Skip to main content
. 2023 Oct 9;15(19):4029. doi: 10.3390/polym15194029

Table 3.

Overview of electrospun electroactive and LCE-based actuators.

Composition
and Design		 Morphology Fabrication of Nonwovens Electrical and Mechanical Properties Biocompatibility Applications Ref.
CA matrix with PANI nanoparticles (0.1 wt% or 0.5 wt%) dispersed Membranes’
thickness: 100 µm		 Electrospinning:
Needle inner diameter: 0.21 mm;
Applied voltage: 20 kV;
Distance to collector: 20 cm;
Solution flow rate: 2.0 mL/h;
Solution concentration: 20 wt/v%
in DMAc/acetone 2:1 v/v 		Ionic conductivity: 8.7·10−4 S·cm−1 in pure CA, 10.6·10−4 S·cm−1, and 19.2·10−4 S·cm−1 in 0.1 wt% and 0.5 wt% CA/PANI samples, respectively Fibroblast cell line (NIH/3T3) attachments and spreading over the electrospun membranes were observed A dry PANI/CA bio-composite actuator showing electrically driven bending deformations [27]
CA matrix with
fullerenol (0.1 wt%
or 0.5 wt%) dispersed		 Nanofibers’
diameter range: 400–800 nm;
Membranes’ thickness: 100 µm		 Electrospinning:
Solution (20 wt/v%) of cellulose
acetate in DMAc/acetone (2:1 v/v) with 0.1 or 0.5 wt% fullerenols;
Needle inner diameter: 0.21 mm;
Applied voltage: 25 kV;
Distance to collector: 15 cm;
Solution flow rate: 2.0 mL/h		 Ionic conductivity:
8.2·10−4 S·cm−1 in CA,
11.5·10−4 S·cm−1, and 18.1·10−4 S·cm−1 in 0.1 wt% and 0.5 wt% CA/fullerenol samples;
Tensile strength of CA fibers: 1.6 MPa;
Tensile strength of CA fibers with 0.5 wt% fullerenol: 2.75 MPa		 All electrospun nanofibers did not show any inhibition of Escherichia coli K-12 bacteria on agar plates, indicating a good biocompatibility of the membranes Biocompatible
actuators		 [97]
PVA/PANI nanofibers deposited on interdigitated electrodes Fiber diameter between 100 and 200 nm;
density of nanofibers:
106 nanofibers per square centimeter		 Electrospinning:
Applied voltage: 20 kV;
Distance to collector: 13 cm;
Solution flow rate: 0.5 mL/h;
Solution concentration: 4% or 5% (v/v) in water;
Speed of collector: 400 rpm		 Electrical conductivity:
4% solution: 10−5 S·m−1;
5% solution: 3·10−6 S·m−1 		No data Gas sensor for ammonia detection [90]
Composite meshes of PANI and well-blended PLCL/SF with NGF
incorporated 		Fiber diameter between 683 ± 138 and 411 ± 98 nm;
average thicknesses of meshes were between 0.032 and 0.037 mm		 Electrospinning of PLCL/SF/PANI nanofibers:
Needle inner diameter: 0.51 mm;
Applied voltage: 12 kV;
Distance to collector: 5–6 cm;
Solution flow rate: 1.0 mL/h;
Solution concentration: 4% (v/v) in water;
Speed of collector: 4000 rpm
NGF-loaded PLCL/SF/PANI core–shell fibers were fabricated by coaxial electrospinning		 Electrical conductivity: 30.5 ± 3.1 mS cm−1;
Tensile strength from 5.7 ± 0.9 MPa to 13.7 ± 1.5 MPa depends on composition		 Effective support of rat pheochromocytoma 12 (PC12) neurite outgrowth, increased percentage of neurite-bearing cells and the median neurite length;
enhanced proliferation and decrease in the toxicity effect of PANI in Schwann cells		 Electrical stimulation and nerve growth factor (NGF) on neuron growth [91]
Blends of PANI and PLCL Fiber diameter between 100 and 800 nm Electrospinning of PANI/PLCL:
Solution concentration (v/v %): 15:85 in HFP (0.515 g/mL);
Needle inner diameter: 0.337 mm;
Applied voltage: 18–20 kV;
Distance to collector: 20 cm;
Solution flow rate: 20 µL/min;
Speed of collector: 2600 rpm 		Electrical conductivity:
about 0.00641 S·cm−1 		Based on viability tests, morphological changes, and expression of differentiation proteins in PC12 cells, PANI/PLCL fibers enhanced the NGF-induced neurite outgrowth of PC12 cells Development of electrically conductive, engineered nerve grafts [92]
