Two-photon polymerization-based 4D printing and its applications

Jadhav A and Jadhav V S 2022 A review on 3D printing: an additive manufacturing technology Mater. Today Proc. 62 2094–9

Ge Q, Li Z Q, Wang Z L, Kowsari K, Zhang W, He X N, Zhou J L and Fang N X 2020 Projection micro stereolithography based 3D printing and its applications Int. J. Extrem. Manuf. 2 022004

O’Halloran S, Pandit A, Heise A and Kellett A 2023 Two-photon polymerization: fundamentals, materials, and chemical modification strategies Adv. Sci. 10 2204072

Harinarayana V and Shin Y C 2021 Two-photon lithography for three-dimensional fabrication in micro/nanoscale regime: a comprehensive review Opt. Laser Technol. 142 107180

Rad Z F, Prewett P D and Davies G J 2021 High-resolution two-photon polymerization: the most versatile technique for the fabrication of microneedle arrays Microsyst. Nanoeng. 7 71

Li J H and Pumera M 2021 3D printing of functional microrobots Chem. Soc. Rev. 50 2794–838

Weiß T, Hildebrand G, Schade R and Liefeith K 2009 Two-photon polymerization for microfabrication of three-dimensional scaffolds for tissue engineering application Eng. Life Sci. 9 384–90

Lin Y and Xu J 2018 Microstructures fabricated by two-photon polymerization and their remote manipulation techniques: toward 3D printing of micromachines Adv. Opt. Mater. 6 1701359

Mayer F, Richter S, Westhauser J, Blasco E, Barner-Kowollik C and Wegener M 2019 Multimaterial 3D laser microprinting using an integrated microfluidic system Sci. Adv. 5 eaau9160

Momeni F, Hassani N S M M, Liu X and Ni J 2017 A review of 4D printing Mater. Des. 122 42–79

Ge Q, Qi H J and Dunn M L 2013 Active materials by four-dimension printing Appl. Phys. Lett. 103 131901

Ge Q, Dunn C K, Qi H J and Dunn M L 2014 Active origami by 4D printing Smart Mater. Struct. 23 094007

Ge Q, Sakhaei A H, Lee H, Dunn C K, Fang N X and Dunn M L 2016 Multimaterial 4D printing with tailorable shape memory polymers Sci. Rep. 6 31110

Yuan C, Wang F F and Ge Q 2021 Multimaterial direct 4D printing of high stiffness structures with large bending curvature Extreme Mech. Lett. 42 101122

Yang H, Leow W R, Wang T, Wang J, Yu J C, He K, Qi D P, Wan C J and Chen X D 2017 3D printed photoresponsive devices based on shape memory composites Adv. Mater. 29 1701627

Bai Y K, Zhang J W and Chen X 2018 A thermal-, water-, and near-infrared light-induced shape memory composite based on polyvinyl alcohol and polyaniline fibers ACS Appl. Mater. Interfaces 10 14017–25

Shanthamma S, Preethi R, Moses J A and Anandharamakrishnan C 2021 4D printing of sago starch with turmeric blends: a study on pH-triggered spontaneous color transformation ACS Food Sci. Technol. 1 669–79

Chen H M, Li Y, Liu Y, Gong T, Wang L and Zhou S B 2014 Highly pH-sensitive polyurethane exhibiting shape memory and drug release Polym. Chem. 5 5168–74

Gladman A S, Matsumoto E A, Nuzzo R G, Mahadevan L and Lewis J A 2016 Biomimetic 4D printing Nat. Mater. 15 413–8

Raviv D et al 2014 Active printed materials for complex self-evolving deformations Sci. Rep. 4 7422

Kim Y, Yuk H, Zhao R K, Chester S A and Zhao X H 2018 Printing ferromagnetic domains for untethered fast-transforming soft materials Nature 558 274–9

Dong Y, Wang L, Xia N, Yang Z X, Zhang C, Pan C F, Jin D D, Zhang J C, Majidi C and Zhang L 2022 Untethered small-scale magnetic soft robot with programmable magnetization and integrated multifunctional modules Sci. Adv. 8 eabn8932

