Electrospun Polyethylene Glycol/Polyvinyl Alcohol Composite Nanofibrous Membranes as Shape-Stabilized Solid-Solid Phase Change Materials

In this work,shape-stabilized solid-solid phase change materials(PCMs)were fabricated by simply electrospinning polyethylene glycol(PEG)and polyvinyl alcohol(PVA).Owing to the strong hydrogen bonds and entanglement between those molecular chains of PEG and PVA,PEG was packaged by PVA.The morphological structures,thermal stability and thermal energy storage properties of those fibers were investigated.SEM results showed that those electrospun PVA/PEG composite membranes hold a three-dimensional nonwoven web structure even the content of PEG as high as 70%.The thermal energy storage ability of those composite fibers increased with the increase of the content of PEG.The heat enthalpies of PEG/PVA=7/3 were as high as 78.806 J/g.Moreover,those composite fibers had excellent thermal stability.After 100 heating and cooling cycles,there was almost no obvious change in the melting enthalpy and crystallization enthalpy.Those fibers still maintained good thermal regulation.The simple preparation process,low cost of raw materials and excellent stability endow the PCMs great utilization potentiality in smart textile and energy storage systems.

Versatile sensing devices for self-driven designated therapy based on robust breathable composite films

Flexible wearable electronics were developed for applications such as electronic skins,human-machine interactions,healthcare monitoring,and anti-infection therapy.But conventional materials showed impermeability,single sensing ability,and no designated therapy,which hindered their applications.Thus it was still a great challenge to develop electronic devices with multifunctional sensing properties and self-driven anti-infection therapy.Herein,flexible and breathable on-skin electronic devices for multifunctional fabric based sensing and self-driven designated anti-infection therapy were prepared successfully with cellulose nanocrystals/iron(Ⅲ)ion/polyvinyl alcohol(CNC/Fe^(3+)/PVA)composite.The resultant composite films possessed robust mechanical performances,outstanding conductivity,and distinguished breathability(3.03 kg/(m^(2)·d)),which benefited from the multiple interactions of weak hydrogen bonds and Fe^(3+) chelation and synergistic effects among CNC,polyaniline(PANI),and PVA.Surprisingly,the film could be assembled as a multifunctional sensor to actively monitor real-time physical and infection related signals such as temperature,moisture,pH,NH3,and human movements even at sweat states.More importantly,this multifunctional device could act as a self-driven therapist to eliminate bacterial by the release of Fe^(3+),which was driven by the damage of metal coordination Fe-O bonds due to the high temperature caused by infection at wound sites.Thus,the composite films had potential versatile applications in electronic skins,smart wound dressings,human-machine interactions,and self-driven anti-infection therapy.

L.S.gratefully acknowledges the financial support from the Engineering and Physical Sciences Research Council(Nos.EP/L022559/1,EP/L022559/2,EP/V050311/1,and EP/W004399/1);Royal Society(Nos.RG130230 and IE161214);H2020 Marie Skłodowska-Curie Actions(No.790666);J.S.Z.was supported by a PhD Studentship provided by Queen Mary University of London and China Scholarship Council(CSC).

Advanced energy and sensor devices with novel applications(e.g.,mobile equipment,electric vehicles,and medical-healthcare systems)are one of the important foundations of modern intelligent life.However,there are still some scientific issues that seriously hinder the further development of devices,including unsustainability,high material cost,complex fabrication process,safety issues,and unsatisfactory performance.Nanocellulose has aroused tremendous attention in recent decades,because of its abundant resources,renewability,degradability,low-cost,and unique physical/chemical properties.These merits make nanocellulose as matrix materials to fabricate advanced functional composites for use in energy-related fields extremely competitive.Here,we comprehensively discuss the recent progress of nanocellulose for emerging energy storage/harvesting and sensor applications.The preparation methodologies of nanocellulose combined with conductive materials are firstly highlighted,including carbon materials,conductive polymers,metal/metal oxide nanoparticles,metal-organic frameworks(MOFs),and covalent organic frameworks(COFs).We then focus on the nanocellulose-based advanced materials for the application in the areas of supercapacitors,lithium-ion batteries,solar cells,triboelectric nanogenerators,moisture-enabled electric generators,and sensors.Lastly,the future research directions of nanocellulose-based functional materials in energy-related devices are presented.