Origami chips: Development and validation of a paper-based Lab-on-a-Chip device for the rapid and cost-effective detection of 4-methylmethcathinone (mephedrone) and its metabolite, 4-methylephedrine in urine

•Mephedrone, a synthetic cathinone, is a widely used new psychoactive substance.•We present a Lab-on-a-Chip to detect mephedrone at clinically relevant levels.•Cross-reactivity with common adulterants, stability and reproducibility were examined.•Using a Lab-on-a-Chip enables rapid (<3 min), low-cost, on-site detection.