A 3D-Printable smartphone accessory for plant leaf chlorophyll measurement
Plant health and nutrition are universally inferred from leaf chlorophyll content. This research developed a 3D-printed accessory which attaches to a smartphone and estimates the concentration of chlorophyll in the leaves of six plant species. It unveils the 3D printing files and assembling details to allow the accessory to be built anywhere. The system uses a smartphone's ambient light sensor to measure the transmission of a 663 nm LED band through intact plant leaves. This band of light is absorbed by chlorophyll and allows its concentration to be measured. Absolute values of chlorophyll content are obtained by calibration against standard spectrophotometer measurements. This accessory is tested by comparing its readings to the universal spectrophotometric method and compared to a standard SPAD 502™ portable meter. This smartphone-connected system that has a 3D-printed body, lighting circuit, and common spare parts, measures chlorophyll in a way comparable to universally used standard systems. Due to the well-studied relationship between chlorophyll concentration and nutritional status of plants, and due to the ubiquitous presence of other sensors in smartphones today, the improvement and adoption of this smartphone accessory would ease the spread of precision farming and digital agronomy practices throughout the different scales of agriculture.