Compressible Supercapacitor with Residual Stress Effect for Sensitive Elastic-Electrochemical Stress Sensor

Thermodynamic behavior and crystal structure of polypropylene treated with supercritical carbon dioxide

Controlling temperature and pressure during the supercritical carbon dioxide (scCO2) process can change the mount of CO2 entered in polypropylene (PP) phase, thereby changing the mechanical properties of materials. The effect of scCO2 treatment on the crystallization behavior is different in the semi-molten and molten states. This study investigates the PP treated with scCO2 near the melting point and at various pressures, and explores the effects of temperature and pressure on the crystal structure, lamellar structure, and thermodynamic properties of PP. The results show that at a melting temperature of 165 °C, scCO2 can enhances the ability of PP molecules to makes the PP crystal region more regular, and forms larger microcrystals and lamellae. Additionally, increasing the pressure can make more CO2 enter the PP crystal region and further improve the regularity of the crystal. At a semi-melting temperature of 155 °C, scCO2 is primarily in the amorphous region because it is difficult to enter the PP crystal region. Even if increasing the pressure, it has little effect on the crystal size and lamellar thickness of PP. The research has significant implications for developing and utilizing scCO2 to remove ash from materials.

Supercapacitive brophene-graphene aerogel as elastic-electrochemical dielectric layer for sensitive pressure sensors

A sensitive pressure sensor based on ultralight and superelastic supercapacitive borophene-graphene aerogel as dielectric layer is reported. The borophene-graphene aerogel not only combines large specific surface area of reduced graphene oxide and high conductivity of borophene, but also exhibits rich porous structure. The strong synergy and intercalation between two different two-dimensional materials benefit electron transfer and electrolyte ion diffusion. On the one hand, the aerogel exhibits greater mass specific capacitance of 330 F g^-1 than pure graphene aerogel. More importantly, serving as dielectric layer for pressure sensors with a symmetrical structure, the sensor represents ultra-high sensitivity (0.90 KPa^-1) in the pressure range (<3 KPa), ultra-rapid response time (~110 ms), ultra-low detection limit as 8.7 Pa and excellent working stability after 1000 cycles. In practical application, the sensor demonstrates great performance in monitoring human physiological signals, and agricultural applications.

Wearable Strain Sensors Based on a Porous Polydimethylsiloxane Hybrid with Carbon Nanotubes and Graphene

High-performance flexible strain sensors are urgently needed with the rapid development of wearable intelligent electronics. Here, a bifiller of carbon nanotubes (CNTs) and graphene (GR) for filling flexible porous polydimethylsiloxane (CNT-GR/PDMS) nanocomposites is designed and prepared for strain-sensing applications. The typical microporous structure was successfully constructed using the Soxhlet extraction technique, and the connected CNTs and GR constructed a perfect three-dimensional conductive network in the porous skeleton. As a result, the stretchability and sensitivity of the CNT-GR/PDMS-based strain sensors were well regulated based on the porous structure and the typical synergistic conductive network. Based on the destruction effect of the brittle synergistic conductive network located in the outer and inner layers of the cell skeleton and the contact effect between adjacent cells in different strain ranges, the prepared CNTs-GR/PDMS-based strain sensor exhibited superior gauge factors of 182.5, 45.6, 70.2, and 186.5 in the 0-3, 3-57, 57-90, and 90-120% strain regions, respectively. In addition, this material also exhibited an ultralow detection limit (0.5% strain), a fast response time (60 ms), good stability and durability (10,000 cycles), and frequency-/strain-dependent sensing performances, making it active for the detection of various external environments. Finally, the prepared porous CNTs-GR/PDMS-based strain sensor was attached to the skin to detect various human motions, such as wrist bending, finger bending, elbow bending, and knee bending, thereby demonstrating wide application prospects in smart wearable devices.

Engineering of Aerogel-Based Biomaterials for Biomedical Applications

Biomaterials with porous structure and high surface area attract growing interest in biomedical research and applications. Aerogel-based biomaterials, as highly porous materials that are made from different sources of macromolecules, inorganic materials, and composites, mimic the structures of the biological extracellular matrix (ECM), which is a three-dimensional network of natural macromolecules (e.g., collagen and glycoproteins), and provide structural support and exert biochemical effects to surrounding cells in tissues. In recent years, the higher requirements on biomaterials significantly promote the design and development of aerogel-based biomaterials with high biocompatibility and biological activity. These biomaterials with multilevel hierarchical structures display excellent biological functions by promoting cell adhesion, proliferation, and differentiation, which are critical for biomedical applications. This review highlights and discusses the recent progress in the preparation of aerogel-based biomaterials and their biomedical applications, including wound healing, bone regeneration, and drug delivery. Moreover, the current review provides different strategies for modulating the biological performance of aerogel-based biomaterials and further sheds light on the current status of these materials in biomedical research.