Wearable sensors with highly flexible and sensitive characteristics have attracted research interests in the promising field of electronic skin, health monitoring, and soft robotics. However, the developing of high-performance piezoresistive sensor is full of challenges due to the expensive equipment and complex procedures. Herein, we fabricate a reduced graphene oxide/ polyurethane composite sponge (GPCS) pressure sensor combining with dual-templates. The polyurethane (PU) sponge provides an elastic structure as solid template. Meanwhile, air bubbles as gas template are used to uniformly disperse graphene oxide (GO) sheets. The burst of air bubbles in the process of thermal treatment makes GO coating on the surface of PU skeleton, avoiding the aggregation of reduced graphene oxide. Therefore, the GPCS exhibits excellent compressibility and uniform coating structure. As a result, it also possesses high sensitivity (Gauge Factor = 3.00 in the range of 0–10% strain), fast response time (35 ms), and excellent cyclic piezoresistive stability (5000 loading–unloading cycles) when applied in the pressure sensor field. Moreover, the flexible wearable stress–strain sensor assembled by the GPCS can be easily adhered on the surface of human skin and precisely detect human movements such as elbow bending and finger bending. Such low-cost procedure and excellent sensing performance enable GPCS sensor to demonstrate tremendous application potential in the field of advanced wearable devices.

This study was conducted to determine changes in quality and microbial population of intact and fresh-cut button mushrooms (Agaricus bisporus). Freshly collected mushroom was cut into approximately 0.5 cm thick slices and washed in tap water or 100 ㎕L-1 chlorine solution (pH 7) for 60 seconds. Intact mushrooms were washed in the same condition as cut samples. Both intact and fresh-cut samples were then dried, packaged in 50㎛ poly ethylene bags, and stored at 5 ℃ for up to 9 days. Quality and microbial safety parameters such as gas composition, color, off-odor, visual quality, electrical conductivity, E. coli / coliform count, and total aerobic population were evaluated during storage. All sample packages exhibited a rapid depletion of O2 (to ~0 kPa) and accumulation of CO2 (10.3 to 12.6 kPa) throughout the storage period. No significant color difference was found between tap water and chlorine. However, chlorine treatment was effective in reducing off-odor development of intact and fresh-cut samples at the end of storage. The chlorine application also reduced aerobic bacterial populations. Both Intact and cut mushrooms had ≤ 5 log CFU/g of total aerobic plate counts until the end of storage. Fresh-cut samples regardless of chlorine sanitation had higher overall visual quality score than intact samples. Results indicated that fresh-cut mushrooms treated with chlorine maintained quality and shelf-life throughout the 9 day storage period.

This study was conducted to investigate optimum processing procedure of fresh-cut button mushrooms. The experiments were done with different processing parameters including washing method, washing time, sanitation, and cutting time. Fresh mushrooms were washed by swirling water (SW), lift type-immersion washing (LIW), or combined LIW and water spray (LI+WS). Mushroom samples were washed by LIW for 0, 1, 3, and 5 minutes separately. Mushrooms were sanitized with 0, 50, or 100 ㎕L-1 chlorine solution (pH 7) for 60 seconds. Mushrooms were sliced at different times (before washing, after washing, or after drying). The combined washing treatment, LIW+WS was effective in maintaining better appearance and higher Lightness color value among treatments. Optimum washing time to remove foreign materials and maintain color was 3 minutes when mushrooms were washed by LIW. Samples sanitized with 50 ㎕L-1 chlorine reduced initial aerobic bacterial population and had only slight residual chlorine odor. Fresh-cut mushrooms sliced after washing had the lowest loss among samples. The optimized washing, sanitation, and cutting time parameters can be used for sequential processing of fresh-cut button mushrooms.