{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,11]],"date-time":"2026-02-11T17:00:21Z","timestamp":1770829221247,"version":"3.50.1"},"reference-count":29,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2016,8,4]],"date-time":"2016-08-04T00:00:00Z","timestamp":1470268800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61574083"],"award-info":[{"award-number":["61574083"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61434001"],"award-info":[{"award-number":["61434001"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012166","name":"National Basic Research Program of China","doi-asserted-by":"publisher","award":["2015CB352101"],"award-info":[{"award-number":["2015CB352101"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"name":"National Key Project of Science and Technology","award":["2011ZX02403-002"],"award-info":[{"award-number":["2011ZX02403-002"]}]},{"name":"Special Fund for Agro-scientific Research in the Public Interest of China","award":["201303107"],"award-info":[{"award-number":["201303107"]}]},{"name":"Independent Research Program of Tsinghua University","award":["2014Z01006"],"award-info":[{"award-number":["2014Z01006"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Recently, precision agriculture has become a globally attractive topic. As one of the most important factors, the soil nutrients play an important role in estimating the development of precision agriculture. Detecting the content of nitrogen, phosphorus and potassium (NPK) elements more efficiently is one of the key issues. In this paper, a novel chip-level colorimeter was fabricated to detect the NPK elements for the first time. A light source\u2013microchannel photodetector in a sandwich structure was designed to realize on-chip detection. Compared with a commercial colorimeter, all key parts are based on MEMS (Micro-Electro-Mechanical System) technology so that the volume of this on-chip colorimeter can be minimized. Besides, less error and high precision are achieved. The cost of this colorimeter is two orders of magnitude less than that of a commercial one. All these advantages enable a low-cost and high-precision sensing operation in a monitoring network. The colorimeter developed herein has bright prospects for environmental and biological applications.<\/jats:p>","DOI":"10.3390\/s16081234","type":"journal-article","created":{"date-parts":[[2016,8,4]],"date-time":"2016-08-04T10:17:33Z","timestamp":1470305853000},"page":"1234","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["A Miniaturized On-Chip Colorimeter for Detecting NPK Elements"],"prefix":"10.3390","volume":"16","author":[{"given":"Rui-Tao","family":"Liu","sequence":"first","affiliation":[{"name":"Institute of Microelectronics, Tsinghua University, Beijing 100084, China"},{"name":"Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China"}]},{"given":"Lu-Qi","family":"Tao","sequence":"additional","affiliation":[{"name":"Institute of Microelectronics, Tsinghua University, Beijing 100084, China"},{"name":"Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China"}]},{"given":"Bo","family":"Liu","sequence":"additional","affiliation":[{"name":"Institute of Microelectronics, Tsinghua University, Beijing 100084, China"},{"name":"Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China"}]},{"given":"Xiang-Guang","family":"Tian","sequence":"additional","affiliation":[{"name":"Institute of Microelectronics, Tsinghua University, Beijing 100084, China"},{"name":"Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China"}]},{"given":"Mohammad","family":"Mohammad","sequence":"additional","affiliation":[{"name":"Institute of Microelectronics, Tsinghua University, Beijing 100084, China"},{"name":"School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan"}]},{"given":"Yi","family":"Yang","sequence":"additional","affiliation":[{"name":"Institute of Microelectronics, Tsinghua University, Beijing 100084, China"},{"name":"Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China"}]},{"given":"Tian-Ling","family":"Ren","sequence":"additional","affiliation":[{"name":"Institute of Microelectronics, Tsinghua University, Beijing 100084, China"},{"name":"Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China"}]}],"member":"1968","published-online":{"date-parts":[[2016,8,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1007\/s11119-005-0681-8","article-title":"Future directions of precision agriculture","volume":"6","author":"McBratney","year":"2005","journal-title":"Precis. 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