilized bacteria within the sealed tube. This modification will eliminate equipment dependency, making the system lighter, more portable, and easier to deploy, significantly lowering the threshold for widespread application.

2. Digital Tracking and Management

In large-scale agricultural fields, hundreds of sampling points often need to be monitored simultaneously. To avoid recording errors and data confusion, we plan to develop a mobile application (App) that will:

• Automatically label samples by scanning the QR code or barcode on each collection tube;
• Record GPS coordinates of each sampling point in real-time;
• Synchronize sample data with field photographs, forming an intuitive geo-visual database.

This digital management system will greatly improve the efficiency and reliability of high-throughput detection, while providing farmers with data-driven visual analysis tools for better decision-making in disease monitoring and prevention.

3. Modular and Compatibility Optimization

We plan to further modularize the structure of the shaker and incubator. For example, by designing interchangeable shaker plates compatible with various container types such as centrifuge tubes, EP tubes, and vacuum blood collection tubes, we aim to enhance the universality and reusability of our equipment.

4. Sustainability and Environmental Friendliness

While maintaining low costs, we also intend to explore the use of more recyclable materials and low-energy designs to reduce the environmental burden caused by disposable consumables. For instance, integrating biodegradable materials into the vacuum blood collection tubes, or incorporating energy-efficient electronic control systems into the devices, will make the overall design more aligned with the concept of green development.

Summary

These future plans will not only simplify operations and reduce costs, but also expand the system’s value in large-scale applications and digital agriculture. Through continuous iteration, we hope to make this hardware system a practical daily tool for farmers, providing a sustainable solution for early prevention and control of agricultural diseases.

Throughout the development of our hardware, we carefully considered the iGEM judging criteria and ballot questions to ensure our work aligns with the expectations of the Hardware award. Below is a point-by-point response to the evaluation questions:

1. Does the hardware you developed address a need or problem in synthetic biology?

Our hardware directly addresses the challenge of deploying synthetic biology tools outside of controlled laboratory environments. Specifically, it provides a low-cost, portable, and farmer-friendly solution for the early detection of bacterial wilt in the field. By enabling reliable detection without expensive lab instruments, our system tackles a critical barrier to the real-world application of synthetic biology in agriculture.

2. Did the team conduct user testing and learn from user feedback?

Yes. Through Human Practices activities — including interviews with farmers, consultations with agricultural experts, and field surveys — we identified four core design principles: affordability, farmer-friendliness, high-throughput capability, and safety. These insights directly guided our iterative improvements from the first to the third generation of the sampling device, as well as the development of our laboratory substitution devices. Our hardware design was therefore not created in isolation but shaped by continuous user feedback.

3. Did the team demonstrate utility and functionality in their hardware proof of concept?

We developed and tested three generations of field sampling devices and built functional prototypes of a low-cost shaker, incubator, and rapid inoculation device. Each device demonstrated equivalent functionality to conventional laboratory equipment while drastically lowering cost and complexity. Comparative tests confirmed their efficiency, robustness, and safety, providing clear proof of concept for their utility in real-world applications.

4. Is the documentation of the hardware system sufficient to enable reproduction by other teams?

Yes. On our Wiki, we provide detailed documentation of the design rationale, construction process, usage protocols, and iteration steps for all devices. In addition, we prepared a user manual and replication guide to ensure other iGEM teams can reproduce our work at minimal cost. This level of documentation ensures that our hardware is not only a one-time solution but also a reproducible and sustainable contribution to the iGEM community.

Conclusion

Our hardware system addresses a real-world problem, incorporates user feedback, demonstrates practical functionality, and provides sufficient documentation for replication. Together, these achievements strongly align with the judging questions for the Hardware award, showcasing how synthetic biology can be extended into real-world agricultural applications through thoughtful engineering design.