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Ma et al. Soft Sci 2024;4:26 https://dx.doi.org/10.20517/ss.2024.20 Page 25 of 34

Table 5. Summary of typical LIG-based soft bio-actuators for intelligent healthcare
Device Performance Intelligent healthcare applications Ref.
configuration
Strain sensor/ GF: 316.3; sound generation: 200 Hz - 20 kHz Health monitoring and alarm of CVD and sleep apnea [44]
sound alarm
Strain sensor/ GF: 950; temperature range: 25~88.5 °C Healthcare monitoring and timely warning [45]
heater
Sound sensor/ Sound detection: 0-2 kHz; Recognized daily words vaguely spoken by a patient with [46]
artificial throat sound generation: 100-20 kHz, 60 dB laryngectomy
-1
Pressure sensor/ Sound sensing sensitivity: 45,000 mV·Pa ; Artificial intelligence communication based on recognized speech [108]
artificial mouth sound-producing frequency range: 20 Hz - 20 kHz features
LIG: Laser-induced-graphene; GF: gauge factor; CVD: cardiovascular disease.

[Figure 13A] . The fabricated lithium-ion battery presented a high reversible areal capacity of
[48]
-2
approximately 280 μA·h·cm . Furthermore, it exhibited a stable performance for at least 100 cycles with an
average coulombic efficiency of 99%. In addition, biochemical energy can be effectively converted into
electricity by enzymatic biofuel cells (EBFCs), which probably supplies continuous and stable power outputs
[120]
for integrated biosensors . Motivated by this, Huang et al. developed AuNPs/LIG composites-based
transient glucose EBFCs (TEBFCs) [Figure 13B] . The AuNPs/LIG electrode exhibited better than the pure
[71]
LIG electrode, probably due to its low electric impedance and large surface area [Figure 13C]. The
developed TEBFC showcased outstanding output performance with an open circuit potential of 0.77 V and
a maximum power density of 483.1 μW/cm . Meanwhile, benefiting from poly(lactic-coglycolic acid) (PLGA)
2
substrate, the TEBFCs can be degraded and absorptive inside animal bodies in 44 days. The TEBFC could be
a transient power source for low-power implantable bioelectronics.

TENGs can convert external mechanical energy into electricity by combining the triboelectric effect and
electrostatic induction . Our daily activities (walking, typing, joint movement, etc.) provide a ceaseless
[121]
mechanical stimulus source for energy collection. Motivated by this, LIG is widely used as electrodes to
fabricate high-performance soft skin electronics, collect energy, and record physiological signals. Stanford
et al. reported a stretchable and flexible single-electrode TENG based on LIG/PDMS composites, generating
power by contacting skin [Figure 13D]. The developed LIG/PDMS-based TENG was inserted into a shoe,
[122]
effectively demonstrating mechanical energy harvesting. The results revealed that the developed TENG
showcased a peak power output of 1.2 mW (0.33 Wm ) as a load resistance of 70 MΩ.
-2

Meanwhile, Das et al. created a LIG-based self-powered triboelectric pressure sensor, which consisted of
three layers, i.e., a LIG/PI film acting as the bottom electrode, a microstructured PDMS layer, and a PET/
indium tin oxide (ITO) film with opposite triboelectric polarity [Figure 13E]. The fabricated pressure
[49]
-1
sensor exhibited a fast response time (9.9 ms) and a high sensitivity (7.697 kPa ), which is beneficial for
telemedicine. For instance, a clear pulse waveform could be recorded from a human finger on the pressure
sensor. In addition, Yang et al. reported a stretchable TENG by integrating AgNWs/LIG electrodes with
triboelectric MXene/PDMS-Ecoflex composites for mechanical energy collection and mechanical signal
perception . The stretchable AgNWs/LIG electrodes were developed by spray coating the AgNWs on pre-
[70]
stretched LIG/PDMS-Ecoflex substrates. These electrode designs endowed the developed TENG with stable
performance even under 30% tensile strain, outperforming most of the previously related works. Besides,
the stretchable TENG can be conformally attached to 3D complicated surfaces, for instance, integrated onto
human skin for human movement monitoring [Figure 13F].