Lab-on-tip based on photothermal microbubble generation for concentration detection

Lab-on-fiber is an emerging technology using compact fiber microstructures smaller than their lab-on-a-chip counterparts. In this paper, we report a lab-on-tip (LoT) technology for concentration detection based on a photothermal gas microbubble, which is generated by locally heating the fiber tip with a gold nanofilm. The temporal growth process of the microbubble is repeatable, and the parametric influence is investigated. The diameter of the microbubble is monitored by imaging, and its increment is detected as a function of concentration. The reflection spectrum of the microbubble as a micro-interferometer is recorded and the free spectral range (FSR) can also be used for concentration detection. Solutions of sucrose and hydrogen peroxide are used as examples to evaluate sensing performance. For sucrose detection, a dynamic range of 0.5 wt% to 50 wt% is obtained. For hydrogen peroxide detection, an unprecedented dynamic range of 5 orders of magnitude, 10−5 M ∼ 1 M, is achieved. The demonstrated performance is exceptional and the method is simple and cost effective.