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Table 1 Classification of additives, polymers, and required stimuli of the hydrogel actuators and actuation comparisons in terms of their maximum deformability, response speed, and response efficiency

From: Nanocomposite hydrogel actuators hybridized with various dimensional nanomaterials for stimuli responsiveness enhancement

Dimensions

Material

Polymer

Stimuli source

Release energy

Maximum deformability

Response speed

Response efficiency

Refs.

Zero dimension (0D)

Gold nanoparticle and nanoshell (AuNP and AuNS)

Poly(N-isopropylacrylamide) (PNIPAAm)

Near Infrared light (NIR)

Heat

4.28 cm−1 [46]

5 s [35], 25 s [42], 20 min [46]

[35, 42, 46]

 

Iron oxide nanoparticle (IONP)

PNIPAAm

Alternating magnetic field (AMF)

Heat

[46]

  

Acrylamide (AAm)

Magnet

 

0.9 cm−1

[37]

 

Ytterbium and neodium

PNIPAAm

808 and 980 nm light irradiation

Heat

45° bending

< 10 s

[39]

 

Poly(dopamine) nanoparticle

PNIPAAm

MR light

Heat

30 s

77%

[40]

One dimension (ID)

Nanofibrillated cellulose

N,N-dimethylacrylamide

Hydration/dehydration

    

[50]

Thermoplastic urethane (TPU)

PNIPAAm

Temperature change

 

0.6 s

[51]

Carbon nanotube (CNT)

PNIPAAm

Temperature change

 

90° bending

~ 2.7 s

[52]

Multiwall carbon nanotube (MWCNT)

Polyvinylalcohol (PVA)

Electric field

Heat

58° bending

30 s

[53]

Two dimension (2D)

Reduced graphene oxide (rGO)

Elastin-like polypeptide (ELP)

NIR light

 

60° bending

3 s

[57]

Poly(2-acrylamido-2-methyl-propanesulfonic

Electric field

Heat

0.088 mm−1

12 s

[58]

Graphene oxide (GO)

PNIPAAm

NIR light

 

300° bending

40 s

[59]

Titanate nanosheet (TINS)

PNIPAAm

Temperature change

Heat

170% elongation

In a second

~ 70% s−1

[60]

TiNS + AuNP

PNIPAAm

NIR light

Heat

180% elongation

< 0.5 s

[72]

Transition metal dicalchogenide (TMD)

PNIPAAm

NIR light

 

0.22 mm−1 [62]

70 s [62]

[61, 62]

Fluorohectorite (FHT)

PNIPAAm

Temperature change

 

130%

5.6 s

[63]