PEDOT nanofibers obtained on the
electrospun PVP		 Fiber diameter of 350 ± 60 nm (1) Electrospinning of PVP:
Needle inner diameter: 0.58 mm;
Applied voltage: 27 ± 1 kV;
Distance to collector: 15 cm;
Solution flow rate: 1.0 mL/h;
Solution concentration: 1.0 and 1.5 wt% in iron(III) p-TS 40 wt% in butanol
(2) In situ vapor-phase polymerization of EDOT
(3) Removal of PVP		 Electrical conductivity:
60 ± 10 S·cm−1 		No data Electronic devices requiring flexibility and/or significant surface area, such as sensors or energy storage systems [94]
The PVA/PANI hybrid mat consisted of PANI nanostructures grown on the surface of individual nanofibers;
in the wet state, mats were rolled up
conveniently into
a multilayered
cylindrical structure 		Diameter of PVA nanofibers: 450 nm;
individual PVA/PANI fibers: 1.2 µm diameter of PANI
nanostructures: <70 nm 		(1) Electrospinning of PVA:
Applied voltage: 10 kV;
Distance to collector: 12 cm;
Solution flow rate: 10 μL/min;
Solution concentration:
7.5 wt% PVA in water
(2) In situ chemical polymerization of aniline on PVA mats		 Electrical conductivity:
2.35 S·cm−1 		No data For fabricating high-performance electrochemical actuators [95]
PANI/gelatin fibers Fiber diameter decreased from 803 ± 121 nm for pure gelatin fibers to 61 ± 13 nm for 60:40 PANI–gelatin blend fibers. Electrospinning of PANI/Gelatin:
Volume ratios of PANI:gelatin were 0:100, 15:85, 30:70, 45:55, and 60:40. The following concentrations (w/v) of the solutions in HFP were 8.00, 6.85, 5.69, 4.54, and 3.38%, respectively.
Applied voltage: 10 kV;
Distance to collector: 10 cm 		Sample with 45:55 ratio of PANI to gelatin;
Tensile strength: 10.49 ± 0.96 MPa;
Elongation at break: 0.09 ± 0.03%;
Tensile modulus: 1384 ± 105 MPa;
Conductivity (S·cm−1):
0.005, 0.01, 0.015, 0.017, and 0.021 for volume ratios of PANI to gelatin of 0:100, 15:85, 30:70, 45:55, and 60:40, respectively		 PANI–gelatin blend fibers supported H9c2 rat cardiac myoblast cell attachment and proliferation to a similar degree as the control tissue culture-treated plastic (TCP) and smooth glass substrates “Intelligent” biomaterials for cardiac and neuronal tissue engineering [98]
SF scaffolds coated with PPy PPy-SF mesh: 80–90 µm thickness (1) Electrospinning of SF:
Needle inner diameter: 0.45 mm;
Applied voltage: +6 kV was applied to the capillary tube and −5 kV to the collector;
Distance to collector: 10 cm;
Solution flow rate: 6.0 mL/h;
Solution concentration: 17 wt/v% in HFIP;
(2) Polymerization of pyrrole on the SF meshes		 Young’s modulus range: 266.7 ± 17.3 MPa for the SF meshes and 310.5 ± 37.6 MPa for the PPy-SF meshes;
Voltametric responses ranging between 10 and 0.5 mV·s–1 		Uncoated and PPy-coated materials support the adherence and proliferation of adult human mesenchymal stem cells (ahMSCs) or human fibroblasts (hFbs) Biocompatible
actuators		 [100]
Nanofibrous PU/PPy Thickness of the PU, PU/PPy-ClO4, PU/PPy-pTS, and PU/PPy-TFSI nanofibers: 10 ± 1, 24 ± 2, 23 ± 2, and 43 ± 3 µm, respectively;
Diameter of PU/PPy nanofibers: 719 ± 74 nm, 571 ± 73 nm, and
556 ± 77 nm, respectively, for ClO4, pTS, and TFSI dopants. 		(1) Electrospinning of PU:
Needle inner diameter: 0.718 mm;
Applied voltage: 14 kV;
Distance to collector: 25 cm;
Solution flow rate: 0.3 mL/h;
Speed of the collector: 5 rps;
Solution concentration: 7 wt/v% in DMF
(2) Polymerization of pyrrole on the PU meshes		 The electrical conductivity of PU/PPy nanofibers produced using ClO4, pTS, and TFSI dopants was measured to be 158, 277, and 315 S·cm−1.
