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Most biosensors employ small sample quantities (less than 100 μL) for bacteria detection, thereby resulting in inaccurate low-concentration measurements. Detection performed using small sample volumes with low bacteria concentration may produce false-negative results. Therefore, sample pretreatment plays a critical role in accurate bacteria detection. This paper presents an impedimetric bacteria-detection sensor integrated with bacteria concentration and separation devices for rapid bacteria detection. Post conjugation using magnetic particles (MPs), the MP-conjugated bacteria (MP/Bac) are concentrated via magnetophoresis by a factor exceeding 100. In addition, MP/Bac are separated from MPs via dielectrophoresis to prevent occurrence of signal errors caused by MPs not conjugated with bacteria. Subsequently, concentrated MP/Bac are captured on a sensor electrode, and bacteria concentration is detected by measuring signal changes caused by the impedance difference between bacteria and the medium. The performance of the proposed bacteria-detection device was evaluated using a 5-mL homogenized cabbage sample injected with Staphylococcus aureus at 30 mL/h flow rate. The observed signal change was measured for 10 min using a sample with a concentration of 5–5 × 103 CFU/mL and was found to be approximately 0.34 mV at 50 CFU/mL; the limit of detection was 36 CFU/mL. These results confirm that the proposed device can detect low bacteria concentrations in food samples.

Rapid, sensitive and accurate point-of-care-testing (POCT) of bacterial load from a variety of samples can help prevent human infections caused by pathogenic bacteria and mitigate their spreading. However, there is an unmet demand for a POCT device that can detect extremely low concentrations of bacteria in raw samples. Herein, we introduce the ‘count-on-a-cartridge’ (COC) platform for quantitation of the food-borne pathogenic bacteria Staphylococcus aureus. The system comprised of magnetic concentrator, sensing cartridge and fluorescent image reader with a built-in counting algorithm facilitated fluorescent microscopic bacterial enumeration in user-convenient manner with high sensitivity and accuracy within a couple of hours. The analytical performance of this assay is comparable to that of a standard plate count. The COC assay shows a sensitivity of 92.9% and specificity of 100% performed according to global microbiological criteria for S. aureus which is acceptable below 100 CFU/g in the food matrix. This culture-independent, rapid, ultrasensitive and highly accurate COC assay has great potential for places where prompt bacteria surveillance is in high demand.

Most biosensors use small amounts (a few tens of microliters) of a sample to detect bacteria. However, it is necessary to detect bacteria with at least a few milliliters of the sample to obtain statistically significant results. Therefore, the bacteria concentration process is critical for the rapid and accurate detection of bacteria. In addition, most bacteria concentration devices have a low throughput (200 μL/h–3.6 mL/h), and it takes several hours to process a few milliliters of a sample. To significantly improve the throughput, a magnetophoresis-based bacteria concentration device is developed using a commercial polyethylene tube. The device is fabricated in three dimensions by wrapping the tube around the magnet. The channel length of the proposed device can be easily adjusted by adopting different tube lengths. Thus, particles can be concentrated even under high flow rates. The optimum channel length is calculated using the particle velocity engendered by the magnet and experimentally evaluated under various channel lengths and flow rate conditions. Moreover, the performance of the proposed device is evaluated using two different food samples, milk and homogenized cabbage, into which bacteria are spiked. The separation efficiency and concentration factor are higher than 92% and 110 times, respectively, at a flow rate of 40 mL/h. These results confirm that the proposed device has a considerably high throughput in comparison with that presented in previous studies.

While sensors that allow for high-throughput enumeration of microorganisms within drinking water are useful for water quality monitoring, it is particularly challenging to accurately quantify microorganisms that are present in low numbers (

Pressure measurement is considered one of the key parameters in microfluidic systems. It has been widely used in various fields, such as in biology and biomedical fields. The electrical measurement method is the most widely investigated, however, it is unsuitable for microfluidic systems because of a complicated fabrication process and difficult integration. Moreover, it is generally damaged by large deflection. This paper proposes a thin-film-based pressure sensor that is free from these limitations, using a liquid metal called galinstan. The proposed pressure sensor is easily integrated into a microfluidic system using soft lithography because galinstan exists in a liquid phase at room temperature. We investigated the characteristics of the proposed pressure sensor by calibrating for a pressure range from 0 to 230 kPa (R2 &gt, 0.98) using deionized water. Furthermore, the viscosity of various fluid samples was measured for a shear-rate range of 30–1000 s−1. The results of Newtonian and non-Newtonian fluids were evaluated using a commercial viscometer and normalized difference was found to be less than 5.1% and 7.0%, respectively. The galinstan-based pressure sensor can be used in various microfluidic systems for long-term monitoring with high linearity, repeatability, and long-term stability.