Optofluidic sensing from inkjet-printed droplets: the enormous enhancement by evaporation-induced spontaneous flow on photonic crystal biosilica

Abstract

Novel transducers for detecting an ultra-small volume of an analyte solution play pivotal roles in many applications such as chemical analysis, environmental protection and biomedical diagnosis. Recent advances in optofluidics offer tremendous opportunities for analyzing miniature amounts of samples with high detection sensitivity. In this work, we demonstrate enormous enhancement factors (106–107) of the detection limit for optofluidic analysis from inkjet-printed droplets by evaporation-induced spontaneous flow on photonic crystal biosilica when compared with conventional surface-enhanced Raman scattering (SERS) sensing using the pipette dispensing technology. Our computational fluid dynamics simulation has shown a strong recirculation flow inside the 100 picoliter droplet during the evaporation process due to the thermal Marangoni effect. The combination of the evaporation-induced spontaneous flow in micron-sized droplets and the highly hydrophilic photonic crystal biosilica is capable of providing a strong convection flow to combat the reverse diffusion force, resulting in a higher concentration of the analyte molecules at the diatom surface. In the meanwhile, high density hot-spots provided by the strongly coupled plasmonic nanoparticles with photonic crystal biosilica under a 1.5 μm laser spot are verified by finite-difference time domain simulation, which is crucial for SERS sensing. Using a drop-on-demand inkjet device to dispense multiple 100 picoliter analyte droplets with pinpoint accuracy, we achieved the single molecule detection of Rhodamine 6G and label-free sensing of 4.5 × 10−17 g trinitrotoluene from only 200 nanoliter solution.

Ultra-sensitive lab-on-a-chip detection of Sudan I in food using plasmonics-enhanced diatomaceous thin film

“…The periodic pore structure of diatomite with sub-micron diameters (Figure 1a) enables guided-mode resonances (GMRs) of photonic crystals (De Stefano, et al, 2009), which is similar to the diatom biosilica as we reported previously (X. Kong, et al, 2016).…”

Advances in optoplasmonic sensors – combining optical nano/microcavities and photonic crystals with plasmonic nanostructures and nanoparticles

“…Extreme, sub-attomolar detection of a streptavidin protein was reported for nanoslot PhC nanolasers [139,[161][162][163][164][165][166][167][168], while novel PhC nanocavities combined with plasmonic nanostructures have emerged as hybrid photonic-plasmonic biosensors [169][170][171][172][173][174][175][176][177][178][179]. Unusually sensitive biodetection down to the single-molecule level with nanostructured materials comprising selfassembled silver nanoparticles on PhC diatom biosilica [180,181] and a gold antenna-in-a-nanocavity [182] substantiates the fast and steady advancement of hybrid photonic-plasmonic instrumentation utilising PhCs.…”

“…It is conceivable that these 3D metamaterials could be merged with more intricate 3D PBG cavities ( Figure 32C) to ameliorate biodetection limits [197]. A few of the latest developments in hybrid photonicplasmonic apparatuses, involving PhCs, have arrived at ascertaining single-molecule signatures [180][181][182]. Selfassembled silver nanoparticles on diatom PhC biosilica, visible in Figure 33, is a shining example [180].…”

“…A few of the latest developments in hybrid photonicplasmonic apparatuses, involving PhCs, have arrived at ascertaining single-molecule signatures [180][181][182]. Selfassembled silver nanoparticles on diatom PhC biosilica, visible in Figure 33, is a shining example [180]. SEM micrographs of a single diatom frustule ( Figure 33A and B) and the deposited silver seeds ( Figure 33D) can be seen, alongside a SERS spectrum ( Figure 33E) for 2000 droplets of 10 −16 m rhodamine 6G (cf.…”

“…SEM micrographs of a single diatom frustule ( Figure 33A and B) and the deposited silver seeds ( Figure 33D) can be seen, alongside a SERS spectrum ( Figure 33E) for 2000 droplets of 10 −16 m rhodamine 6G (cf. Figure 33C) dispensed via an inkjet printer [180].…”