We present a novel electrokinetic stacking (ES) method based on field amplification on a simple paper device for sample preconcentration. With voltage application, charged probe ions in a solution of lower conductivity stack and form a narrow band at the boundary between the sample and the background electrolyte of higher conductivity. The stacking band appears quickly and stabilizes in a few minutes. With this ES method, three orders of magnitude signal improvement was successfully achieved for both a fluorescein probe and a double-stranded DNA within 300 s. This enhanced stacking efficiency is attributed to a focusing effect due to the balance between electromigration and counter electroosmotic flow. We also applied this ES method to other low-cost fiber substrates such as cloth and thread. Such a simple and highly efficient ES method will find wide applications in the development of sensitive paper-based analytical devices (PADs), especially for low-cost point-of-care testing (POCT).
Cool linen is used to produce summer clothing to be known as summer cloth. Nevertheless, ramie-fiber surfaces bear hydrophilic hydroxyls to result in rainwater wetting and stain adhering. To achieve outdoor application of summer cloth, here, light all-organic hydrophobic copolymer coatings were formed on surfaces of two various summer clothes. First, atom transfer radical polymerization was utilized to synthesize polydimethylsiloxane-block-polymethacryloxypropyl trimethoxysilane. Then, neat copolymer films and copolymer coating/cloth complexes were prepared. Coating/cloth complexes were characterized. Finally, hydrophobicity-induced antifouling properties of complexes were confirmed, followed by justifying good resistance to surface abrasion for coating/compact summer cloth complex with superhydrophobicity. As a result, the optimal coating/compact summer cloth complex can fight against ink pollution and exhibit a water contact angle of 150.3 degrees after 200 abrasion cycles, in which neat copolymer film has a light transmittance of ~ 90% based on 30 min of pre-hydrolysis. Superhydrophobicity is ascribed to silicon surface enriching-induced low surface energy as well as surface micro-/nano-binary composite rough structure. This work has realized a controllable preparation of silicon-bearing copolymers with long-term hydrophobicity for protecting various summer clothes.
Cloth fabrics and smartphones have become the two things people are most familiar with. Particularly, smartphones are used as portable personal computers, revolutionizing communication and lifestyle. Here, screen-printing technology is applied to fabricate carbon electrodes and electrochemical chambers on a single hydrophilic cloth, while the cloth-based electrochemiluminescence (ECL) signals are read out by using an inexpensive smartphone. Therefore, the ECL detection is available in both low-cost disposable sensors and a portable format, which may be very suitable to be used as a non-invasive monitoring tool for medical diagnostics. As a proof-of-principle, lactate oxidase is immobilized onto the working electrode for the lactate measurement. Under optimized conditions, the lactate levels can be quantified over the range of 0.05–2.5 mM, with a detection limit of 0.035 mM and the relative standard deviations of 4.7%, 5.2% and 5.0% for 0.05, 0.5 and 2.5 mM lactate (n = 5). In addition, the proposed biosensor has an acceptable stability and selectivity. Finally, the ECL biosensor is successfully applied for the determination of lactate in human saliva. These results show that the presented ECL platform has the potential to be applied to non-invasively detect a variety of analytes of medical interest.
危险品化学品经营许可证（带存储）