背景:收获后水果储存和运输过程中产生的机械应力会严重影响腐烂和损失。目前,机械力的监测主要集中在集装箱和车辆受到的振动力以及影响集装箱的冲击力上。然而,内部水果之间以及水果和包装表面之间的压缩力的检测仍然不足。因此,能够感测压缩应力的适形材料是必要的。
目的:在本研究中,合成了一种三重网络增强的PSA/LiCl/CCN@AgNP导电水凝胶,用于基于机械载荷下固有阻抗的变化对水果表面的压缩力检测。
方法:就其附着力而言,对导电水凝胶进行了表征,力学,抗冻性,保水,电导率,机械力传感特性,以及监测机械力的可行性。然后,开发了一种便携式复阻抗记录仪与导电水凝胶接口,并评估了其机械力传感能力。
结果:除了其固有的导电性,水凝胶在1%至80%的应变范围内表现出显著的压力敏感性。导电水凝胶还表现出了良好的粘合性能,良好的拉伸性能(断裂伸长率为580%),相当高的抗压强度和耐久性,和长期保水能力。暴露于-20°C96小时后,水凝胶保持了它的机械强度,确认其防冻结性质。此外,开发了具有持续信号测量稳定性的便携式复阻抗记录仪,以定量获取响应于压缩力的水凝胶电阻变化。最后,验证了导电水凝胶感知苹果果实表面压缩力的有效性。
结论:导电水凝胶有望在智能包装中应用,它可以检测水果的关键机械应力,把它转换成电信号,并进一步将这些信号传输到云端,从而能够实时感测水果所经历的机械力并增强收获后的水果损失管理。
BACKGROUND: Mechanical stresses incurred during post-harvest fruit storage and transportation profoundly impact decay and losses. Currently, the monitoring of mechanical forces is primarily focused on vibrational forces experienced by containers and vehicles and impact forces affecting containers. However, the detection of compressive forces both among interior fruit and between fruit and packaging surfaces remains deficient. Hence, conformable materials capable of sensing compressive stresses are necessary.
OBJECTIVE: In the present study, a triple-network-reinforced PSA/LiCl/CCN@AgNP conductive hydrogel was synthesized for compression force detection on fruit surfaces based on changes in intrinsic impedance under mechanical loading.
METHODS: The conductive hydrogel was characterized in terms of its adhesion, mechanics, frost resistance, water retention, conductivity, mechanical force-sensing properties, and feasibility for monitoring mechanical forces. Then, a portable complex impedance recorder was developed to interface with the conductive hydrogel and its mechanical force sensing ability was evaluated.
RESULTS: Beyond its inherent conductivity, the hydrogel exhibited notable pressure sensitivity within the strain range of 1 % to 80 %. The conductive hydrogel also demonstrated a commendable adhesion property, favorable tensile property (580 % elongation at break), substantial compressive strength and durability, and a long-term water retention capability. After exposure to -20 °C for 96 h, the hydrogel maintained its mechanical strength, affirming its anti-freezing property. In addition, a portable complex impedance recorder with sustained signal measurement stability was developed to quantitatively acquire the hydrogel resistance changes in response to compression forces. Finally, the effectiveness of the conductive hydrogel for sensing compression force on the surface of apple fruits was validated.
CONCLUSIONS: The conductive hydrogel holds promise for applications in smart packaging, wherein it can detect crucial mechanical stress on fruit, convert it into electrical signals, and further transmit these signals to the cloud, thereby enabling the real-time sensing of mechanical forces experienced by fruits and enhancing post-harvest fruit loss management.