Jiahua Zhong

Extracting tomato juice for maturity assessment is critical for ensuring a timely harvest. Nevertheless, the limitations of existing sampling tools and heavy reliance on manual operation may result in tomatoes being harvested outside their optimal window, resulting in economic losses. Therefore, there is an urgent need for a better method for tomato juice sampling and maturity monitoring. In this work, an unmanned aerial vehicle (UAV)-mediated directional sampling system (uDSS) was developed for tomato identification in the field and the collection of tomato juice. The system integrates a UAV with a real-time ultra-wideband (UWB) positioning system. The system autonomously performs the flight and juice-sampling sequence; juice recovery and Brix measurement are carried out after the flight. With regard to the sampling procedure, a 3D-printed microneedle (MN) with porous synthetic paper for capillary liquid absorption was employed to penetrate the tomato and extract juice. Lastly, the sugar content of tomatoes was measured in order to verify the feasibility of uDSS. This unmanned system is expected to promote the development of UAV-based solutions in precision agriculture and intelligent food industry.

Paper-based microfluidic devices (μPADs) have attracted significant attention for point-of-care testing (POCT), environmental monitoring, and food safety due to their low cost, ease of use, and minimal instrument dependence. However, fabricating high-resolution and reproducible microchannels on paper remains challenging. Conventional methods such as wax printing, photolithography, and inkjet printing are limited by resolution or equipment cost. Here, we present a low-cost, high-resolution fabrication method for μPADs, termed wax soft lithography, which combines wax printing with soft lithography. Through this method, microchannels with a minimum width of 234 ± 62 μm were consistently produced, and complex patterns were successfully fabricated, demonstrating high precision and reproducibility. As a proof-of-concept demonstration of device functionality, the fabricated μPADs were used to detect glucose in spiked urine samples, showing a concentration-dependent colorimetric response. This method provides an effective route for rapid production of high-resolution μPADs in resource-limited settings. With further validation before practical applications, this method shows promise for future development in POCT.

This work presents a novel microfabrication process that addresses the interference of thiol groups on off-stoichiometry thiolene (OSTE) surfaces with the curing of polydimethylsiloxane (PDMS) by integrating the high-performance polymer Parylene-C. The process utilizes a Parylene-C coating to encapsulate the active thiol groups on the OSTE surface, enabling precise replication of PDMS microstructures. Based on this method, PDMS micropillar arrays and microwell arrays were successfully fabricated and applied in passive plasma separation and polymorphic crystal formation, respectively. The experimental results demonstrate that the plasma-separation chip efficiently isolates plasma from whole-blood samples with varying hematocrit (HCT) levels, achieving a separation efficiency of up to 57.5%. Additionally, the microwell array chip exhibits excellent stability and controllability in the growth of salt and protein crystals. This study not only provides a new approach for microfabricating microfluidic chips, but also highlights its potential applications in biomedical diagnostics and materials science.