Memcapacitors are emerging as an attractive candidate for high‐density information storage due to their multilevel and adjustable capacitances and long‐term retention without a power supply. However, ...knowledge of their memcapacitive mechanism remains unclear and accounts for the limited implementation of memcapacitors for multilevel memory technologies. Here, repeatable and reproducible quaternary memories fabricated from hybrid perovskite (CH3NH3SnBr3) memcapacitors are reported. The device can be modulated to at least four capacitive states ranging from 0 to 169 pF with retention for 104 s. Impressively, an effective device yield approaching 100% for quaternary memory switching is achieved by a batch of devices; each state has a sufficiently narrow distribution that can be distinguished from the others and is superior to most multilevel memories that have a low device yield as well as an overlapping distribution of states. The memcapacitive switching stems from the modulated p–i–n junction capacitance triggered by Br− migration, as demonstrated by in situ element mapping, X‐ray photoelectron spectra, and frequency‐dependent capacitance measurements; this mechanism is different from the widely reported memristive switching involving filamentary conduction. The results provide a new way to produce high‐density information storage through memcapacitors.
An independent memcapacitor for quaternary memory is achieved. Four capacitive states, “OFF”, “ON1”, “ON2”, and “ON3”, are able to be repeatedly and reproducibly written/read/erased in an ITO/CH3NH3SnBr3/Au sandwich‐like device. The memcapacitive switching stems from Br– migration to modulate the p–i–n junction capacitance, which is different and independent from resistance switching in memristors.
•The compounded MCC/PDA aerogels were prepared.•Morphology and microstructure of the aerogel was tailored by changing PDA content.•The aerogel showed high adsorption ability and excellent adsorption ...selectivity.
As one of the materials from natural resources, the functionalization and application of cellulose attract increasing concerns. In this work, we reported a facile method to prepare the bio-inspired functionalization of microcrystalline cellulose (MCC) aerogel through polydopamine (PDA) coating, which was realized via the self-polymerization of dopamine in the MCC/LiBr solution followed by the freeze-drying technology. The morphological characterization showed that the pore morphologies of the compounded aerogel were influenced by the content of PDA. Adsorption measurements toward methylene blue (MB) showed that the compounded aerogel had high adsorption ability. Moreover, the compounded MCC/PDA aerogel exhibited excellent adsorption selectivity and it exhibited high efficiency to remove MB from different solutions, such as the mixed solution with anionic dyestuffs, the mixed solution with cationic dyestuffs and the mixed solution with common salt (NaCl). The high adsorption ability and excellent adsorption selectivity endows the compounded MCC/PDA aerogel with great potential applications in wastewater treatment.
Multifunctional phase change materials (PCMs) are highly desirable for the thermal management of miniaturized and integrated electronic devices. However, the development of flexible PCMs possessing ...heat energy storage, shape memory, and adjustable electromagnetic interference (EMI) shielding properties under complex conditions remains a challenge. Herein, the multifunctional PCM composites were prepared by encapsulating poly(ethylene glycol) (PEG) into porous MXene/silver nanowire (AgNW) hybrid sponges by vacuum impregnation. Melamine foams (MFs) were chosen as a template to coat with MXene/AgNW (MA) to construct a continuous electrical/thermal conductive network. The MF@MA/PEG composites showed a high latent heat (141.3 J/g), high dimension retention ratio (96.8%), good electrical conductivity (75.3 S/m), and largely enhanced thermal conductivity (2.6 times of MF/PEG). Moreover, by triggering the phase change of the PEG, the sponges displayed a significant photoinduced shape memory function with a high shape fixation ratio (∼100%) and recovery ratio (∼100%). Interestingly, the EMI shielding effectiveness (SE) can be adjusted from 12.4 to 30.5 dB by a facile compression–recovery process based on shape memory properties. Furthermore, a finite element simulation was conducted to emphasize the advantage of the MF@MA/PEG composites in the thermal management of chips. Such flexible PCM composites with high latent heat storage, light-actuated shape memory, and adjustable EMI shielding functions exhibit great potential as smart thermal management materials in military and aerospace applications.
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•Copper-coated melamine foam was prepared by an electroless plating method.•The PCMs possessed good stiffness-toughness balance and high electro-to-thermal conversion efficiency ...(85.6%).•The PCMs exhibited excellent thermal-induced shape memory property.•The thermal management of electronic devices in hot and cold environments was explored.
