The development of rapid and sensitive point-of-test devices for on-site monitoring of heavy-metal contamination has great scientific and technological importance. However, developing fast, inexpensive, and sensitive microarray sensors to achieve such a goal remains challenging. In this work, we present a DNA-nanostructured microarray (DNM) with a tubular three-dimensional sensing surface and an ordered nanotopography. This microarray enables enhanced molecular interaction toward the rapid and sensitive multiplex detection of heavy-metal ions. In our design, the use of DNA tetrahedral-structured probes engineers the sensing interface with spatially resolved and density-tunable sensing spots that improve the microconfined molecular recognition. A bubble-mediated shuttle reaction was used inside the DNM-functionalized microchannel to improve the target-capturing efficiency. Using this novel DNM biosensor, the sensitive and selective detection of multiple heavy-metal ions (i.e., Hg2+, Ag+, and Pb2+) was achieved within 5 min, the detection limit was down to 10, 10, and 20 nM for Hg2+, Ag+, and Pb2+, respectively. The feasibility of our DNM sensor was further demonstrated by probing heavy-metal ions in real water samples with a direct optical readout. Beyond metal ions, this unique DNM sensor can easily be extended to in vitro bioassays and clinical diagnostics.Keywords: DNA nanostructures; metal ions; microarray; microchannel; multiplex detection;

The fluidic control method is a fundamental technology for the development of nanofluidics. In this report, an organic phase was driven to flow inside the nanochannel because of its dissolution into an aqueous phase. With selective modification, a stable organic/aqueous interface was generated at the junction of the micro/nanochannels in a hybrid chip. The aqueous phase was kept flowing in the microchannel, and the organic phase in the nanochannel dissolved into the aqueous phase through the interface and produced a flow inside the nanochannel. This method is simple, easy to control and requires no specific equipment. Importantly, the flow is driven by the surface tension in a controllable manner, which will not be affected by the depth of the nanochannel. This method can be a useful alternative to the present fluidic control methods in nanofluidics.

Microarray technology is a useful tool for nucleic acid detection and has been widely used in biology and related research fields. However, the procedure is labor intensive and time consuming. Microfluidic chip-based microarrays save time with better performance, but the low spot density and probe number limit its applications. To develop high performance microarrays with high spot density within a microchannel, a method is reported here for preparing microarrays in a capillary by generating probe droplet arrays. The probes in droplets are immobilized onto the inner wall of the capillary to form a one-dimensional probe array, and then a sample solution is introduced to hybridize with the probe array. The effect of the capillary's inner diameter was evaluated to realize a high-density probe array. The processes of array generation and probe immobilization were studied to avoid possible cross contamination. The background from probe immobilization during the array generation and incubation was quantified to assure sensitivity. Multiple sample detection was also demonstrated within one capillary. The capillary based microarray assay had high spot density, easy fabrication, fast detection, high sensitivity and multiple sample capacity.Highlights► High-density probe array containing different probes was prepared along the microchannel. ► Fast hybridization and sensitive detection were realized inside the capillary. ► The array developed here also provided the capacity for detection of multiple samples.