Kirigami‐Structured, Low‐Impedance, and Skin‐Conformal Electronics for Long‐Term Biopotential Monitoring and Human–Machine Interfaces

Abstract Epidermal dry electrodes with high skin‐compliant stretchability, low bioelectric interfacial impedance, and long‐term reliability are crucial for biopotential signal recording and human–machine interaction. However, incorporating these essential characteristics into dry electrodes remains a challenge. Here, a skin‐conformal dry electrode is developed by encapsulating kirigami‐structured poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/polyvinyl alcohol (PVA)/silver nanowires (Ag NWs) film with ultrathin polyurethane (PU) tape. This Kirigami‐structured PEDOT:PSS/PVA/Ag NWs/PU epidermal electrode exhibits a low sheet resistance (≈3.9 Ω sq−1), large skin‐compliant stretchability (>100%), low interfacial impedance (≈27.41 kΩ at 100 Hz and ≈59.76 kΩ at 10 Hz), and sufficient mechanoelectrical stability. This enhanced performance is attributed to the synergistic effects of ionic/electronic current from PEDOT:PSS/Ag NWs dual conductive network, Kirigami structure, and unique encapsulation. Compared with the existing dry electrodes or standard gel electrodes, the as‐prepared electrodes possess lower interfacial impedance and noise in various conditions (e.g., sweat, wet, and movement), indicating superior water/motion‐interference resistance. Moreover, they can acquire high‐quality biopotential signals even after water rinsing and ultrasonic cleaning. These outstanding advantages enable the Kirigami‐structured PEDOT:PSS/PVA/Ag NWs/PU electrodes to effectively monitor human motions in real‐time and record epidermal biopotential signals, such as electrocardiogram, electromyogram, and electrooculogram under various conditions, and control external electronics, thereby facilitating human–machine interactions.


Figure S2 .
Figure S2.(a) Nyquist diagram of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode-skin system, and the experimental values fit well with the simulated values of the contact impedance of electrode-skin system.(b) Measured and simulated contact impedance.These excellent fits indicate the rationality of the equivalent circuit model.

Figure S6 .
Figure S6.(a) The digital images show that the PEDOT:PSS/PVA films with low PVA loadings are broken while being detached.(b) Stress-strain curves of PEDOT:PSS/PVA films with different PVA loadings.

Figure S7 .
Figure S7.The surficial morphologies of PEDOT:PSS/PVA/Ag NWs films after experiencing peeling tests by 3M tape.The addition of water can enhance the interfacial interactions between Ag NWs and PEDOT:PSS/PVA films.

Figure S9 .
Figure S9.SEM images of Ag NWs in the PEDOT:PSS/PVA/Ag NWs film.

Figure S11 .
Figure S11.(a, b) Fluorescent images of stained NIH 3T3 cells cultured on control substrate and PEDOT:PSS/PVA/Ag NWs film after 72h.Live cells: green.Dead cells: red.(c) Cell viability rate at 24 h and 72 h of incubation.

Figure S13 .
Figure S13.(a) Digital images of brightness changes of LED light during the stretch-release process of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode.(b, c) Resistance changes of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes fabricated without prestretch process (b) and with prestretch process (c) at various strains, respectively.Insets are the digital images of the corresponding electrodes.(d) Resistance change of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode under 30% strain at diverse frequencies.

Figure S14 .
Figure S14.Simulated stress distributions of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs film and Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode at different strains.When same strains are exerted, Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes bear less stress at the fracture points due to the protection of PU tape, and it is more difficult to break, preventing damage to the conductive network.

Figure S15 .
Figure S15.Stretching processes of Kirigami patterns with different cutting sizes.

Figure S16 .
Figure S16.Top view of a Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode on skin with different deformation.

Figure S17 .
Figure S17.(a) Interfacial impedance of different electrode-skin systems from 0.1 to 10 5 Hz.(b) Comparison of interfacial impedance of different electrode-skin systems in different conditions at 10 Hz and 100 Hz.

Figure S20 .
Figure S20.(a) Weight loss percentage of commercial electrodes placed at room temperature for different time.(b) Interfacial impedance of commercial electrodes placed at room temperature for different times.(c) ECG signals recorded with commercial electrodes placed for 72 hours and 0 hours.

Figure S22 .
Figure S22.ECG signals recorded by Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes and commercial electrodes after arms are immersed in water, removed from water, and dried, and ECG signals recorded by wristband after exercise.