In LiTFSI electrolyte solution, the PU/PPy nanofibrous artificial muscle achieved a bending displacement of 720° in a potential cycle between −0.8 and +0.8 V.		 No data Nanofibrous artificial muscles [102]
PU/PPy-pTS
nanofibers		 Diameter of PU nanofibers: 221 ± 30 nm;
Coated nanofibers: 566 ± 67 nm		 (1) Electrospinning of PU:
Applied voltage: 10, 12, and 14 kV;
Distance to collector: 15, 20, and 25 cm;
Solution flow rate: 0.3 mL/h;
Solution concentration: 7, 8, and 9 wt/v% in DMF
(2) Polymerization of pyrrole and sodium p-TS on the PU meshes 		Conductivity of 276.34 S·cm−1;
Reversible angular displacement capability about of 141°		 No data Artificial muscles [103]
PANI/Au microtubes The inner diameters of PANI/Au microtubes in the range of 1.2–1.5 µm (1) Electrospinning of PMMA:
Applied voltage: 20 kV;
Distance to collector: 17 cm;
Solution flow rate: 0.5 mL/h;
Solution concentration: 10 wt/v% in DMF;
Collector rotation speed: 2000 rpm
(2) Coating fibers with Au
(3) Electrochemical PANI deposition process
(4) Removal of PMMA by immersing in DCM		 By switching the voltage between −0.2 and 1 V, PANI-coated microtubes could reversibly bend No data Artificial muscles [108]
PU/PANI hybrid
nanofibrous bundle		 Diameter of individual hybrid nanofibers in the bundles: about 900 nm;
Average diameter of PU/PANI hybrid nanofibrous bundle: about 90 µm;
Average diameter of PU nanofiber: about 400 nm;
Thickness of PANI coating: about 250 nm		 (1) Electrospinning of PU:
Needle inner diameter: 0.337 mm;
Applied voltage: +7 kV in the capillary tube and −5 kV in the collector;
Distance to collector: 13 cm;
Solution flow rate: 4.0 µL/min;
Solution concentration: 10 wt% in chloroform
(2) In situ chemical polymerization of aniline		 Conductivity of 0.5 S·cm−1 No data Nanofibrous artificial muscles [109]
PVDF with 0.05 wt% and
0.1 wt% BCNW		 Thickness of the
PVDF membrane: 215 µm;
PVDF-BCNW composites: 176 µm and 151 µm, respectively, for 0.05 and 0.1%		 Electrospinning of PVDF:
Needle inner diameter 0.838 mm;
Applied voltage: 12 kV;
Distance to collector: 24 cm;
Solution flow rate: 1.5 mL/h;
Solution concentration: 25 wt% in DMF and acetone (1:1, v/v)		 PVDF/BCNW (0.1 wt%) actuator had a fast response and large tip displacement.
