Conductive hydrogels have become one of the most promising materials for skin-like sensors because of their excellent biocompatibility and mechanical flexibility. However, the limited stretchability, ...low toughness, and fatigue resistance lead to a narrow sensing region and insufficient durability of the hydrogel-based sensors. In this work, an extremely stretchable, highly tough, and anti-fatigue conductive nanocomposite hydrogel is prepared by integrating hydrophobic carbon nanotubes (CNTs) into hydrophobically associated polyacrylamide (HAPAAm) hydrogel. In this conductive hydrogel, amphiphilic sodium dodecyl sulfate was used to ensure uniform dispersion of CNTs in the hydrogel network, and hydrophobic interactions between the hydrogel matrix and the CNT surface formed, greatly improving the mechanical properties of the hydrogel. The obtained CNTs/HAPAAm hydrogel showed excellent stretchability (ca. 3000%), toughness (3.42 MJ m–3), and great anti-fatigue property. Moreover, it exhibits both high tensile strain sensitivity in the wide strain ranges (gauge factor = 4.32, up to 1000%) and high linear sensitivity (0.127 kPa–1) in a large-pressure region within 0–50 kPa. The CNTs/HAPAAm hydrogel-based sensors can sensitively and stably detect full-range human activities (e.g., elbow rotation, finger bending, swallowing motion, and pronouncing) and handwriting, demonstrating the CNTs/HAPAAm hydrogel’s potential as the wearable strain and pressure sensors for flexible devices.
Abstract
Zwitterionic hydrogels exhibit eminent nonfouling and hemocompatibility. Several key challenges hinder their application as coating materials for blood-contacting biomedical devices, ...including weak mechanical strength and low adhesion to the substrate. Here, we report a poly(carboxybetaine) microgel reinforced poly(sulfobetaine) (pCBM/pSB) pure zwitterionic hydrogel with excellent mechanical robustness and anti-swelling properties. The pCBM/pSB hydrogel coating was bonded to the PVC substrate via the entanglement network between the pSB and PVC chain. Moreover, the pCBM/pSB hydrogel coating can maintain favorable stability even after 21 d PBS shearing, 0.5 h strong water flushing, 1000 underwater bends, and 100 sandpaper abrasions. Notably, the pCBM/pSB hydrogel coated PVC tubing can not only mitigate the foreign body response but also prevent thrombus formation ex vivo in rats and rabbits blood circulation without anticoagulants. This work provides new insights to guide the design of pure zwitterionic hydrogel coatings for biomedical devices.
Intraperitoneal adhesions are common and serious complications after surgery. Deposition of proteins and inflammatory response on an injured cecum are the main factors resulting in the formation of ...adhesion. In this study, purely zwitterionic hydrogels (Z-hydrogels) are developed using thiolated poly(sulfobetaine methacrylate-co-2-((2-hydroxyethyl)disulfanyl)ethyl methacrylate) poly(SBMA-co-HDSMA) as the network backbone and divinyl-functionalized sulfobetaine (BMSAB) as the zwitterionic cross-linker via the thiol–ene click reaction. To improve the anti-inflammatory activity, cefoxitin sodium is loaded into Z-hydrogels (Z/C-hydrogel) to construct the physical barrier/drug system. The gelation time, mechanical behavior, and swelling ratio of the prepared Z-hydrogel can be modulated via adjusting the SBMA/HDSMA ratio in the copolymer. Moreover, they not only exhibit excellent resistance to protein and fibroblast adhesion but also show good biocompatibility and hemocompatibility. To assess its anti-adhesion effects in vivo, the Z-hydrogel is injected on the injured cecum surface using a rat model of sidewall defect-cecum abrasion. The results show that the Z-hydrogel can completely cover the irregular cecum surface and effectively suppress the formation of postoperative adhesion via reducing protein deposition and resisting fibroblast adhesion. Moreover, the introduction of cefoxitin sodium decreases the inflammatory response after surgery, thus further improving the anti-adhesion effect. Overall, we suggest that the Z-hydrogel is a promising candidate for the prevention of a postsurgical peritoneal adhesion.
