Periodic Reporting for period 2 - i-GRAPE (Integrated, Low-Cost and Stand-Alone Micro-Optical System for Grape Maturation and Vine Hydric Stress Monitoring)
Reporting period: 2020-06-01 to 2022-08-31
This project aims at the development of fully integrated, small, low-cost, standalone smart system used for grape maturation and vine hydric stress monitoring. It will consist of an optical detection head ( flexible strip or transparent canopy) connected to the grape bunch or looking at the leaf surface, including power, signal pre-processing, and wireless communications. The detection head will be optically based (UV-VIS to NIR) using an integration of LED sources and photodiode/interference filter arrays at wafer level or wafer package level. Reflectance and fluorescence measurements will be used at various wavelengths to probe spectral signatures for phenols flavonols, clorophile (fluorescence),pH and Brix and other parameters. The project concept initially originated from conversations between Sogrape (a major wine producing company with estates in Portugal, Spain, Chile and Australia ) and INL ( project coordinator). Partners with the required know how were then contacted to bring in and incorporate the various components required at wafer level, wafer package level, component level and system level necessary for the development of an electronic smart system. The consortium as a whole will carry the developed systems into field trials and initial scale up. Fig.1 shows schematically the various components being develloped.
At the 45m final report period, IOT devices that monitor parameters related to grape maturation have been fabricated and tested, and field trials done demonstrating device reliability . IOT devices for monitoring hydric stress were fabricated using both visible and infrared bands (Fig.2 and Fig.3).The fabricated systems ( grape monitoring and water status) include 4 LEDS per module in the uv-visible ( grape monitoring) and visible and NIR ( hydric stress monitoring), an array of photodiodes ( CMOS or a:SiH with monolithically integrated interference filters when required for fluorescence measurements), assembled in a optical microspectrometer head. The assembly has been done either on a PCB or on a polyimide stripe (Fig.2). For monitoring grape maturation, the optical head is placed inside the grape bunch, linked to the external controller and radio communications unit (Fig.3) placed near the trunk. For vine hydric stress monitoring, two concepts were developed to place the optical head near the leaf. The controller and radio communications unit was implemented through initial iterations to allow monitoring during the full campaign ( about 2.5 months). First prototypes in the field used discrete electronics for the optical signal conditioning. An ASIC was developed, tested and deployed in the final optical head prototypes, bringing the signal conditioning near the photodiodes, and was tested in the Summer campaign 2022. A multivariate approach was used to correlate the desired grape parameters with diffuse reflectance at the illuminating wavelengths. For the final correlations, data acquisition in the field was obtained in the summer campaigns of 2020, 2021 and 2022. First correlations between optical data and wet chemical analysis for selected grape varieties was already done ( Brix, potential alcohol, titrable acidity and pH). For water status, thepresent model does not yet allow quantitative prediction of water leaf potential based on the reflectance data.
The autonomous and continuous monitoring of grape and vine parameters throughtout the grape maturation period will create a disruption in the present methodology for grape and vine parameter monitoring usually done by wet chemical analysis in the lab from grape bunches hand picked from selected plots in the vineyard ( grape maturation) or by measuring hydric stress in the vines by extracting water from leaves using mechanical devices. The IOT devices, being low cost (integrated electronics and optics), field deployable, and autonomous during the campaign will allow proper vine ( hydric stress) and grape control defining optimum grape harvesting date selection in the different plots. The results at the end of the project are already catching the attention of experts in the field. The use of the reflectance based IOT technology for grape maturation control was the subject of an innovation prize in Portugal. The initial IP underpinning the technology has now been granted in 10 countries. New IP was submitted and 4 publications concerning component devellopment and optical models were already presented.