{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T11:10:23Z","timestamp":1785409823631,"version":"3.56.0"},"reference-count":31,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2026,6,6]],"date-time":"2026-06-06T00:00:00Z","timestamp":1780704000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100018537","name":"National Science and Technology Major Project","doi-asserted-by":"crossref","award":["2025ZD1606600"],"award-info":[{"award-number":["2025ZD1606600"]}],"id":[{"id":"10.13039\/501100018537","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["62375221"],"award-info":[{"award-number":["62375221"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"award":["62375221"],"award-info":[{"award-number":["62375221"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2024YFB4710502"],"award-info":[{"award-number":["2024YFB4710502"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012226","name":"Fundamental Research Funds for the Central Universities","doi-asserted-by":"publisher","award":["D5000240083"],"award-info":[{"award-number":["D5000240083"]}],"id":[{"id":"10.13039\/501100012226","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100021171","name":"Guangdong Basic and Applied Basic Research Foundation","doi-asserted-by":"crossref","award":["2025A1515010516"],"award-info":[{"award-number":["2025A1515010516"]}],"id":[{"id":"10.13039\/501100021171","id-type":"DOI","asserted-by":"crossref"}]},{"name":"Science Fund Program for Excellent Young Scientists"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Laser-induced breakdown spectroscopy (LIBS) offers rapid, in situ, and multi-element detection, and therefore shows strong potential for quality monitoring of metal powders in additive manufacturing. However, direct LIBS analysis of flowing metal powders is often affected by particle splashing, unstable laser\u2013particle coupling, and plasma fluctuations, which reduce signal repeatability and detection reliability. To address these issues, this study developed an integrated measurement and classification framework for identifying cross-contamination in additive-manufacturing metal powders. A stable powder particle stream was generated through vibratory feeding and particle-flow focusing, while a hollow quartz tube with a side opening was introduced to provide cylindrical spatial confinement, thereby improving the stability of laser\u2013particle interaction and enabling in situ spectral acquisition without pellet preparation. TC4 powder was used as the base material and AlSi10Mg powder as the contaminant, and samples with contamination levels of 0, 0.5, 1, 2, and 5 wt.% were prepared. Two independent batches of single-shot LIBS spectra were collected. To reduce the influence of strong spectral fluctuations, outlier spectra were removed using full-spectrum total-intensity quantile filtering, followed by asymmetric least-squares baseline correction and standard normal variate transformation. PCA combined with multiple machine-learning models was then applied for contamination identification. The results showed that LIBS spectra at different contamination levels exhibited distinguishable distributions in principal-component space, and the spectral differences between clean and contaminated powders became more pronounced with increasing contamination level. In binary classification, several models achieved high classification accuracy at medium and high contamination levels, while PCA-SVM-RBF showed the best performance at low concentrations. In five-class cross-validation, the 5 wt.% class exhibited the clearest decision boundary, whereas confusion remained among low and adjacent contamination levels, indicating that contamination-induced spectral responses followed a more continuous transition. These results demonstrate that the proposed spatially confined particle-flow LIBS framework combined with machine-learning classification can effectively achieve rapid identification of cross-contamination in additive-manufacturing metal powders and provides a feasible technical route for online powder quality monitoring.<\/jats:p>","DOI":"10.3390\/s26123591","type":"journal-article","created":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T05:43:46Z","timestamp":1780897426000},"page":"3591","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Cross-Contamination Identification of Additive Manufacturing Metal Powders Using Spatially Confined Particle-Flow LIBS and Machine Learning"],"prefix":"10.3390","volume":"26","author":[{"given":"Leiyi","family":"Ding","sequence":"first","affiliation":[{"name":"Analytical & Testing Center, School of Mechanical Engineering, Northwestern Polytechnical University, Xi\u2019an 710072, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dan","family":"Feng","sequence":"additional","affiliation":[{"name":"Analytical & Testing Center, School of Mechanical Engineering, Northwestern Polytechnical University, Xi\u2019an 710072, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yinghao","family":"Wang","sequence":"additional","affiliation":[{"name":"Analytical & Testing Center, School of Mechanical Engineering, Northwestern