Young’s modulus and yield strength around 3.5 GPa and around 9.5 MPa, respectively.		 No data Actuators
anticipated in the fields of biomimetic robotics, medical devices, various
actuators, and sensors		 [110]
Free-standing
Nylon-6/6 PPy-coated
microribbons		 Widths of the gold-coated electrospun microribbons: 1–1.5 µm;
Thickness of the PPy layer: ~80 nm		 (1) Electrospinning of Nylon-6/6:
Needle inner diameter 0.838 mm;
Applied voltage: 25 kV;
Distance to collector: 15, 20 cm;
Solution flow rate: 0.05–0.10 mL/h;
Solution concentration: 22 wt% in formic acid
(2) Coating of fibers with Au
(3) Electrochemical PPy deposition process		 The fabricated actuator responded by curling and straightening when the external stimulus current, pH, and temperature was applied No data Soft actuators sensing different external stimuli, bifunctional electrochemical devices [111,112]
Au/Nylon-PDMS
- Au covered Nylon-6/6 micrometric fibers attached to a thin PDMS film		 Average diameter of the fibers: 2.08 ± 0.1 µm;
Total thickness of the device: 250 ± 2.5 µm		 (1) Electrospinning of Nylon-6/6:
Needle inner diameter 0.838 mm;
Applied voltage: 20 kV ± 2 kV;
Distance to collector: 15 cm;
Solution flow rate: 0.2 mL/h;
Solution concentration: 30 wt% in formic acid
(2) Coating fibers with Au
(3) Assembly of metalized fiber network to the PDMS sheet 		Displacement of 0.8 cm when applying 2.2 V (500-cycle test performed) No data Artificial muscle [113]
Glucose–gelatin nanofiber scaffolds chemically coated with PPy PPy covered individual fibers separately, resulting in uniformly coated fibers with a similar diameter of 1.58 ± 0.1 µm in aqueous electrolyte and 1.43 ± 0.12 µm in PC electrolyte (1) Electrospinning of glucose/gelatin (in 1:10 wt% ratio, dissolved in 10 M acetic acid):
Applied voltage: 17.5 kV;
Distance to collector: 14.5 cm;
Solution flow rate: 5–7 µL/min;
(2) Crosslinking the nonwovens at 175 °C
(3) Electrochemical PPy deposition process		 PPy coated the CFS fibers showing electrochemomechanical activity in both aqueous and organic (PC) electrolyte solutions;
In water: conductivity: 0.45 ± 0.034 S·cm−1; reversible strain and stress of 1.2% and 3.15 kPa, respectively. 		No data Wearable devices, such as e-skin or in soft robotics devices [114]
Poly(ether-ester-urethane) (PU): poly [4,4′-methylenebis(phenyl isocyanate)-alt-1,4-butanediol/di(propylene glycol)/polycaprolactone] Mean diameter: 0.88 ± 0.36 µm;
Volume fraction: 0.47 ± 0.08;
Bundles were homogeneous (diameters of random bundles 468 ± 33 µm and aligned ones 419 ± 37 µm without the presence of beads)		 Electrospinning of PU:
Four needles with inner diameter of 0.51 mm;
Applied voltage: 23 kV;
Distance to collector: 18 cm;
Solution flow rate: 0.3 mL/h;
Solution concentration:
25 w/v in THF:DMF (70:30, v/v)
collector, with a speed of 1500 mm min–1 		A failure force of the random mats:
FF = 0.83 ± 0.08 N (εF = 232 ± 17%);
Of bundles:
FF = 0.50 ± 0.08 N (εF = 182 ± 18%)		 No data Muscle tissue engineering and soft actuators [115]
RM 257 as a liquid crystal mesogen and HDT as a chain extender doped with PDA The diameters of microfibers ranged from 10 to 100 µm (1) Electrospinning of ink (RM257, HDT, HHMP):
Four needles with inner diameters of 1.194 mm;
Applied voltage: 6 kV;
Solution flow rate: 0.02 mL/min;
Solution concentration: 20 wt% in TCM
During the electrospinning process, the LCE microfibers were exposed to UV light (365 nm wavelength) to trigger the crosslinking reaction
(2) Preparation of PDA-coated LCE microfibers through a simple dip-coating process		 Longitudinal contraction under the exposure of NIR light of PDA-LCE;
Actuation strain: >50%; actuation stress: 0.3 MPa; response speed: 300%/s; and work density: 20 kJ/m3
The temperature actuation strains were 55, 33, and 30% at 120 °C when the applied stresses were 0.02, 0.08, and 0.16 MPa, respectively		 No data LCE microfiber actuator for artificial muscles, microrobots, or microfluidic pumps. [116]

Abbreviations: CA: cellulose acetate; PANI: polyaniline; PVA: poly(vinyl alcohol); NGF: nerve growth factor; PLCL: poly[(L-lactide)-co-(ε-caprolactone)]; SF: silk fibroin; PEDOT: poly(3,4-ethylenodioxythiophene); PVP: polyvinylpyrrolidone; EDOT: 3,4-ethylenedioxythiophene; PPy: polypyrrole; p-TS: p-toluenesulfonate; PU: polyurethane; PMMA: poly(methyl methacrylate); BCNW: bacterial cellulose nanowhiskers; PDMS: polydimethylsiloxane, HDT: hexane dithiol; HHMP: (2-hydroxyethoxy)-2-methylpropiophenone; DPA: polydopami.