Ball pen writing-without-ink: a truly simple and accessible method for sensitivity enhancement in lateral flow assays

Lateral flow assays (LFAs), a popular point-of-care testing platform, have found widespread applications from laboratory to clinics. However, LFA-based testing is still subject to limited detection sensitivity, especially for classical gold nanoparticle-based LFAs. Inspired by traditional pen-based writing technologies, we developed a ball pen writing-without-ink method to amplify the detection signal of LFAs through controlling fluid flow rate. An enhancement of detection sensitivity by two times was obtained. Since the underlying mechanism of this method to improve detection sensitivity is to control the flow rate of the liquid on paper, it may be suitable for most paper-based platforms.