Yousuf M H, Abuzaid W and Alkhader M 2020 4D printed auxetic structures with tunable mechanical properties Addit. Manuf. 35 101364

Wang Z J, Wang Z J, Zheng Y, He Q G, Wang Y and Cai S Q 2020 Three-dimensional printing of functionally graded liquid crystal elastomer Sci. Adv. 6 eabc0034

Qu J Y, Kadic M, Naber A and Wegener M 2017 Micro-structured two-component 3D metamaterials with negative thermal-expansion coefficient from positive constituents Sci. Rep. 7 40643

Hann S Y, Cui H T, Nowicki M and Zhang L G 2020 4D printing soft robotics for biomedical applications Addit. Manuf. 36 101567

Ge Q et al 2021 3D printing of highly stretchable hydrogel with diverse UV curable polymers Sci. Adv. 7 eaba4261

He X et al 2023 Multimaterial three-dimensional printing of ultraviolet-curable ionic conductive elastomers with diverse polymers for multifunctional flexible electronics ACS Appl. Mater. Interfaces 15 3455–66

He X N, Cheng J X, Li Z Q, Ye H T, Sun Z C, Liu Q J, Li H G, Wang R and Ge J 2023 Stretchable ultraviolet curable ionic conductive elastomers for digital light processing based 3D printing Adv. Mater. Technol. 8 2202088

Rajabasadi F, Schwarz L, Medina-Sánchez M and Schmidt O G 2021 3D and 4D lithography of untethered microrobots Prog. Mater. Sci. 120 100808

Zhang B et al 2021 Mechanically robust and UV-curable shape-memory polymers for digital light processing based 4D printing Adv. Mater. 33 2101298

Adam G, Benouhiba A, Rabenorosoa K, Clévy C and Cappelleri D J 2021 4D printing: enabling technology for microrobotics applications Adv. Intell. Syst. 3 2000216

Ouyang W Q, Xu X Y, Lu W P, Zhao N, Han F and Chen S-C 2023 Ultrafast 3D nanofabrication via digital holography Nat. Commun. 14 1716

Geng Q, Wang D E, Chen P F and Chen S-C 2019 Ultrafast multi-focus 3D nano-fabrication based on two-photon polymerization Nat. Commun. 10 2179

Tottori S, Zhang L, Qiu F M, Krawczyk K K, Franco-Obregón A and Nelson B J 2012 Magnetic helical micromachines: fabrication, controlled swimming, and cargo transport Adv. Mater. 24 811–6

Huang T-Y, Sakar M S, Mao A, Petruska A J, Qiu F M, Chen X-B, Kennedy S, Mooney D and Nelson B J 2015 3D printed microtransporters: compound micromachines for spatiotemporally controlled delivery of therapeutic agents Adv. Mater. 27 6644–50

Watanabe T, Akiyama M, Totani K, Kuebler S M, Stellacci F, Wenseleers W, Braun K, Marder S R and Perry J W 2002 Photoresponsive hydrogel microstructure fabricated by two-photon initiated polymerization Adv. Funct. Mater. 12 611–4

Kaehr B and Shear J B 2008 Multiphoton fabrication of chemically responsive protein hydrogels for microactuation Proc. Natl Acad. Sci. USA 105 8850–4

McCracken J M et al 2019 Microstructured photopolymerization of liquid crystalline elastomers in oxygen-rich environments Adv. Funct. Mater. 29 1903761

Carlotti M, Tricinci O, den Hoed F, Palagi S and Mattoli V 2021 Direct laser writing of liquid crystal elastomers oriented by a horizontal electric field Open Res. Eur. 1 129

Guo Y B, Shahsavan H and Sitti M 2020 Microscale polarization color pixels from liquid crystal elastomers Adv. Opt. Mater. 8 1902098

Lay C L, Koh C S L, Lee Y H, Phan-Quang G C, Sim H Y F, Leong S X, Han X M, Phang I Y and Ling X Y 2020 Two-photon-assisted polymerization and reduction: emerging formulations and applications ACS Appl. Mater. Interfaces 12 10061–79