Polytechnical University, Xi\u2019an 710072, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mengjie","family":"Shan","sequence":"additional","affiliation":[{"name":"Analytical & Testing Center, School of Mechanical Engineering, Northwestern Polytechnical University, Xi\u2019an 710072, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9988-6790","authenticated-orcid":false,"given":"Yuanbin","family":"Wang","sequence":"additional","affiliation":[{"name":"Analytical & Testing Center, School of Mechanical Engineering, Northwestern Polytechnical University, Xi\u2019an 710072, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nan","family":"Ma","sequence":"additional","affiliation":[{"name":"Analytical & Testing Center, School of Mechanical Engineering, Northwestern Polytechnical University, Xi\u2019an 710072, China"},{"name":"Shenzhen Research Institute, Northwestern Polytechnical University, Shenzhen 518057, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Najmon, J.C., Raeisi, S., and Tovar, A. (2019). Review of Additive Manufacturing Technologies and Applications in the Aerospace Industry. Additive Manufacturing for the Aerospace Industry, Elsevier. Chapter 2.","DOI":"10.1016\/B978-0-12-814062-8.00002-9"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"110008","DOI":"10.1016\/j.matdes.2021.110008","article-title":"Metal Additive Manufacturing in Aerospace: A Review","volume":"209","author":"Gradl","year":"2021","journal-title":"Mater. Des."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Yusuf, S.M., Cutler, S., and Gao, N. (2019). Review: The Impact of Metal Additive Manufacturing on the Aerospace Industry. Metals, 9.","DOI":"10.3390\/met9121286"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"107532","DOI":"10.1016\/j.ijpe.2019.107532","article-title":"A Cost Model for the Economic Evaluation of in-Situ Monitoring Tools in Metal Additive Manufacturing","volume":"223","author":"Colosimo","year":"2020","journal-title":"Int. J. Prod. Econ."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Brand\u00e3o, A.D., Gerard, R., Gumpinger, J., Beretta, S., Makaya, A., Pambaguian, L., and Ghidini, T. (2017). Challenges in Additive Manufacturing of Space Parts: Powder Feedstock Cross-Contamination and Its Impact on End Products. Materials, 10.","DOI":"10.3390\/ma10050522"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"515","DOI":"10.1007\/s10033-017-0121-5","article-title":"Defect Formation Mechanisms in Selective Laser Melting: A Review","volume":"30","author":"Zhang","year":"2017","journal-title":"Chin. J. Mech. Eng."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"111001","DOI":"10.1115\/1.4040543","article-title":"In-Process Monitoring of Material Cross-Contamination Defects in Laser Powder Bed Fusion","volume":"140","author":"Montazeri","year":"2018","journal-title":"J. Manuf. Sci. Eng."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"113023","DOI":"10.1016\/j.matdes.2024.113023","article-title":"Ultraviolet\u2013Visible-Near InfraRed Spectroscopy for Assessing Metal Powder Cross-Contamination: A Multivariate Approach for a Quantitative Analysis","volume":"244","author":"Ceroni","year":"2024","journal-title":"Mater. Des."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Santecchia, E., Mengucci, P., Gatto, A., Bassoli, E., Defanti, S., and Barucca, G. (2019). Cross-Contamination Quantification in Powders for Additive Manufacturing: A Study on Ti-6Al-4V and Maraging Steel. Materials, 12.","DOI":"10.3390\/ma12152342"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1049\/tje2.12013","article-title":"A Technical Review of the Challenges of Powder Recycling in the Laser Powder Bed Fusion Additive Manufacturing Process","volume":"2021","author":"Soundarapandiyan","year":"2021","journal-title":"J. Eng."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"117991","DOI":"10.1016\/j.trac.2024.117991","article-title":"Laser-Induced Breakdown Spectroscopy in Space Applications: Review and Prospects","volume":"181","author":"Saeidfirozeh","year":"2024","journal-title":"TrAC Trends Anal. Chem."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Pedarnig, J.D., Trautner, S., Gr\u00fcnberger, S., Giannakaris, N., Eschlb\u00f6ck-Fuchs, S., and Hofstadler, J. (2021). Review of Element Analysis of Industrial Materials by In-Line Laser-Induced Breakdown Spectroscopy (LIBS). Appl. Sci., 11.","DOI":"10.3390\/app11199274"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1080\/05704928.2023.2187817","article-title":"Review on Laser-Induced Breakdown Spectroscopy: Methodology and Technical Developments","volume":"59","author":"Thomas","year":"2024","journal-title":"Appl. Spectrosc. Rev."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"540","DOI":"10.1039\/D0JA00437E","article-title":"Investigation of the Feasibility of Online Laser-Induced Breakdown Spectroscopy for Elemental Analysis of Compositionally Graded Alloy Parts during Their Fabrication","volume":"36","author":"Lednev","year":"2021","journal-title":"J. Anal. At. Spectrom."