Flexible phase change composites (PCMs) show great potential for the thermal management in confined spaces. However, some defects such as low mechanical strength, low thermal/electrical conductivity have limited their advanced applications. In this work, flexible PCMs based on copper-coated melamine foam (MF@Cu) and polyethylene glycol (PEG) were prepared. The MF@Cu foams obtained by electroless copper plating on porous MF were used to encapsulate PEG. Due to the continuous copper network, MF@Cu foams not only enhanced the mechanical loading and encapsulation capacities of PCMs, but also imparted PCMs with electro-to-thermal conversion capability. Moreover, the MF@Cu/PEG PCMs exhibited excellent thermal-induced shape memory property by combining the elasticity of foams and the phase change of PEG. This multifunctional MF@Cu/PEG PCMs were further applied for the thermal management of electronic devices. Therefore, this study provides a strategy to prepare flexible PCMs with excellent integrated performances, which is beneficial to broaden the applications of PCMs.
Phase change materials (PCMs) are widely used in the thermal energy storage fields. However, the strong rigidity and poor photoabsorption ability of PCMs have inhibited their advanced applications. ...In this work, the flexible and light-responsive PCM composites consisting of paraffin and olefin block copolymer (OBC) filled with carbon nanotubes (CNTs) were prepared. The paraffin/OBC blend with appropriate ratio (60/40 wt%) not only has good encapsulation ability and high latent heat (111.7 J/g), but also shows thermal-actuated shape memory effect by triggering the phase transition of paraffin. Furthermore, by adding a small amount of CNTs, the paraffin/OBC/CNT composites exhibit simultaneous light-to-thermal energy storage and light-actuated shape memory capability. A light-responsive and temperature-controlled actuator is further exploited, which is beneficial for the installation and thermal management of devices with limited space. Considering the easy processing and inexpensive sources, the flexible and light-responsive PCM composites have great prospect in advanced light energy storage systems.
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•PI-coated BaTiO3 nanoparticles with ‘core-shell’-like structure were prepared.•PI@BT nanoparticles exhibited good dispersion in the PVDF composites.•The composites showed high ...dielectric constant and low dielectric loss.•PI interlayer exhibited dual effects in the composites.
Polymeric dielectric materials recently attract much attention due to their good comprehensive performances. However, it is still challenging to prepare polymeric dielectric materials with high dielectric constant, low dielectric loss and high breakdown strength. In this work, insulated polyimide (PI) interlayer with nanoscale thickness was coated on the surface of barium titanate (BaTiO3, BT) through the in-situ polymerization and subsequent thermal imidization treatment. The hybrid nanoparticles exhibited the typical ‘core-shell’-like structure with strong interfacial interaction between BT and PI. Different from the serious aggregation of BT nanoparticles, the PI@BT nanoparticles exhibited good dispersion in the poly(vinylidene fluoride) (PVDF) composite. There was strong interfacial interaction between PI and PVDF, which resulted in the decrease of crystallinity of the PVDF matrix at relatively high filler content. The flexible PVDF/PI@BT composites exhibited largely enhanced dielectric constant, suppressed dielectric loss and enhanced breakdown strength compared with the common PVDF/BT composites. It was suggested that the intense interfacial polarization at the interface between PI and BT contributed to the largely enhanced dielectric constant while the reduced interfacial polarization at the interface between PI and PVDF contributed to the suppressed dielectric loss. This work demonstrates that the nanoengineering of the interface between BT and PVDF using PI is an alternative way to fabricate the dielectric materials with excellent comprehensive performances.
To evaluate the ability of carbohydrate antigen 125 (CA125), human epididymis protein 4 (HE4), risk of ovarian malignancy algorithm (ROMA), and Copenhagen Index (CPH-I) to identify primary ovarian ...cancer (OC) from borderline and benign ovarian tumors (OTs) and explore ideal cutoff points.
A total of 684 OTs containing 276 OC patients, 116 ovarian borderline OTs and 292 benign OTs patients who underwent surgery in our hospital were included. We retrospectively searched the results of CA125 and HE4 before patients' surgery from the hospital's electronic medical records system. ROMA and CPH-I were calculated according to their menopausal status and age, respectively. Diagnostic performance of these four were assessed by drawing receiver operating characteristic (ROC) curves.
CA125, HE4, ROMA, and CPH-I were all significantly higher in OC women compared with borderline OTs (p < 0.001), followed by benign OTs (p < 0.001). Area under the curves (AUCs) for distinguishing OC were 0.850 (0.818-0.882), 0.891 (0.865-0.916), 0.910 (0.888-0.933) and 0.906 (0.882-0.930), respectively, and the corresponding ideal cutoff values for CA125, HE4, ROMA, and CPH-I were 132.5, 68.6, 23.8, and 6.4, respectively. The difference between ROMA and CPH-I was not significant (p = 0.97), but both were higher than CA125 and HE4 (p < 0.05). HE4 showed a significantly higher AUC than CA125 (p < 0.05). For postmenopausal women, CA125 performed equivalently to ROMA (p = 0.73) and CPH-I (p = 0.91).