Nguyen A K and Narayan R J 2017 Two-photon polymerization for biological applications Mater. Today 20 314–22

Naniz M A, Askari M, Zolfagharian A, Naniz M A and Bodaghi M 2022 4D printing: a cutting-edge platform for biomedical applications Biomed. Mater. 17 062001

Willemen N G A, Morsink M A J, Veerman D, da Silva C F, Cardoso J C, Souto E B and Severino P 2022 From oral formulations to drug-eluting implants: using 3D and 4D printing to develop drug delivery systems and personalized medicine Bio-Des. Manuf. 5 85–106

Del Pozo M, Delaney C, da Cunha M P, Debije M G, Florea L and Schenning A P H J 2022 Temperature-responsive 4D liquid crystal microactuators fabricated by direct laser writing by two-photon polymerization Small Struct. 3 2100158

Zhang W et al 2021 Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers Nat. Commun. 12 112

Yasa I C, Ceylan H, Bozuyuk U, Wild A-M and Sitti M 2020 Elucidating the interaction dynamics between microswimmer body and immune system for medical microrobots Sci. Robot. 5 eaaz3867

Cabanach P, Pena-francesch A, Sheehan D, Bozuyuk U, Yasa O, Borros S and Sitti M 2020 Zwitterionic 3D-printed non-immunogenic stealth microrobots Adv. Mater. 32 2003013

Zeng H, Wasylczyk P, Parmeggiani C, Martella D, Burresi M and Wiersma D S 2015 Light-fueled microscopic walkers Adv. Mater. 27 3883–7

Spiegel C A, Hippler M, Münchinger A, Bastmeyer M, Barner-kowollik C, Wegener M and Blasco E 2020 4D printing at the microscale Adv. Funct. Mater. 30 1907615

Wang H et al 2023 Two-photon polymerization lithography for optics and photonics: fundamentals, materials, technologies, and applications Adv. Funct. Mater. 33 2214211

Ovsianikov A et al 2008 Ultra-low shrinkage hybrid photosensitive material for two-photon polymerization microfabrication ACS Nano 2 2257–62

Spiegel C A, Hackner M, Bothe V P, Spatz J P and Blasco E 2022 4D printing of shape memory polymers: from macro to micro Adv. Funct. Mater. 32 2110580

Göppert-Mayer M 1931 Über elementarakte mit zwei quantensprüngen Ann. Phys. 401 273–94

Kaiser W and Garrett C G B 1961 Two-photon excitation in CaF₂: Eu²⁺ Phys. Rev. Lett. 7 229–31

Denk W, Strickler J H and Webb W W 1990 Two-photon laser scanning fluorescence microscopy Science 248 73–76

Maruo S, Nakamura O and Kawata S 1997 Three-dimensional microfabrication with two-photon-absorbed photopolymerization Opt. Lett. 22 132–4

Samsonas D et al 2023 3D nanopolymerization and damage threshold dependence on laser wavelength and pulse duration Nanophotonics 12 1537–48

Butkus A, Skliutas E, Gailevičius D and Malinauskas M 2022 Femtosecond-laser direct writing 3D micro/nano-lithography using VIS-light oscillator J. Cent. South Univ. 29 3270–6

Kawata S, Sun H-B, Tanaka T and Takada K 2001 Finer features for functional microdevices Nature 412 697–8

Desbiolles B X E, Bertsch A and Renaud P 2019 Ion beam etching redeposition for 3D multimaterial nanostructure manufacturing Microsyst. Nanoeng. 5 11

Somers P, Liang Z H, Johnson J E, Boudouris B W, Pan L and Xu X F 2021 Rapid, continuous projection multi-photon 3D printing enabled by spatiotemporal focusing of femtosecond pulses Light Sci. Appl. 10 199

Hahn V, Messer T, Bojanowski N M, Curticean E R, Wacker I, Schröder R R, Blasco E and Wegener M 2021 Two-step absorption instead of two-photon absorption in 3D nanoprinting Nat. Photon. 15 932–8

Hahn V, Rietz P, Hermann F, Müller P, Barner-Kowollik C, Schlöder T, Wenzel W, Blasco E and Wegener M 2022 Light-sheet 3D microprinting via two-colour two-step absorption Nat. Photon. 16 784–91