Figure S23 .
Figure S23.The RMS noise calculated from the baseline between T and P waves of ECG signals picked by Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes and commercial electrodes during ECG recording under different circumstances (e.g., moving, wet skin, sonication, and under water).

Figure S24 .
Figure S24.(a) Spectra of the EMG pulse recorded using the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode and commercial electrodes.(b) Variations of the EMG signal amplitude with different gripping force.(c) EMG signal amplitude produced by the flexion/extension of different fingers.(d) Time-domain EEG signals of open eyes and closed eyes recorded by the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode.(e) Spectra of the EEG signal with eyes

Figure S25 .
Figure S25.(a, b) Layout of circuit with the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes for applications in the operations of music play/switch using EOG signals (a) and snake game using EMG signals (b).

Figure S26 .
Figure S26.Measured points of sheet resistance on one sample.

Figure S27 .
Figure S27.Method of metal wires connected to epidermal electrodes.

Figure S2 .
Figure S2.(a) Nyquist diagram of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode-skin system, and the experimental values fit well with the simulated values of the contact impedance of electrode-skin system.(b) Measured and simulated contact impedance.These excellent fits indicate the rationality of the equivalent circuit model.

Figure S6 .
Figure S6.(a) The digital images show that the PEDOT:PSS/PVA films with low PVA loadings are broken while being detached.(b) Stress-strain curves of PEDOT:PSS/PVA films with different PVA loadings.

Figure S7 .
Figure S7.The surficial morphologies of PEDOT:PSS/PVA/Ag NWs films after experiencing peeling tests by 3M tape.The addition of water can enhance the interfacial interactions between Ag NWs and PEDOT:PSS/PVA films.

Figure S9 .
Figure S9.SEM images of Ag NWs in the PEDOT:PSS/PVA/Ag NWs film.

Figure S11 .
Figure S11.(a, b) Fluorescent images of stained NIH 3T3 cells cultured on control substrate and PEDOT:PSS/PVA/Ag NWs film after 72h.Live cells: green.Dead cells: red.(c) Cell viability rate at 24 h and 72 h of incubation.

Figure S13 .
Figure S13.(a) Digital images of brightness changes of LED light during the stretch-release process of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode.(b, c) Resistance changes of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes fabricated without prestretch process (b) and with prestretch process (c) at various strains, respectively.Insets are the digital images of the corresponding electrodes.(d) Resistance change of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode under 30% strain at diverse frequencies.

Figure S14 .
Figure S14.Simulated stress distributions of the Kirigami-structured PEDOT:PSS/PVA/Ag NWs film and Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode at different strains.When same strains are exerted, Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes bear less stress at the fracture points due to the protection of PU tape, and it is more difficult to break, preventing damage to the conductive network.

Figure S15 .
Figure S15.Stretching processes of Kirigami patterns with different cutting sizes.

Figure S16 .
Figure S16.Top view of a Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode on skin with different deformation.

Figure S17 .
Figure S17.(a) Interfacial impedance of different electrode-skin systems from 0.1 to 10 5 Hz.(b) Comparison of interfacial impedance of different electrode-skin systems in different conditions at 10 Hz and 100 Hz.

Figure S20 .
Figure S20.(a) Weight loss percentage of commercial electrodes placed at room temperature for different time.(b) Interfacial impedance of commercial electrodes placed at room temperature for different times.(c) ECG signals recorded with commercial electrodes placed for 72 hours and 0 hours.

Figure S22 .
Figure S22.ECG signals recorded by Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes and commercial electrodes after arms are immersed in water, removed from water, and dried, and ECG signals recorded by wristband after exercise.

Figure S23 .
Figure S23.The RMS noise calculated from the baseline between T and P waves of ECG signals picked by Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes and commercial electrodes during ECG recording under different circumstances (e.g., moving, wet skin, sonication, and under water).

Figure S24 .
Figure S24.(a) Spectra of the EMG pulse recorded using the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrode and commercial electrodes.(b) Variations of

Figure S25 .
Figure S25.(a, b) Layout of circuit with the Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes for applications in the operations of music play/switch using EOG signals (a) and snake game using EMG signals (b).

Figure S26 .
Figure S26.Measured points of sheet resistance on one sample.

Figure S27 .
Figure S27.Method of metal wires connected to epidermal electrodes.

Table S1 .
Comparison of our Kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes with the reported electrodes

Table S2 .
Sample Naming Explanation

Table S1 .
Comparison of our kirigami-structured PEDOT:PSS/PVA/Ag NWs/PU electrodes with the reported electrodes

Table S2 .
Sample Naming Explanation