Zwitterionic materials have received great attention because of the non-fouling property. As a result of the electric neutrality of zwitterionic polymers, their layer-by-layer (LBL) assembly is generally conducted under specific conditions, such as very low pH values or ionic strength. The formed multilayers are unstable at high pH or in a high ionic strength environment. Therefore, the formation of highly stable multilayers of zwitterionic polymers via the LBL assembly process is still challenging. Here, we report the LBL assembly of poly(sulfobetaine methacrylate) (PSBMA) with a polyphenol, tannic acid (TA), for protein-resistant surfaces. The assembly process was monitored by a quartz crystal microbalance (QCM) and variable-angle spectroscopic ellipsometry (VASE), which confirms the formation of thin multilayer films. We found that the (TA/PSBMA)n multilayers are stable over a wide pH range of 4-10 and in saline, such as 1 M NaCl or urea solution. The surface morphology and chemical composition were characterized by specular reflectance Fourier transform infrared spectroscopy (FTIR/SR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Furthermore, (TA/PSBMA)n multilayers show high hydrophilicity, with a water contact angle lower than 15°. A QCM was used to record the dynamic protein adsorption process. Adsorption amounts of bovine serum albumin (BSA), lysozyme (Lys), and hemoglobin (Hgb) on (TA/PSBMA)20 multilayers decreased to 0.42, 52.9, and 37.9 ng/cm(2) from 328, 357, and 509 ng/cm(2) on a bare gold chip surface, respectively. In addition, the protein-resistance property depends upon the outmost layer. This work provides new insights into the LBL assembly of zwitterionic polymers.
Flexible
strain sensors have attracted a great amount of attention
for promising applications in next-generation artificially intelligent
devices. However, it is difficult for conventional planar strain sensors
to meet the requirements of miniature size and light weight for flexible
electronics. Herein, a highly sensitive and stretchable fiber strain
sensor with a millimeter diameter was innovatively fabricated by the
capillary tube method to integrate silver nanowires (AgNWs) in polyurethane
(PU) fibers. Scanning electron microscopy results demonstrate that
AgNWs were embedded into the surface layer of PU fibers and formed
completely conductive networks. The unique AgNW networks endow the
PU/AgNW fibers with superior electrical conductivity of 3.1 S/cm,
high elongation at break of 265%, wide response range of 43%, high
gauge factor of 87.6 up to 22% strain, fast response time of 49 ms,
and excellent reliability and stability. Such satisfactory stretchability
and sensitivity is attributed to the combination of the highly stretchable
PU matrix and the embedded architecture of the AgNW conductive network.
Moreover, PU/AgNW fibers can be employed as wearable devices to detect
various human motions and to drive light-emitting diodes at a lower
voltage (2.7 V).
The
pressure sensor with high sensitivity and a broad pressure
sensing range is highly desired for flexible electronics. Here, a
high-performance pressure sensor based on a hybrid structure was facilely
fabricated using the glass template method, which consists of polyurethane
(PU) mesodomes embedded with gradient-distributed silver nanowire
(AgNW). Such a novel hybrid architecture enables the as-prepared PU/AgNW
pressure sensor to have high sensitivity as well as a wide detection
range. Moreover, the obtained PU/AgNW pressure sensors have a fast
response time (20 ms), good cycling stability, and excellent flexibility.
The pressure sensor, benefiting from its outstanding comprehensive
sensing performance, can be used for expression recognition and human
activity monitoring, showing tremendous application potential in wearable
devices. The proposed architecture and developed methodology in this
work is promising for future flexible electronic applications.
In modern times, with the rapid development of technology, science and economy, applications of electromagnetic (EM) wave absorption in both commercial and military fields have increased. Meanwhile, the problems brought by EM wave absorption have gradually become obvious, such as signal interference, back-radiation of microstrip radiators and so on. Furthermore, the impact of EM wave radiation on human health has also attracted much public attention. In this regard, the application of EM wave absorbing materials has become a focus of current research. Due to their unique chemical, physical, and mechanical properties, carbon nanotubes (CNTs), through certain modifications for light mass, wide range and strong absorption, have great potential to be used as excellent EM wave absorbents. This review highlights recent research into the modification of CNTs, with special emphasis on their EM wave absorbing ability.
Pluronic F127 diacrylate (F127DA) micelle-crosslinked methacrylated hyaluronic acid (MeHA) hydrogel with low-swelling and strong compressive properties was successfully synthesized for the regeneration of cartilages in vivo.
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