Table 2.
Summary of selected micro- and nanorobots for water remediation
Robot | Fabrication method | Size | Motion mechanism | Pollutant | Adsorption and degradation mechanism | Efficiency | Ref. |
---|---|---|---|---|---|---|---|
Nano- and microplastics | |||||||
Au–Ni–TiO2 | Chemical | 700 nm | UV light | Microplastics (personal-care products in the Baltic sea) | Phoretic interactions and shovelling | 67% in 40 s | 101 |
Ni–SPGs | Biotemplated | ∼30 μm | Magnetic | Polystyrene beads | Non-contact shovelling | ∼75% | 113 |
Fe2O3–MnO2 | Hydrothermal and annealing | ∼5 μm | Bubble propulsion | Microplastics (personal-care products) | Adsorptive bubble separation | ∼10% in 2 h | 114 |
Bi2WO6 | Hydrothermal | ∼7 μm | Visible light | Textile fibres | Photocatalysis | 50 h | 115 |
Fe3O4–BiVO4 | Hydrothermal | 4–8 μm | Visible light and magnetic | Polylactic acid, PCL, PET, polypropylene | Precipitation and photocatalysis | ∼3% in 7 days | 116 |
Lipase–PDA–Fe3O4 | Chemical | Micrometre-scale | Magnetic | PCL | Chemical adhesion and enzymatic | 24 h | 100 |
Pt–Pd–Fe2O3 | Hydrothermal and sputtering | 3–4 μm | UV light and magnetic | PEG | Electrostatic and photo-Fenton | ∼100% in 24 h | 117 |
Organic molecules | |||||||
OPH-microbead rotifers | Bio-hybrid | 100–300 μm | Cilia | Methyl paraoxon | Enzymatic | NR | 129 |
Polypyrrole–Fe3O4–Pt | Electrochemical | ∼10 μm | Bubble propulsion and magnetic | α-Oestradiol | Electrostatic and weaving of macroscopic webs | NR | 130 |
Polyurethane sponge–CFO | Chemical | Millimetre-scale | Bubble propulsion and magnetic | Methylene blue | Fenton-like | 90% in 20 min | 132 |
PEDOT–polypyrrole-COOH–Pt | Electrochemical | ∼10 μm | Bubble propulsion | Dyes | Enzymatic | 76–94% in 10 min | 134 |
MIP PINIPAM-Mn3O4–CoFe2O4 | Bio-templated | 50 μm | Bubble propulsion and magnetic | Erythromycin | Hydrogen bonding and hydrophobic interactions | 98% in 1 h | 137 |
Pt–TiO2 into a 3D-printed robot | 3D printing | Millimetre-scale | Marangoni effect | Picric acid | Photocatalysis | 6 h | 138 |
Heavy metals | |||||||
Pt–nanoclay | Sputtering | ∼700 nm | Bubble propulsion | Zn2+ and Cd2+ | Electrostatic | ∼86% in 5 min | 144 |
Fe3O4–MnO2–MHMs | Biotemplated | ∼100 μm | Magnetic | Pb2+ | Adsorption | 99% | 147 |
C3N4 | Hydrothermal and annealing | 50–80 μm | Visible light | Cu2+ | Complex formation with N and C functional groups | 50% in 7 min | 148 |
Fe3O4–Fe–ZIF8-Pt | Chemical | ∼10 μm | Bubble propulsion and magnetic | UO22+ | Adsorption | >97% in 1 h | 151 |
MMSNBs | Chemical | ∼300 nm | Enzymatic and magnetic | Cu2+ | Adsorption | 80% in 1 h | 150 |
pAsp–Ni–Pt (pCys–Ni–Pt) | Electrochemical | ∼15 μm | Bubble propulsion and magnetic | Cd2+ (CH3ClHg) | Electrostatic (covalent complex formation) | ∼100% in 4 min | 153 |
T–T mismatched DNA–Au–Pt | Electrochemical | ∼10 μm | Bubble propulsion | Hg2+ | T–Hg2+–T complex formation | 26% in 20 min | 154 |
Pt–MIMs | Chemical and sputtering | ∼20 μm | Bubble propulsion | 137Cs | Adsorption | ∼99% in 1 h | 156 |
PTBC–TM-Fe3O4 | Chemical | ∼200 nm | Magnetic | As | Adsorption | ∼68% in 100 min | 157 |
nGF–Ni–Pt (Bi–Ni–Pt) | Electrochemical | ∼12 μm | Bubble propulsion and magnetic | Li+, Mg2+ (Na+, Ca2+) | Intercalation | 5 min | 158 |
Oil spills | |||||||
Fe3O4–Ag–pETPTA | Emulsion | ∼475 μm | Bubble propulsion | Oil mixture | Hydrophobic interactions | 10 min | 162 |
Catalase–Fe3O4–PCL | Chemical | ∼14 μm | Enzymatic and magnetic | Oil mixture | Hydrophobic interactions | ∼75% in 1 h | 163 |
PDA–Fe3O4–PFDT | Chemical | Millimetre-scale | Magnetic | DCM, Chl, toluene | Chemical adhesion | 5 min | 164 |
Lipase–MSNPs | Chemical | 431 nm | Enzymatic | Tributyrin | Enzymatic | 100% in 1 h | 165 |
Microorganisms | |||||||
CARs | 3D micromoulding | Millimetre-scale | Catalytic and magnetic | Bacterial biofilm | Physical erosion and degradation | NR | 174 |
T-Budbots | Biotemplated | 50–160 μm | Magnetic | Bacterial biofilm | Kill-n-clean | 50% | 109 |
Iron oxide MHMs | Biotemplated | 34 μm | Magnetic | Escherichia coli | Photothermal | ∼99% in 6 min | 175 |
Ag-doped ZnO | Hydrothermal | ∼5 μm | UV light | Bacterial biofilm | Ag+ release and photocatalysis | ∼90% in 5 min | 105 |
BiVO4 | Hydrothermal | 4–8 μm | Visible light | Saccharomyces cerevisiae | Photocatalysis | ∼40% in 2 h | 177 |
ACE2 algae | Biohybrid | ∼1 µm | Self-propulsion | SARS-CoV-2 spike protein | Enzymatic | ∼99% in 16 h | 178 |
ACE2, angiotensin-converting enzyme 2; CAR, catalytic antimicrobial robot; CFO, cobalt ferrite; MHM, magnetic helical microrobot; MIMS, magnetic illite microsphere; MIP, molecularly imprinted polymer; MMSNB, multilayer-sandwich magnetic mesoporous silica nanobottle; MP, microplastic; MSNP, mesoporous silica nanoparticle; nGF, graphite nanofibre; NR, not reported; OPH, organophosphorus hydrolase; pAsp, polyaspartic acid; PCL, polycaprolactone; pCys, polycysteine; PDA, polydopamine; PEDOT, poly(3,4-ethylenedioxythiophene); PEG, polyethylene glycol; PET, polyethylene terephthalate; pETPTA, poly(ethoxylated trimethylolpropane triacylate); PFDT, 1H,1H,2H,2H-perfluorodecanethiol; PNIPAM, poly(N-isopropylacrylamide); PTBC–TM, pluronic tri-block copolymer-thermoresponsive; SPG, sunflower pollen grain; UV, ultraviolet; ZIF, zeolitic imidazolate framework.