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"246","DOI":"10.1039\/C9JA00343F","article-title":"Online Laser-Induced Breakdown Spectroscopy for Metal-Particle Powder Flow Analysis during Additive Manufacturing","volume":"35","author":"Sdvizhenskii","year":"2020","journal-title":"J. Anal. At. Spectrom."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Schmidt, M., Huke, P., Gerhard, C., and Partes, K. (2021). In-Line Observation of Laser Cladding Processes via Atomic Emission Spectroscopy. Materials, 14.","DOI":"10.3390\/ma14164401"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1325","DOI":"10.1016\/S0584-8547(02)00048-4","article-title":"Application of Laser Plasma Confinement and Bending Effect for Direct Analysis of Powder Sample","volume":"57","author":"Suyanto","year":"2002","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"883","DOI":"10.2355\/isijinternational.ISIJINT-2021-476","article-title":"Rapid Analysis of Steel Powder for 3D Printing Using Laser-Induced Breakdown Spectroscopy","volume":"62","author":"Guo","year":"2022","journal-title":"ISIJ Int."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1129","DOI":"10.3938\/jkps.58.1129","article-title":"Direct Powder Analysis by Laser-Induced Breakdown Spectroscopy Utilizing Laser-Controlled Dust Production in a Small Chamber","volume":"58","author":"Suliyanti","year":"2011","journal-title":"J. Korean Phys. Soc."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2127","DOI":"10.1039\/C4JA00178H","article-title":"Spatially and Temporally Resolved Spectral Emission of Laser-Induced Plasmas Confined by Cylindrical Cavities","volume":"29","author":"Li","year":"2014","journal-title":"J. Anal. At. Spectrom."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1224","DOI":"10.1039\/D3JA00041A","article-title":"An Optimization Method Based on Spatial Confinement for Direct Detection of Laser-Induced Particle Flow","volume":"38","author":"Chen","year":"2023","journal-title":"J. Anal. At. Spectrom."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"146","DOI":"10.1016\/j.sab.2015.06.011","article-title":"Optimization of laser-induced breakdown spectroscopy for coal powder analysis with different particle flow diameters","volume":"110","author":"Yao","year":"2015","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_23","first-page":"200","article-title":"An Optimization Method Based on Spatial Confinement and Spectra Data Screening for Laser-Induced Breakdown Spectroscopy Quantitative Analysis of Coal Particle Flow","volume":"45","author":"Cai","year":"2024","journal-title":"At. Spectrosc."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Hao, Z., Liu, K., Lian, Q., Song, W., Hou, Z., Zhang, R., Wang, Q., Sun, C., Li, X., and Wang, Z. (2024). Machine Learning in Laser-Induced Breakdown Spectroscopy: A Review. Front. Phys., 19.","DOI":"10.1007\/s11467-024-1427-2"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1126","DOI":"10.3788\/AOS20092904.1126","article-title":"Influence of Sample Morphology on Laser Ablation Properties of Coal","volume":"29","author":"Yao","year":"2009","journal-title":"Acta Opt. Sin."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"106014","DOI":"10.1016\/j.sab.2020.106014","article-title":"Repeatability Improvement in Laser Induced Plasma Emission of Particle Flow by Aberration-Diminished Focusing","volume":"175","author":"Yao","year":"2021","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"14541","DOI":"10.1021\/acs.analchem.3c01376","article-title":"Ultrafast Laser Excitation Improves LIBS Performance for the Analysis of Optically Trapped Single Nanoparticles Owing to Characteristic Interaction Mechanisms","volume":"95","author":"Purohit","year":"2023","journal-title":"Anal. Chem."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"116859","DOI":"10.1016\/j.trac.2022.116859","article-title":"A Critical Review of Recent Trends in Sample Classification Using Laser-Induced Breakdown Spectroscopy (LIBS)","volume":"159","author":"Brunnbauer","year":"2023","journal-title":"TrAC Trends Anal. Chem."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"105872","DOI":"10.1016\/j.sab.2020.105872","article-title":"Classification of Challenging Laser-Induced Breakdown Spectroscopy Soil Sample Data\u2014EMSLIBS Contest","volume":"169","author":"Duponchel","year":"2020","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_30","unstructured":"Kramida, A., Ralchenko, Y., Reader, J., and NIST ASD Team (2024). NIST Atomic Spectra Database (Ver. 5.12) [Online]."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"665","DOI":"10.1038\/s42256-020-00257-z","article-title":"Shortcut Learning in Deep Neural Networks","volume":"2","author":"Geirhos","year":"2020","journal-title":"Nat. Mach. Intell."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/12\/3591\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T04:26:21Z","timestamp":1780979181000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/12\/3591"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6,6]]},"references-count":31,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2026,6]]}},"alternative-id":["s26123591"],"URL":"https:\/\/doi.org\/10.3390\/s26123591","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6,6]]}}}