Abstract. Ultrasonic waves, either bulk waves or guided waves, are commonly used for non-destructive evaluation, for example in structural health monitoring. Traditional sensors for detecting ultrasonic waves include metallic strain gauges and piezoelectric ceramics. Recently piezoresistive nanocomposites have emerged as a promising sensor with high sensing range. In this paper, a constriction-resistive based sensor made from a graphene reinforced PLA filament is developed using a fused deposition modelling 3D printing approach as a novel type of ultrasonic sensor for structural health monitoring purposes. The sensor is made of very low-cost and recyclable thermoplastic material, which is lightweight and can be either directly printed onto the surface of various engineering structures, or embedded into the interior of a structure via fused filament fabrication 3D printing. These characteristics make this sensor a promising candidate compared to the traditional sensors in detecting ultrasonic waves for structural health monitoring. The printed sensors can detect ultrasonic signals with frequencies around 200 kHz, with good signal-to-noise ratio and sensitivity. When deployed between two adjacent printed tracks , and exploiting a novel kissing-bond mechanism, the sensor is capable of detecting ultrasonic waves. Several confirmatory experiments were carried out on this printed sensor to validate the capability of the printed sensor for structural health monitoring.

Artificial pollination methods rely primarily on air-jets, vibrating wands and trellis tapping which can spread pathogens. This problem can be addressed by non-contact sonic techniques that vibrate cells via sound waves yet how frequency and intensity affect pollination, seed set and fruit size remain unclear. Our study systematic characterizes frequency-dependent vibration events on greenhouse-grown tomato flowers comparing them with contact-induced oscillations from a vibrating wand and a mechanical shaker arm. Sonic vibrations in the frequency range from 50 to 10,000 Hz increased pollination, fruit size, weight, and seed set in Sweetelle and Endeavour commercial varieties. Scanning electron microscopy revealed sonication loosened the trichomes joining the poricidal cone lobes that encase the anthers filled with pollen. Ultra-sonic frequencies enlarged fruit size, whereas seed set remained constant thereby challenging the floral cells power-law rheological characteristics in different frequency scales. Our bioacoustics non-contact precision technology can be used to boost tomato floral self-pollination. Teaser Leveraging bioacoustics from bees and bats to boost precision pollination of tomato flowers and fruit size in commercial varieties