Micro-coffee-ring-patterned fiber SERS probes and their in situ detection application in complex liquid environments

•Micro-coffee-ring patterns are fabricated on fiber facet using a self-developed laser-induced dynamic dip-coating method.•The formation mechanisms of micro-coffee-rings on fiber facet are analyzed.•These fiber SERS probes simultaneously show high detection sensitivity and good reproducibility in SERS detections.•In situ trace SERS detections in complex liquids, e.g. pesticide residues in juice and antibiotics in milk, are achieved.