In this study, a newly fluorescent ZnSe quantum dots (QDs) with ion imprinting technology was firstly realized on the three-dimensional (3D) rotary paper-based microfluidic chip platform which can be used to realize specific and multiplexed detection of Cadmium ions (Cd 2+ ) and Lead ions (Pb 2+ ). Compared to CdTe quantum dots, ZnSe quantum dots are less toxic and more environmental friendly. In addition, this design improved the portability of the device by transferred the liquid phase of ZnSe QDs@ion imprinted polymers to solid glass fiber paper. Moreover, the 3D rotary microfluidic chip (μPADs) showed great advantages including low cost, simple and fast facile operation, multiplexed detection, and showed good sensitivity and selectivity. Under optimal experiment conditions, our proposed method was enabled to realize specific and multi-channel determination of Cd 2+ and Pb 2+ ions. The developed sensor of Cd 2+ μPADs provided a linear response from 1 to 70 μg/L with a lower detection limit of 0.245 μg/L, and Pb 2+ μPADs provided a linear response from 1 to 60 μg/L with a lower detection limit of 0.335 μg/L, respectively. Excitingly, this newly designed 3D rotary μPADs exhibited quantitative information conveniently, which showed the promising application prospects to rapid testing target metal ions in environmental in the future.

A novel strategy for fabricating the paper-based valves on microfluidic paper-based analytical devices (μPADs) was described to control fluid in a user-friendly way. Initial prototypes of 3D μPADs manipulate the spatial distribution of fluid within the device. The movable paper channel in a different layer could be achieved using the channel's connection or disconnection to realize the valve function using plastic comb binding spines (PCBS). The entire valve manipulation process was similar to a desk calendar that can be flipped over and turned back. It is notable that this kind of PCBS valve can control a fluid in a simple and easy way without the timing setting or any trigger, and this advantage makes it user-friendly for untrained users to carry out the complex and high throughput operations. The reusable plastic comb binding spines greatly reduce the cost of fabricating paper-based valves. To evaluate the performance, the actual samples of Fe (II) and nitrite were successfully analyzed. We hope this method will introduce a new approach to fabrication of paper-based valves on μPADs in the future.