This paper reports a spin-disc paper-based device with 10 individual detection units containing electromagnetic modules controlling the sample incubation time before chemiluminescence (CL) signal detection. After the sample was added to the top paper chip and incubated with the enzyme, the electromagnet was turned off to allow contact between the top and bottom paper. The H₂O₂ generated by the sample flowed vertically to the bottom paper and initiated the oxidase of the luminol to generate the CL signal. After one detection the disc was automatically rotated to the next position to repeat the above detection. The advantage of using the device over the lateral flow and the in situ detection was firstly proved using the detection of H₂O₂ and the glucose/lactate sample with 5 minute incubation. The CL intensity was increased 300 times/1000 times as the glucose/lactate was incubated for 5 minutes compared to the non-incubated samples. Afterward, the device was employed to separately detect glucose and lactate diluted in PBS, artificial sweat, artificial saliva, and fresh cell culture media. Finally, the device was employed to detect the glucose and lactate in the media collected over the 24 hour culture of PC3 cells. The uptake and production rates of glucose and lactate were correspondingly determined as 0.328 ± 0.015 pmol h⁻¹ per cell and 1.254 ± 0.053 pmol h⁻¹ per cell, respectively. The reported device has wide application potential due to its capabilities in automatic detection of multiple samples with very high sensitivity and small sample volume (down to 0.5 μL).

Micropillar array electrodes (μAEs) have been widely applied in electrochemical detection owing to their advantages of increased mass transport, lower detection limit, and potential to be miniaturized. This paper reports the fabrication, simulation, surface modification, and characterization of PDMS-based μAEs coated with gold films. The μAEs consist of 9 × 10 micropillars with a height of either 100 μm, 300 μm, or 500 μm in a 0.09 cm² region. Numerical simulation was employed to study the influence of geometrical parameters on the current density. The μAEs were fabricated by soft lithography and characterized using both SEM and cyclic voltammetry. Experiments revealed that high pillars enabled enhanced voltammetric current density regardless of the scan rates. The platinum–palladium/multi-walled carbon nanotubes (Pt–Pd/MWCNTs) were coated on the μAEs to improve their electrochemical detection capability. The μAEs demonstrated 1.5 times larger sensitivity compared with the planar electrode when hydrogen peroxide was detected. Furthermore, μAE500 with Pt–Pd/MWCNTs was employed to detect sarcosine, a potential biomarker for prostate cancer. The linear range and limit of detection for sarcosine were from 5 to 60 μM and 1.28 μM, respectively. This detection range covers the concentration of sarcosine in human tissues (0–60 μM). These results suggest that the μAEs have better detection performance in comparison to planar electrodes due to their large surface area and pillar height. This paper provides essential guidelines for the application of μAEs in high sensitivity electrochemical detection of low abundance analytes.

Homogenous mixing in microfluidic devices is often required for efficient chemical and biological reactions. Passive micromixing without external energy input has attracted much research interest. We have developed a high-performance 3D micromixer over a wide range of Reynolds number (Re) and viscosity, which was fabricated in a low-cost method of 3D printing. The characterization of the 3D printer was performed by measuring the surface roughness and fabrication error. The mixing mechanism and performance of the micromixer were investigated through numerical simulations and experiments. Influences of geometry parameters, including length, rotation direction and connection angle of helical elements, were also investigated. The mixing performance of the micromixer was studied over an ultra-wide range of flow rates from 0.3 to 70 000 μL min⁻¹ (Re = 0.01–2333.3). The mixer presented an excellent mixing performance, with a mixing efficiency of more than 96.5% for water and more than 85.1% for solutions with viscosities nearly 13 times that of water. The micromixer can achieve rapid mixing with a mixing time of 883.7 μs for aqueous solutions. In addition, the high-performance micromixer was integrated into a versatile electrochemical detection platform to enhance enzyme-catalyzed reactions. The bare microelectrode array (μEA) on the detection platform has a wide linear detection range to sarcosine from 30 to 1000 μM with a limit of detection (LOD) of 9.7 μM. The highest sensitivity for sarcosine detection (281.7 μA mM⁻¹ cm⁻²) and enhancement of current response up to 57.1% were achieved on the detection platform. This work broadens the scope of micromixer applications and sheds new light on the development of high-performance micromixers.