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Integrated, Low-Cost and Stand-Alone Micro-Optical System for Grape Maturation and Vine Hydric Stress Monitoring

Periodic Reporting for period 1 - i-GRAPE (Integrated, Low-Cost and Stand-Alone Micro-Optical System for Grape Maturation and Vine Hydric Stress Monitoring)

Reporting period: 2018-12-01 to 2020-05-31

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 18m report period, the first IOT device that monitors parameters related to grape maturation has been fabricated and tested, and first field trials done. The first device for monitoring hydric stress is being deployed in the summer campaign 2020 ( Fig.2 and Fig.3). The fabricated systems 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 monolitically 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, the concept for placing the optical head near the leaf is still being defined. The controller and radio communications unit was implemented through initial ietrations to allow monitoring during the full campaign ( about 2.5 months). First prototypes in the field are using discrete eletronics for the optical signal conditioning. An ASIC is being designed and will replace this unit, allowing signal conditining at the optical head. A multivariate approach is being used to correlate desired grape parameters with diffuse reflectance at the illuminating wavelenghts. Data acquisition in the field is occurring twice a year in Sograpé estates in the Douro valley ( Portugal) and in Argentina. First correlations between optical data and wet chemical analysis for selected grape bunches was already done for data acquired for the summer campaign 2019 ( Douro valley)-results are promising, indicating the advantages ( daily automated monitoring of grape parameters in a variety of plots in the vineyard) as well as points in need of further addressing -large variation of data requiring proper data extraction algorithms.
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. Initial trials are already showing promising results, but also highlight the complexity of dealing with larga data groups that need automated processing to allow decision maling by the vineyard manager.
Fig 2 Optical head with LEDS and photodiodes assembled on a polyimide stripe
Fig 1 Stripe concept incorporating microspectrometers inside the grape bunch
Fig 3 Controller and radio communications unit