In identifying patients with OC, ROMA and CPH-I outperformed single tumor marker. The diagnostic performance of HE4 was significantly higher than that of CA125. CA125 was more suitable for postmenopausal women.
Under servitization (one paradigm of non-ownership-transfer) business model such as sharing, a manufacturer is responsible not only for product design but also for maintenance. This paper deals with ...joint decision of product quality and maintenance under servitization. A model minimising total cost is formulated to obtain the optimal product quality, maintenance effort and maintenance times. We find that the total cost first decreases then increases with product quality, maintenance effort and maintenance times. Moderate quality and maintenance effort level are the best for the manufacturer, because too high or too low quality and effort cause too high total cost. However, preventive maintenance should be implemented as many times as possible until the failure cost is reduced to zero as long as each maintenance can save cost. Moreover, in the optimal joint decision, the product quality, maintenance effort and maintenance times are negatively correlated in pairs. In addition, we explore the impact of unit failure cost, product lifecycle, production cost, maintenance cost, and failure intensity on the manufacturer's optimal decisions. In extensions, we further take penalty cost, exponential failure distribution, discount rate, and customer usage into account. This paper provides insight for the manufacturer to jointly consider product design and maintenance under servitization.
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•Flexible phase change composites with simultaneous light-actuated shape variation property are prepared.•Elastic MF prevents the liquid leakage and imparts the composites with shape ...recovery property.•RGO network acts as a light absorption and heat transfer medium.•A deployable board used for maintaining the temperature constancy of houses is explored.
The advanced utilization of phase change materials (PCMs) is limited by the strong rigidity, liquid leakage and lack of photoabsorption ability. In this work, a novel form-stable PCM with solar-to-thermal energy storage ability and thermal/light-actuated shape memory property was prepared. Herein, paraffin wax (PW) served as a latent heat storage material and a switching phase for shape fixation, melamine foam (MF) acted as a supporting material to prevent the leakage and a permanent phase for shape recovery, and reduced graphene oxide (RGO) assembled on MF skeletons worked as a light absorption medium. Due to the light weight and abundant porosity of MF/RGO foam, the MF/RGO/PW PCMs possessed excellent encapsulation ability, high latent heat (144.8 J/g), good solar-to-thermal energy conversion and storage ability. Simultaneously, combining the elasticity of MF/RGO foam, the MF/RGO/PW PCMs exhibited thermal/light-sensitive shape memory property by triggering the phase transition of PW. The MF/RGO/PW PCMs showed excellent cyclic shape memory performance and thermal reliability. A light-sensitive and temperature-controlled board was further exploited, which could be installed on the roof of the house and maintained the temperature constancy. This study provides a strategy to prepare flexible, light-sensitive and form-stable PCMs via using the elastic MF/RGO foam as a supporting scaffold, and these PCMs have great potential in solar energy utilization and energy-saving buildings.
Recently, organic–inorganic hybrid perovskites (OIHP) are studied in memory devices, but ternary resistive memory with three states based on OIHP is not achieved yet. In this work, ternary resistive ...memory based on hybrid perovskite is achieved with a high device yield (75%), much higher than most organic ternary resistive memories. The pseudohalide‐induced 2D (CH3NH3)2PbI2(SCN)2 perovskite thin film is prepared by using a one‐step solution method and fabricated into Al/perovskite film/indium–tin oxide (glass substrate as well as flexible polyethylene terephthalate substrate) random resistive access memory (RRAM) devices. The three states have a conductivity ratio of 1:103:107, long retention over 10 000 s, and good endurance properties. The electrode area variation, impedance test, and current–voltage plotting show that the two resistance switches are attributable to the charge trap filling due to the effect of unscreened defect in 2D nanosheets and the formation of conductive filaments, respectively. This work paves way for stable perovskite multilevel RRAMs in ambient atmosphere.
Pseudohalide‐induced 2D (CH3NH3)2PbI2(SCN)3 perovskite film is prepared. The as‐fabricated memory devices perform ternary write‐once‐read‐many‐times memory behavior with high ternary device yield (74%). Even after 500 times bending, the ternary memory behavior is still maintained, indicating potential applications of 2D perovskite materials in high‐density data storage via random resistive access memory technology.
