PLUG AND PLAY, INEXPENSIVE WATER POTENTIAL SENSOR FOR WIDE USE IN SMALL-STEM CROPS

The focus of this SBIR project is to develop the FloraPulse µTensiometer for widespread use in crops with small stems. We aim to enable ubiquitous measurement of water potential in commercial, scientific and consumer applications. To this end, we propose to redesign the sensor and installation method for small-stems and field test it in numerous crops.Aim 1: Modify the microchip design to increase response speed and sensitivity (Fig. 4). To achieve ubiquitous use of our probe, we will redesign the microchip to dramatically increase response speed by up to 25x and sensitivity by up to 30x. A faster, more sensitive microchip will enable (1) water potential measurement in annual crops and typical soils that have high (wet) water potential, (2) eventual shrinking of the microchip die, which is currently large and expensive by microfabrication standards, (3) improved long-term sensor accuracy and stability, (4) capture of smaller water potential features the sensor is currently too slow to measure and (5) lower-cost electronics to power and read the microchip.Aim 2: Develop hardware and methods for easy, quick installation in small stems (Figs. 5 - 7). In this aim we will develop an installation method that is 10x faster (1 minute), requires no power tools and produces a wound 25x smaller (3 mm diameter x 7 mm deep) than our current method. These improvements will be tested with an 'artificial stem' developed to test the critical measurement parameters in the laboratory. The improved method will help increase accuracy and customer adoption with our existing (large-stem) crops and enable servicing of numerous crops whether annuals or young perennials.Aim 3: Test critical wound response in numerous small-stem crops. Once the sensor installation method has been developed, the biggest unknown is the wounding response for each plant species. Previous testing has shown a variety of responses: no visible wound response (e.g., apple), phloem-based wounding gels (e.g., prunus), xylem-based clear exudates (e.g., walnut, pecan, avocado) and xylem-based dark exudates (e.g., persimmon). In this aim, Dr. Shackel will undertake a time-series, picture- and microscopy-based study of wounding responses in a variety of crops (kiwifruit, tomato, cotton, corn, melon, beans, coffee) to characterize the feasibility of monitoring water potential in each over long periods. This survey will form the basis of plans for future field testing and implementation of µTensiometers in new crops.Aim 4: Show proof of concept in field crops and improve the design accordingly (Fig. 3). After initial laboratory testing and a wounding response survey, we will validate the installation method in crops we have previously measured successfully (grape and almond), followed by testing in previously unmeasured crops (blueberry, cotton, corn).