Smart epidermal electrophysiological electrodes:Materials,structures,and algorithms

Epidermal electrophysiological monitoring has garnered significant attention for its potential in medical diagnosis and healthcare,particularly in continuous signal recording.However,simultaneously satisfying skin compliance,mechanical properties,environmental adaptation,and biocompatibility to avoid signal attenuation and motion artifacts is challenging,and accurate physiological feature extraction necessitates effective signal-processing algorithms.This review presents the latest advancements in smart electrodes for epidermal electrophysiological monitoring,focusing on materials,structures,and algorithms.First,smart materials incorporating self-adhesion,self-healing,and self-sensing functions offer promising solutions for long-term monitoring.Second,smart meso-structures,together with micro/nanostructures endowed the electrodes with self-adaption and multifunctionality.Third,intelligent algorithms give smart electrodes a“soul,”facilitating faster and more-accurate identification of required information via automatic processing of collected electrical signals.Finally,the existing challenges and future opportunities for developing smart electrodes are discussed.Recognized as a crucial direction for next-generation epidermal electrodes,intelligence holds the potential for extensive,effective,and transformative applications in the future.

Stretchable,breathable,and washable epidermal electrodes based on microfoam reinforced ultrathin conductive nanocomposites

Stretchable epidermal electronics allow conformal interactions with the human body for emerging applications in wearable health monitoring and therapy.Stretchable devices are commonly constructed on submillimeter-thick elastomer substrates with limited moisture permeability,thereby leading to unpleasant sensations during long-term attachment.Although the ultrathin elastomer membrane may address this problem,the mechanical robustness is essentially lost for direct manipulations and repetitive uses.Here,we report a stretchable,breathable,and washable epidermal electrode of microfoam reinforced ultrathin conductive nanocomposite(MRUCN).The new architecture involves ultrathin conductive silver nanowire nanocomposite features supported on a porous elastomeric microfoam substrate,which exhibits high moisture permeability for pleasant perceptions during epidermal applications.As-prepared epidermal electrodes show excellent electronic conductivity(8440 S·cm^(-1)),high feature resolution(~50μm),decent stretchability,and excellent durability.In addition,the MRUCN retains stable electrical properties during washing to meet the hygiene requirements for repetitive uses.The successful implementation in an integrated electronic patch demonstrates the practical suitability of MRUCN for a broad range of epidermal electronic devices and systems.

An injectable,self-healable,and reusable PEDOT:PSS/PVA hydrogel patch electrode for epidermal electronics

Injectability empowers conductive hydrogels to transcend traditional limitations,unlocking a realm of possibilities for innovative medical,wearable,and therapeutic applications that can significantly enhance patient care and quality of life.Here,we report an injectable,self-healable,and reusable hydrogel obtained by mixing the concentrated poly(3,4-ethylenedioxythiophene)doped with polystyrene sulfonate(PEDOT:PSS)suspension(~2 wt.%solid content),polyvinyl alcohol(PVA),and borax.Leveraging the presence of reversible borax/hydroxyl bonds and multiple hydrogen bonds,this PEDOT:PSS/PVA hydrogel exhibits notable shear-thinning behavior and self-healing capabilities,enabling it to be injected as a gel fiber from a syringe.As-prepared injectable hydrogel also demonstrates an ultra-low modulus(~2.5 MPa),reduced on-skin impedance(~45%of commercial electrodes),and high signal-to-noise ratio(SNR)(~15-22 dB)in recording of electrocardiography(ECG),electromyography(EMG),and electroencephalogram(EEG)signals.Furthermore,the injectable hydrogels can be remolded and reinjected as the reusable electrodes,maintaining nearly identical electrophysiological recording capabilities and brain-computer interface(BCI)performance compared to commercial wet electrodes.With their straightforward fabrication,excellent material properties and electronic performance,ease of cleaning,and remarkable reusability,our injectable PEDOT:PSS/PVA hydrogels hold promise for advancements in BCI based electronics and wearable bioelectronics.