Improvements

We applied some methods to improve our VOC device and designed the future plan for further optimization.

We have constructed a low-cost thermal enrichment unit.

The thermal enrichment unit consists of a Tenax filled tube, a heating device and its associated controlled gas path. Tenax®TA is a commonly used adsorbent for biological VOC detection, which is a porous polymer that can adsorb gases. It adsorbs VOCs at room temperature, and quickly release the gases at about 280℃, which is exactly the way we can achieve the enrichment.

Fig.1 A photo of our thermal enrichment unit

The schematic diagram of the device we designed are shown in the following figure: During the adsorption process, the air pump and valve are opened and the outside air is pumped into the Tenax tube,and VOCs will be attached. In the desorption process, another air pump and valve are opened,and pumped the air cleaned by a gas purification tube which is filled by molecular sieve. In the meanwhile, the heating plate is activated. This device is equipped with a thermostatic control system and it can keep the temperature to 280-300oC during heating, It can also display the current temperature of the tenax tube in real time. The desorbed gas then is taken out with the clean air and sent into the detector.

When using the unit, push the yellow button for adsorption and the red for desorption. The small OLED screen will show the current status and the remaining time.

Fig.2 The flow chart of our thermal enrichment unit

Our thermal enrichment unit can cooperate with our VOC device, to enhance its response value by enriching the VOCs. What’s more, the adsorption time of VOCs can be adjusted to accommodate different detection environments. At the same time, we can use different fillers in the tube to shield the interference of background VOCs.

We combine the weather condition with our disease estimation model.

The weather situation is highly related to the outbreak of tobacco black shank. According to our HP activities in Hunan Tobacco Bureau of the field study, we learn that in the continuous high temperature and humidity, especially when the temperature is 28 ~ 32℃, is most common for tobacco black shank to outbreak. Therefore, we measure the weather information on the main device and take it into consideration when performing disease diagnosis. In the event of sustained high temperature and humidity, it will gives a higher probability value of disease judgments.

Future work

We'll introduce specific gas sensing pathways into our device.

A specific cell-dependent gas sensor is a more reliable than broad-spectrum electronic VOC sensor. Therefore, we will try a new method of adding genes that can generate gas markers behind the Trichoderma hyperparasitic promoters. When our Trichoderma atroviride encounters pathogens, it will activates this promoter, and these gas tags will be released and detected by our specific cell sensors. According to the concentration and duration of the gas tag, it can determine the health situation of plants more accurately.

We'll miniaturize our device and reduce the cost.

Because of the major limitation, we still can’t integrate all the circuit. In the future, we will work with more parties to make the equipment more miniaturized, and further reduce the cost of equipment to achieve a wider range of applications. We’ll make all efforts to achieve this goal.