β‐Phase‐Rich Laser‐Induced Hierarchically Interactive MXene Reinforced Carbon Nanofibers for Multifunctional Breathable Bioelectronics

Abstract

Hierarchically interactive 3D‐porous soft carbon nanofibers (CNFs) have great potential for wearable bioelectronic interfaces, yet 90% of CNFs are derived from expensive polyacrylonitrile associated with complex production methods. Here, another cost‐effective fluoropolymer, poly(1,1‐difluoroethylene) (PDFE), is introduced to investigate its transition chemistry and structural evolution over laser‐induced carbonization (LIC). The impregnation of Ti3C2Tx‐MXene followed by dehydrofluorination is believed to be crucial to enhance the β‐phase and reinforce PDFE‐based nanofibers. It is explored that the β‐phase of the dehydrofluorinated MXene‐PDFE nanofibers is converted into an sp2‐hybridized hexagonal graphitic structure by cyclization/cross‐linking decomposition during LIC. Remarkably, this approach generates laser‐induced hierarchical CNFs (LIHCNFs) with a high carbon yield (54.77%), conductivity (sheet resistance = 4 Ω sq−1), and stability over 500 bending/releasing cycles (at 10% bending range). Using LIHCNFs, a skin‐compatible breathable and reusable electronic‐tattoo is engineered for monitoring long‐term biopotentials and human–machine interfaces for operating home electronics. The LIHCNFs‐tattoo with high breathability (≈14 mg cm−2 h−1) forms compliant contact with human skin, resulting in low electrode‐skin impedance (23.59 kΩ cm2) and low‐noise biopotential signals (signal‐to‐noise ratio, SNR = 41 dB). This finding offers a complementary polymer precursor and carbonization method to produce CNFs with proper structural features and designs for multifunctional biointerfaces.

Toward a new generation of permeable skin electronics

“…The bioelectrical tattoo had a great permeability (14 mg cm −2 h −1 ) due to its porous substrate, and can be utilized for ECG, EMG and EEG monitoring. 177 ECG signals can be derived by directly measuring the distance from the LIHCNF tattoos to the vibrator (Fig. 9b).…”

“…9d). 177 The other method is to fabricate bioelectrical sensors based on porous substrates. Various conductive materials, such as metals, carbon-based materials, and conductive polymers, can be grown in situ on porous substrates.…”

Two-Dimensional Nanomaterials beyond Graphene for Biomedical Applications

“…The LIHCNFs tattoos revealed low resistance of 4 Ω sq −1 with impedance as low as 23.59 kΩ cm 2 at 10 Hz compared to dry electrodes such as graphitized electrospun fiber [ 87 ], Au thin film/polyimide [ 88 ] or laser-induced porous graphene [ 89 ]. The LIHCNFs tattoos also have high signal to noise ratio of 41 dB and are suitable for long-term monitoring, revealing high durability even after 24h use [ 90 ]. The proposed bioelectronic tattoo is a potential candidate for the development of wearable human-machine biointerfaces.…”

Conductive Cellulose-Derived Carbon Nanofibrous Membranes with Superior Softness for High-Resolution Pressure Sensing and Electrophysiology Monitoring

“…Softness (compliance) is another significant performance index for CNF films to be used in a wide variety of applications ranging from human–machine biointerfaces to personal health care and to human physiology. , It is of great advantage that soft film electronics form a compliant and tight contact with skin or collector to enhance the quality of detecting signals. A few studies have been developed to soften synthetic polymer-derived CNFs (SP-CNFs), such as pore creation on nanofibrils via etching with corrosive agents or evaporating sacrificial polymers in nanofibers, − and adjustment of the net microstructure ( i.e.…”