Effective and reliable interconnections are crucial for microfluidics to connect with the macro world. Current microfluidic interfaces are still bulky, expensive, or with issues of clogging and material limitation. In this study, a novel ultraviolet (UV)-assisted coaxial three-dimensional (3D) printing approach was proposed to fabricate hollow microfluidic connectors with advantages of rapid prototyping, fixture-free, and materials compatible. An assembled coaxial nozzle was designed to enable co-flow extrusion, where the inner flow (water) served as the sacrificial layer and the outer flow (adhesive) was cured for shell formation. Furthermore, a converged UV-LED light source was attached to the coaxial nozzle for UV curing of adhesives. UV rheological characterizations were performed to study the UV curing kinematics, and the gelation time was employed to describe the state transition behaviors of UV curable adhesives used in the study. To explore requirements for successful hollow connectors direct printing, processing criteria such as co-flow regime and pre-cure time were investigated. The hollow connectors with an inner channel diameter of ~150 $\mathsf{\mu }$ m and a height of 5 mm were successfully printed on polymethyl methacrylate (PMMA) and glass substrate. The integration feasibility of the proposed method was also demonstrated by the presented microfluidic device with printed hollow connectors.

3D printing is regarded as a useful tool for the fabrication of microfluidic connectors to overcome the challenges of time consumption, clogging, poor alignment and bulky fixtures existing for current interconnections. 3D-printed connectors without any additional components can be directly printed to substrate with an orifice by UV-assisted coaxial printing. This paper further characterized and evaluated 3D-printed connectors fabricated by the proposed method. A process window with an operable combination of flow rates was identified. The outer flow rate could control the inner channel dimensions of 3D-printed connectors, which were expected to achieve less geometric mismatch of flow paths in microfluidic interfaces. The achieved smallest inner channel diameter was around 120 µm. Furthermore, the withstood pressure of 3D-printed connectors was evaluated to exceed 450 kPa, which could enable microfluidic chips to work at normal pressure.

Anti-counterfeiting technologies of banknotes are essential to avoid financial fraud and maintain the stability of the socio-economic system. In recent years, the technologies used by counterfeiters have become more and more advanced, bringing great challenges to traditional methods of authenticity check. Therefore, the identification technologies of banknotes urgently need to be improved. Terahertz spectroscopy is widely used for analysis and material identification due to its properties (such as biomolecular fingerprinting spectrum, ultra-weak photon emission, non-destructive and time-resolution detection). In this paper, we apply the transmission terahertz imaging to the identification of anti-counterfeit labels of RMB. We designed and built a THz-TDS confocal imaging system, which has higher image resolution than traditional THz-TDS imaging systems. We used this system to perform terahertz imaging on anti-counterfeit labels of banknotes. The results show that our designed and built THz-TDS confocal imaging system not only provides higher image quality, but also can identify more details of the anti-counterfeit labels of banknotes.

A closet featured with 1 minute disinfection time was developed for high efficient disinfection of protective coats. An ultraviolet-C light-emitting diode (UVC LED) module with uniform irradiance was developed in a previous study. 56 UVC LED modules were installed in the closet to achieve 99.99% disinfection rate of E. coli, S. aureus and Pseudomonas aeruginosa, 99.9% disinfection rate of H1N1, and at least 99.5% disinfection rate of EV71 in 1 minute. During burn-in tests, the closet remained stable in 1 minute working cycle in terms of thermal and optical characteristics. UVC treated protective coats, e.g., disposable medical protective coveralls, were assessed based on bacterial filtration efficiency and viral filtration efficiency. It was concluded that there was no significant degradation for disposable medical protective coveralls after UVC exposure for 60 minutes, indicating that the protective capability of medical protective coveralls did not degrade after 60 disinfection cycles in the UVC LED disinfection closet. The closet offers an effective solution for reuse of protective coats.

Microfluidics has attracted significant attention for biological applications, particularly for high-throughput screening and multiplexing. However, conventional interconnect techniques are limited in their ability to fabricate the hundreds or thousands of microfluidic interconnects needed to process multiple samples for high-throughput microfluidics. To address this challenge, coaxial printing was invented to enable rapid, customizable, and scalable microfluidic interconnects. This paper focuses on the assembly process of coaxial printed interconnects for immobilized protein microfluidic assays. We demonstrate the immobilization of protein into a 1 x 1 microwell microfluidic unit with printed connectors to showcase the process.