Hydrogel-based strain sensors have been widely investigated owing to their intrinsic flexible and extensible properties. However, integrating good mechanical properties and excellent strain ...sensitivity into one hydrogel remains a challenge. In this work, a dual physical cross-linked carboxymethyl cellulose-Fe
3+
/polyacrylamide (CMC-Fe
3+
/PAAm) double network hydrogel was developed by facile two-step method. In this hydrogel, the Fe
3+
cross-linked CMC acts as the first network for dissipating energy and hydrophobic association PAAm acts as the second network to maintain the integrity of hydrogel. Owing to these physical interactions, the as-prepared hydrogel shows good mechanical properties (e.g., tensile strength, 1.82 MPa; toughness, 6.52 MJ/m
3
). Furthermore, these mechanical behaviors can be modulated by adjusting the solid content, CMC/PAAm ratio, Fe
3+
concentration and soaking time in Fe
3+
solution. Moreover, the obtained hydrogel shows excellent self-recovery and anti-fatigue property due to the reversibility of dual physical cross-linked interactions. Additionally, the CMC-Fe
3+
/PAAm hydrogel shows good conductivity (1.82 S/m), strain sensitivity (gauge factor = 4.02 at 50–600% strain), and fast response time (260 ms). Based on the high strain sensitivity, the CMC-Fe
3+
/PAAm hydrogel can fabricate a flexible strain sensor for precisely monitoring various human motions. This study suggests that the CMC-Fe
3+
/PAAm hydrogel exhibits potential application in the flexible and stretchable strain sensors.
Graphic abstract
•Lignin and Chinese fir valorization.•An efficient catalyzing system of lignin-derived acids and borate was developed.•Lignin-based catalyst is more compatible with furfural alcohol resin.•Excellent ...dimensional stability was achieved after furfurylation.•Compressive strength of Chinese fir was increased by 45.4% after furfurylation.
In order to valorize lignin from spent liquor of pulping mills, a novel catalyzing system for wood furfurylation which composed of lignin-derived acids (LDAs, i.e. lignosulfonic acid and sulfomethylated lignin acid) and buffer sodium borate was developed, and was applied to Chinese fir furfurylation for improved dimensional stability and mechanical properties. LDAs were prepared by protonating of sulfomethylated lignin and lignosulfonate through cation exchange resin. The catalyzing system was optimized by the storage duration of FA formulas with respective catalyzing system at room temperature and the curing time at elevated temperature. Then, three formulas were selected out to treat Chinese fir and their performance was evaluated by weight percentage gain, dimensional stability, and compressive strength. The results showed that LDAs, especially sulfomethylated lignin acid, penetrated into cell walls and catalyzed furfurylation reaction quite well. The best performance achieved in this study by Formula III was with weight percentage gain of 66.4%, equilibrium moisture content 12.9%, anti-swelling efficiency 61.9% and 70.6% for the conditions of high humidity and water-soaking, respectively; its parallel-to-grain compressive strength was improved by 45.4%. It hints lignin-derived acids combined with borate would be a promising catalyst system for wood furfurylation since it valorizes both the waste lignin and low-valued wood.
Low-power, high-speed dynamic comparators are highly desirable in the design of high-speed analog-to-digital converters (ADC) and digital I/O circuits. Most dynamic comparators use a pair of ...cross-coupled inverters as the latching stage, which provides strong positive feedback, to accelerate the comparison and reduce the static power consumption. The delay of the comparator is mainly determined by the total effective transconductance of the latching stage. The delay not only limits the maximum operating frequency but also extends the period of the metastable state of the latching stage; hence, it increases energy consumption. However, at the beginning of the comparison phase, the conventional latching stage has two transistors with zero gate-to-source voltage, which degrade the total effective transconductance of the latching stage. In this paper, a novel low-power, high-speed dynamic comparator with a new latching stage is presented. The proposed latching stage uses separated gate-biasing cross-coupled transistors instead of the conventional cross-coupled inverter structure. The simple proposed latching stage improves its effective total transconductance at the beginning of the comparison phase, which leads to a much faster comparison and lowers energy consumption. The comparator is analyzed and compared to its prior type in terms of delay and power consumption via simulations and measurements. The experimental results demonstrate that the proposed comparator operates from a 1.2-V supply and consumes 110-fJ energy per comparison, with sampling speeds up to 2 GS/s.
