Rapid fabrication of wearable carbon nanotube/graphite strain sensor for real-time monitoring of plant growth

Quantitative and precise measurement of plant growth is the foundation for the understanding of mechanisms that regulate the growth of plant. Plant growth is a highly dynamic process that could start/stop within seconds, but existing methods provide little information on the dynamic growth due to insufficient resolution. Here, we report on a simple manufacturing process and materials for wearable strain sensor, and a highly sensitive, automatic and real-time approach to assess the growth of plant in the range from nanometer level to centimeter level. By taking the synergistic reinforcement between graphite and carbon nanotube (CNT) membranes, a flexible, stretchable and wearable carbon nanotube/graphite sensor was obtained by simply depositing a graphite ink, a CNT ink and solidifying under ambient environment. An all-in-one device composed of the sensor and a home-made readout circuit was used to make the real-time measurement of plant growth. The monitoring of Solanum melongena L. and Cucurbita pepo captured the evidence of a rhythmic growth pattern for the fruits: the fruits grow rapidly for seconds and then rest for seconds. This approach simplified the procedure, reduced the cost, enhanced the speed, and provided nanoscale sensitivity for plant, presenting promising potentials in plant growth measurement.