Gissibl T, Thiele S, Herkommer A and Giessen H 2016 Two-photon direct laser writing of ultracompact multi-lens objectives Nat. Photon. 10 554–60

Rad Z F, Nordon R E, Anthony C J, Bilston L, Prewett P D, Arns J-Y, Arns C H, Zhang L C and Davies G J 2017 High-fidelity replication of thermoplastic microneedles with open microfluidic channels Microsyst. Nanoeng. 3 17034

Sugioka K and Cheng Y 2014 Femtosecond laser three-dimensional micro-and nanofabrication Appl. Phys. Rev. 1 041303

Saha S K, Wang D E, Nguyen V H, Chang Y N, Oakdale J S and Chen S-C 2019 Scalable submicrometer additive manufacturing Science 366 105–9

Maibohm C, Silvestre O F, Borme J, Sinou M, Heggarty K and Nieder J B 2020 Multi-beam two-photon polymerization for fast large area 3D periodic structure fabrication for bioapplications Sci. Rep. 10 8740

Yang L L, Wei J T, Ma Z, Song P S, Ma J, Zhao Y Q, Huang Z, Zhang M L, Yang F H and Wang X D 2019 The fabrication of micro/nano structures by laser machining Nanomaterials 9 1789

Coelho S, Baek J, Walsh J, Justin Gooding J and Gaus K 2022 Direct-laser writing for subnanometer focusing and single-molecule imaging Nat. Commun. 13 647

Sedghamiz E, Liu M D and Wenzel W 2022 Challenges and limits of mechanical stability in 3D direct laser writing Nat. Commun. 13 2115

Rad Z F, Prewett P D and Davies G J 2022 Parametric optimization of two-photon direct laser writing process for manufacturing polymeric microneedles Addit. Manuf. 56 102953

Balena A, Bianco M, Pisanello F and De Vittorio M 2023 Recent advances on high-speed and holographic two-photon direct laser writing Adv. Funct. Mater. 33 2211773

Gonzalez-hernandez D, Sanchez-padilla B, Gailevičius D, Thodika S C, Juodkazis S, Brasselet E and Malinauskas M 2023 Single-step 3D printing of micro-optics with adjustable refractive index by ultrafast laser nanolithography Adv. Opt. Mater. 11 2300258

Wloka T, Gottschaldt M and Schubert U S 2022 From light to structure: photo initiators for radical two-photon polymerization Chem. Eur. J. 28 e202104191

Carlotti M and Mattoli V 2019 Functional materials for two-photon polymerization in microfabrication Small 15 1902687

Tičkūnas T, Perrenoud M, Butkus S, Gadonas R, Rekštytė S M, Malinauskas M, Paipulas D, Bellouard Y and Sirutkaitis V 2017 Combination of additive and subtractive laser 3D microprocessing in hybrid glass/polymer microsystems for chemical sensing applications Opt. Express 25 26280–8

Peters C, Ergeneman O, García P D W, Müller M, Pané S, Nelson B J and Hierold C 2014 Superparamagnetic twist-type actuators with shape-independent magnetic properties and surface functionalization for advanced biomedical applications Adv. Funct. Mater. 24 5269–76

Wang X P et al 2019 MOFBOTS: metal-organic-framework-based biomedical microrobots Adv. Mater. 31 1901592

Qiu F M, Zhang L, Peyer K E, Casarosa M, Franco-Obregón A, Choi H and Nelson B J 2014 Noncytotoxic artificial bacterial flagella fabricated from biocompatible ORMOCOMP and iron coating J. Mater. Chem. B 2 357–62

Schwarz L, Karnaushenko D D, Hebenstreit F, Naumann R, Schmidt O G and Medina-sánchez M 2020 A rotating spiral micromotor for noninvasive zygote transfer Adv. Sci. 7 2000843

Yang L et al 2019 Targeted single-cell therapeutics with magnetic tubular micromotor by one-step exposure of structured femtosecond optical vortices Adv. Funct. Mater. 29 1905745

