Droplet Enhanced Fluorescence for Ultrasensitive Detection Using Inkjet

Abstract

A fluorescence enhanced phenomenon was found within a micrometer-sized liquid droplet, and it was adopted to construct droplet enhanced fluorescence (DEF) for ultrasensitive fluorescence detection. In this paper, an inkjet was utilized to eject perfect spherical droplets to construct a microspherical resonator and to develop a DEF system. It was utilized to implement ultrasensitive fluorescence detection in a liquid specimen with a volume of several microliters. The DEF detection of fluorescent molecules, fluorescein sodium, was used as a model to validate the proposed enhanced fluorescence detection method. A low limit of detection (LOD) for fluorescein sodium of 124 pM was obtained. The sensitive detection of single stranded DNA (ssDNA) was experimentally completed, with a wide range of linearity with a LOD of 312 pM. The proposed mechanism can be used as an ultrasensitive detection technique for analyzing microliters of liquid samples.

Ball-lens assisted sensitivity improvement of fluorescence immunoassay in microchannels

“…The BFE effect might be attributed to three aspects: (1) the microbead focused the exciting light and improved the excitation efficiency; 32 (2) the microbead focused the emitted fluorescence and enhanced the local intensity; (3) the microbead improved the fluorescence collection efficiency, especially at high incidence angles, and increased the effective NA of the objective. 33 To verify the BFE effect was really existed or a false phenomenon caused by inappropriate focusing of the objective lens, we investigated the objective lens focusing process (Fig. S2, ESI † ).…”

Viscosity-Mediated Growth and Coalescence of Surface Nanodroplets

“…In previous reports, it has been shown that droplets can focus light to enhance the fluorescence intensity and enable more sensitive detection. 5,32 The smaller droplets in our experiments have higher curvature so they can have stronger focusing effect for the emitted light from the fluorescence molecules. Such optical effect may find applications in chemical analysis, as fluorescence signal is widely used in sensing and biomedical analysis, for example the product from polymerase chain reaction in identification of nucleic acid sequence.…”

“…Surface nanodroplets have attracted significant research interest, due to various applications for micropatterning, 1 optical lenses, 2,3 chemical and biological analysis, 4,5 and crystallization. 6 Tuning the size distribution of droplets is important for droplet-based sensing, 7 biochemical assays, 8 miniaturized substrates for cell culture, 9 fabrication of nanostructures from ionic liquids, 10 and many others.…”

Encapsulated Nanodroplets for Enhanced Fluorescence Detection by Nano‐Extraction

“…The LoD of FR at 50 p m is 2–3 times lower than that determined by the recently reported method using ink‐jet printed microdroplets. [ 33 ] The 60‐fold enhancement of fluorescence is also 6–20 times higher than that for reported methods using micro‐reflectors, [ 25 ] micro‐lens arrays, [ 32 ] plasmonic thin metal film, [ 27 ] and immobilized quantum dots. [ 31 ] Moreover, in comparison with methods of generating well‐designed photonic crystals or nanopatterned materials which can lead to 76–108‐fold fluorescence enhancement, [ 28,44 ] our method shows comparable performance but in a simple, low‐cost, and highly efficient manner.…”

“…[ 31 ] Most of these approaches require precisely designed nanostructures and the molecules to be in the optical near‐field of the enhancing surface. The recent use of liquid‐based micro‐objects to enhance fluorescence collection, such as by micro‐reflectors or microspherical resonators, [ 18,25,32,33 ] promises simple, efficient sensitive and cost‐effective fluorescence detection. These studies are still limited, and further improvement in fluorescence enhancement for the direct quantification of trace analytes is required.…”