Bacterial sulfate reduction (BSR) is one of the key factors leading to the anomalous accumulation of hydrogen sulphide in coal mines. Environmental factors such as temperature and pH play a crucial ...role in the metabolism and degradation of coal by sulfate-reducing bacteria (SRB). In this study, coal samples were selected from Shengli Coal Mine, and SRB strains were isolated and purified from mine water using a dilution spread-plate anaerobic cultivation method. Based on single-factor experiments and response surface methodology (RSM), the impact of temperature, pH, oxidation-reduction potential (ORP), chemical oxygen demand to sulfate ratio (COD/SO
) on the generation of hydrogen sulphide during brown coal BSR was analyzed. The results showed that the anaerobic degradation of coal by SRB was inhibited by either too high or too low a temperature to produce hydrogen sulfide, and the greatest production of hydrogen sulfide occurred at a temperature of about 30 °C; The greatest production of hydrogen sulfide occurred at an initial ambient pH of 7.5; COD/SO
ratio of around 2.0 is most conducive to hydrogen sulphide generation; the lower ORP value is more favorable for hydrogen sulfide generation. The optimal conditions obtained by RSM were: temperature of 30.37 °C, pH of 7.64 and COD/SO
of 1.96. Under these conditions, the hydrogen sulfide concentration was 56.79 mg/L, the pH value was 8.40, the ORP value was -274 mV, and the SO
utilization rate was 58.04%. The RSM results showed that temperature, ambient pH and COD/SO
had a significant effect on hydrogen sulfide production, and the degree of effect was: ambient pH > temperature > COD/SO
.
Abstract
With advances in tissue engineering and bioelectronics, flexible electronic hydrogels that allow conformal tissue integration, online precision diagnosis, and simultaneous tissue ...regeneration are expected to be the next-generation platform for the treatment of myocardial infarction. Here, we report a functionalized polyaniline-based chronological adhesive hydrogel patch (CAHP) that achieves spatiotemporally selective and conformal embedded integration with a moist and dynamic epicardium surface. Significantly, CAHP has high adhesion toughness, rapid self-healing ability, and enhanced electrochemical performance, facilitating sensitive sensing of cardiac mechanophysiology-mediated microdeformations and simultaneous improvement of myocardial fibrosis-induced electrophysiology. As a result, the flexible CAHP platform monitors diastolic-systolic amplitude and rhythm in the infarcted myocardium online while effectively inhibiting ventricular remodeling, promoting vascular regeneration, and improving electrophysiological function through electrocoupling therapy. Therefore, this diagnostic and therapeutic integration provides a promising monitorable treatment protocol for cardiac disease.
Zwitterions have aroused much interest to endow implantable medical devices with anti-fouling and anti-thrombosis performance, due to their ability to form a hydrated layer that can provide a good ...barrier against protein and cell adhesion. Herein, tyramine modified sulfobetaine-derived sodium hyaluronan (HST) hydrogel coating was fabricated, in which hyaluronan (HA) was used as polysaccharide skeleton to graft zwitterionic sulfobetaine, and tyramine was introduced as crosslinker to construct both the network of hydrogel and a strong covalent bond between coating and substrate. Hydrogel coating was prepared by spin coating or painting HST prepolymer solution under ultraviolet light irradiation. The obtained HST hydrogel coating shows good stability. Moreover, in addition to its outstanding anti-fouling performance and good biocompatibility, it can effectively prevent thrombosis in blood circulation
ex vivo
. This work offers a universal strategy to prepare a high-performance anti-fouling and anti-thrombosis coating, which is expected to promote the development of functional coatings for biomedical materials.
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