Piezoresistive composite-based flexible pressure sensors often suffer from a trade-off between the sensitivity and measurement range. Moreover, the sensitivity or measurement range is theoretically limited owing to the negative piezoresistive coefficient, resulting in resistance variation below 100%. Here, flexible pressure sensors were fabricated using the three-dimensional (3D) printing technique to improve both the sensitivity and sensing range through the positive piezoresistive effect. With the addition of carbon nanotubes (CNTs) and fumed silica nanoparticles (SiNPs) as a conductive filler and rheology modifier, respectively, the viscoelastic silicone rubber solution converted to a printable gel ink. Soft and porous composites (SPCs) were then directly printed in air at room temperature. The sensitivity and sensing range of the SPC-based pressure sensor can be simultaneously tuned by adjusting the conducting CNT and insulating SiNP contents. By optimizing the density of the CNT conductive network in the matrix, positive piezoresistive sensitivity (+0.096 kPa–1) and a large linear sensing range (0–175 kPa) were obtained. To demonstrate potential applications, the completely soft SPC-based sensor was successfully used in grasp sensing and gait monitoring systems. The 3D printed sensors were also assembled as a smart artificial sensory array to map the pressure distribution.
Droplet microfluidics is a rapidly advancing area of microfluidic technology, which offers numerous advantages for cell analysis, such as isolation and accumulation of signals, by confining cells within droplets. However, controlling cell numbers in droplets is challenging due to the uncertainty of random encapsulation which result in many empty droplets. Therefore, more precise control techniques are needed to achieve efficient encapsulation of cells within droplets. Here, an innovative microfluidic droplet manipulation platform had been developed, which employed positive pressure as a stable and controllable driving force for manipulating fluid within chips. The air cylinder, electro-pneumatics proportional valve, and the microfluidic chip were connected through a capillary, which enabled the formation of a fluid wall by creating a difference in hydrodynamic resistance between two fluid streams at the channel junction. Lowering the pressure of the driving oil phase eliminates hydrodynamic resistance and breaks the fluid wall. Regulating the duration of the fluid wall breakage controls the volume of the introduced fluid. Several important droplet microfluidic manipulations were demonstrated on this microfluidic platform, such as sorting of cells/droplets, sorting of droplets co-encapsulated cells and hydrogels, and active generation of droplets encapsulated with cells in a responsive manner. The simple, on-demand microfluidic platform was featured with high stability, good controllability, and compatibility with other droplet microfluidic technologies. Graphical abstract
Zhihan Cai,Wangzhe Xia,Haibo Li,Rui Qin,Fangping Wu,Jianhong Wu,Xianze Yin,Zehao Li,Yongsheng Yang
Water pollution is a critical global environmental challenge, necessitating efficient and innovative remediation strategies. This work outlines the successful synthesis of poly(vinylidene fluoride) (PVDF) composite membranes infused with varying proportions of magnesium-doped zinc oxide (MgZnO) using an economical and simplified interfacial film-forming method. The MgZnO0.1PVDF1–1 composite membrane demonstrates exceptional and stable purification performance, significantly reducing the amount of antibiotics in water through a combination of static adsorption and ultrasound-guided piezoelectric degradation. SEM/FTIR/XPS/BET analyses postulate the underlying adsorption mechanisms as surface complexation, ion-dipole interaction, and cation exchange coupled with piezoelectric catalysis via the ion-dipole moment effect. The degradation process leverages a unique converse and positive piezoelectric effect, inducing surface mechanical deformation and internal free radical polarization and fostering outstanding tetracycline (TC) degradation. Comprehensive experiments considering variables such as pH, concentration, and reaction time further substantiate the superior performance of MgZnO0.1PVDF1–1, achieving an impressive maximum TC removal ratio of 86%. The high TC removal efficiency, enduring recycle performance, and economical operative method underline MgZnO0.1PVDF1–1 as a significant potential for mitigating antibiotic water pollution.
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