Xin C et al 2019 Conical hollow microhelices with superior swimming capabilities for targeted cargo delivery Adv. Mater. 31 1808226

Villangca M J, Palima D, Bañas A R and Glückstad J 2016 Light-driven micro-tool equipped with a syringe function Light Sci. Appl. 5 e16148

Liu X J, Wei M X, Wang Q, Tian Y J, Han J M, Gu H C, Ding H B, Chen Q, Zhou K and Gu Z Z 2021 Capillary-force-driven self-assembly of 4D-printed microstructures Adv. Mater. 33 2100332

Rekštytė S, Paipulas D, Malinauskas M and Mizeikis V 2017 Microactuation and sensing using reversible deformations of laser-written polymeric structures Nanotechnology 28 124001

Minnick G et al 2023 Two-photon polymerized shape memory microfibers: a new mechanical characterization method in liquid Adv. Funct. Mater. 33 2206739

Zyla G, Kovalev A, Gurevich E L, Esen C, Liu Y, Lu Y F, Gorb S and Ostendorf A 2020 Structural colors with angle-insensitive optical properties generated by Morpho-inspired 2PP structures Appl. Phys. A 126 740

Elliott L V, Salzman E E and Greer J R 2021 Stimuli responsive shape memory microarchitectures Adv. Funct. Mater. 31 2008380

Zhang W et al 2022 Stiff shape memory polymers for high-resolution reconfigurable nanophotonics Nano Lett. 22 8917–24

Ceylan H, Yasa I C, Yasa O, Tabak A F, Giltinan J and Sitti M 2019 3D-printed biodegradable microswimmer for theranostic cargo delivery and release ACS Nano 13 3353–62

Sun H C M, Liao P, Wei T Y, Zhang L and Sun D 2020 Magnetically powered biodegradable microswimmers Micromachines 11 404

Park J, Jin C, Lee S, Kim J-Y and Choi H 2019 Magnetically actuated degradable microrobots for actively controlled drug release and hyperthermia therapy Adv. Healthcare Mater. 8 1900213

Wang X P, Qin X-H, Hu C Z, Terzopoulou A, Chen X-Z, Huang T-Y, Maniura-weber K, Pané S and Nelson B J 2018 3D printed enzymatically biodegradable soft helical microswimmers Adv. Funct. Mater. 28 1804107

Bozuyuk U, Yasa O, Yasa I C, Ceylan H, Kizilel S and Sitti M 2018 Light-triggered drug release from 3D-printed magnetic chitosan microswimmers ACS Nano 12 9617–25

Jin D D, Chen Q Y, Huang T-Y, Huang J Y, Zhang L and Duan H L 2020 Four-dimensional direct laser writing of reconfigurable compound micromachines Mater. Today 32 19–25

Huang T-Y, Huang H-W, Jin D D, Chen Q Y, Huang J Y, Zhang L and Duan H L 2020 Four-dimensional micro-building blocks Sci. Adv. 6 eaav8219

Chen Q Y, Lv P Y, Huang T-Y, Huang J Y and Duan H L 2020 Encoding smart microjoints for microcrawlers with enhanced locomotion Adv. Intell. Syst. 2 1900128

Ma Z-C, Zhang Y-L, Han B, Hu X-Y, Li C-H, Chen Q-D and Sun H-B 2020 Femtosecond laser programmed artificial musculoskeletal systems Nat. Commun. 11 4536

Wang J-Y, Jin F, Dong X-Z, Liu J and Zheng M-L 2022 Flytrap inspired pH-driven 3D hydrogel actuator by femtosecond laser microfabrication Adv. Mater. Technol. 7 2200276

Hu Y et al 2020 Botanical-inspired 4D printing of hydrogel at the microscale Adv. Funct. Mater. 30 1907377

Wei S X, Liu J, Zhao Y Y, Zhang T B, Zheng M L, Jin F, Dong X Z, Xing J F and Duan X M 2017 Protein-based 3D microstructures with controllable morphology and pH-responsive properties ACS Appl. Mater. Interfaces 9 42247–57

