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.学界普遍通过叶片叶绿素含量推断植物健康状态与营养状况。本研究开发了一款可搭载于智能手机的3D打印配件，可实现6种植物的叶片叶绿素浓度估算，并公开了该配件的3D打印文件与组装细节，方便使用者在任意地点自行制备。该系统借助智能手机的环境光传感器，测量663nm波段LED光线穿透完整植物叶片后的透射率；该波段光线可被叶绿素吸收，以此实现叶绿素浓度的定量检测。通过与标准分光光度计的测量结果进行校准，可获取叶绿素含量的绝对数值。本研究通过将该配件的检测结果与通用分光光度法及标准SPAD 502™便携式叶绿素仪的测量结果进行对比，完成了性能验证。这款与智能手机连接的系统由3D打印机身、照明电路与通用备件组成，其叶绿素检测性能可与广泛使用的标准系统相媲美。鉴于叶绿素浓度与植物营养状态间的关联已被广泛研究，且当前智能手机普遍搭载各类传感器，该智能手机配件的优化与推广将有助于推动精准农业与数字农艺技术在不同农业规模场景中的普及应用。