We surveyed food vendors from Indonesia and Pakistan and individuals from our diverse student body, which represents 110 countries. From 68 responses, we gained the following insights:
- 78% of individuals have never heard of Shiga Toxin
- 47.5% of individuals were interested in acquiring equipment to detect Escherichia coli in food samples
- 54.2% of individuals were willing to wait 10 minutes to obtain a response from the equipment
- 23.7% of individuals were willing to wait up to 30 minutes to obtain a response from the equipment
- The average price individuals were willing to pay for such a device was $63 USD
2016 Team NYU Abu Dhabi predicted that their device would take up to 45 minutes to complete the reaction. We decided to optimize a reaction such that we could better target the expectations of our potential audience. In this regard, we decided to use the LAMP technique which provides results in 20 minutes.
As part of our design, we realized that deterrents to laboratory testing are not only limited to the length of time required to obtain results. In fact, it was partially due to the high cost of equipment. To address this issue, we aimed to reduce the cost of our device by designing a 3D printed case that houses a Peltier Module Cooler, a cheaper alternative to ITO heating and a more reliable, eco-friendly method than disposable heat packs. We also reduced the volume of our reaction, without sacrificing high sensitivity, to reduce the cost of biological reagents.
We have addressed the concerns brought up through these surveys to the best of our ability. Our final device cost is estimated to cost approximately $65.75USD, and is in the price range suggested by surveyed individuals. Additionally, the reaction time of 20 minutes is a reasonable compromise considering that conventional pathogen detection techniques can take anywhere from hours to days to receive results.
The development of the chip began with the primary idea of reducing the amount of human input needed as much as possible. As the audience of our project mostly encompassed consumers and food vendors, practical lab training was a skill that most did not possess. The idea of the design was to direct a small amount of fluid (the sample) into the reaction chambers in a way that did not require professional laboratory equipment, such as micropipettes or syringes (which could also pose a safety hazard). Over time the design was improved based on results obtained from flow tests conducted on prototypes of each design. The design was optimized over multiple iterations via flow and heating tests to the current design, where the only human input needed is to insert the sample using dropper or Pasteur pipette into the reaction wells, which already have the necessary reagents pre-loaded.
The heat development started with an affordable heat source by using heat packs. Two heat packs that were pricked and insulated were able to provide a temperature of 67˚C for 3 hours, shown in Figure 1. However, the survey data showed that 47.5% of people were only interested in acquiring the device if it was reliable, sturdy and affordable. On average individuals were willing to pay $63 USD, with 44% of individuals indicating that they were willing to pay between $40-150 USD for the device. However, since the heat packs do not have a feedback control, we turned towards a more reliable heat source using Indium Tin Oxide (ITO) heater with PID controller from Cell Micro Controls. This ITO heating method cost $200 USD, a price tag significantly higher than what our surveys indicated that individuals would be willing to pay. To cut down on the price, a Peltier thermoelectric cooler module with an affordable, self-tuned PID controller, in combination with an Arduino nano, was developed. This Peltier heating method cost $46 USD, meeting our target consumer's price range.
Figure 1. Temperature response from 2 heat packs.