Li R et al 2020 Stimuli-responsive actuator fabricated by dynamic asymmetric femtosecond bessel beam for in situ particle and cell manipulation ACS Nano 14 5233–42

Wang J G, Zhang Y Z, Zheng J C, Zhao X B, Guo H J, Qiu Y, Wang X D, Liu L Q and Yu H B 2023 A 4D-printing inverse design strategy for micromachines with customized shape-morphing Small 2302656

Deng C S, Liu Y C, Fan X H, Jiao B Z, Zhang Z X, Zhang M D, Chen F Y, Gao H, Deng L M and Xiong W 2023 Femtosecond laser 4D printing of light-driven intelligent micromachines Adv. Funct. Mater. 33 2211473

Hippler M, Blasco E, Qu J Y, Tanaka M, Barner-Kowollik C, Wegener M and Bastmeyer M 2019 Controlling the shape of 3D microstructures by temperature and light Nat. Commun. 10 232

Spratte T, Geiger S, Colombo F, Mishra A, Taale M, Hsu L-Y, Blasco E and Selhuber-unkel C 2023 Increasing the efficiency of thermoresponsive actuation at the microscale by direct laser writing of pNIPAM Adv. Mater. Technol. 8 2200714

Liu Y C, Liu R C, Qiu J J and Wang S R 2022 4D printing of thermal responsive structure for environmentally adaptive radiative cooling and heating J. Adv. Manuf. Process. 4 e10107

Tudor A, Delaney C, Zhang H R, Thompson A J, Curto V F, Yang G-Z, Higgins M J, Diamond D and Florea L 2018 Fabrication of soft, stimulus-responsive structures with sub-micron resolution via two-photon polymerization of poly(ionic liquid)s Mater. Today 21 807–16

Zhang Y-L, Tian Y, Wang H, Ma Z-C, Han D-D, Niu L-G, Chen Q-D and Sun H-B 2019 Dual-3D femtosecond laser nanofabrication enables dynamic actuation ACS Nano 13 4041–8

Ennis A, Nicdao D, Kolagatla S, Dowling L, Tskhe Y, Thompson A J, Trimble D, Delaney C and Florea L 2023 Two-photon polymerization of sugar responsive 4D microstructures Adv. Funct. Mater. 33 2213947

Lv C et al 2018 Humidity-responsive actuation of programmable hydrogel microstructures based on 3D printing Sens. Actuators B 259 736–44

Guo Y B, Zhang J C, Hu W Q, Khan M T A and Sitti M 2021 Shape-programmable liquid crystal elastomer structures with arbitrary three-dimensional director fields and geometries Nat. Commun. 12 5936

Del Pozo M, Delaney C, Bastiaansen C W M, Diamond D, Schenning A P H J and Florea L 2020 Direct laser writing of four-dimensional structural color microactuators using a photonic photoresist ACS Nano 14 9832–9

Martella D, Nocentini S, Nuzhdin D, Parmeggiani C and Wiersma D S 2017 Photonic microhand with autonomous action Adv. Mater. 29 1704047

Münchinger A, Hsu L-Y, Fürniß F, Blasco E and Wegener M 2022 3D optomechanical metamaterials Mater. Today 59 9–17

Chen L, Dong Y Q, Tang C-Y, Zhong L, Law W-C, Tsui G C P, Yang Y K and Xie X L 2019 Development of direct-laser-printable light-powered nanocomposites ACS Appl. Mater. Interfaces 11 19541–53

Hsu L-Y, Mainik P, Münchinger A, Lindenthal S, Spratte T, Welle A, Zaumseil J, Selhuber-unkel C, Wegener M and Blasco E 2023 A facile approach for 4D microprinting of multi-photoresponsive actuators Adv. Mater. Technol. 8 2200801

Zhang C Q, Li X J, Jiang L M, Tang D F, Xu H, Zhao P, Fu J Z, Zhou Q F and Chen Y 2021 3D printing of functional magnetic materials: from design to applications Adv. Funct. Mater. 31 2102777

Zhou H J, Mayorga-Martinez C C, Pané S, Zhang L and Pumera M 2021 Magnetically driven micro and nanorobots Chem. Rev. 121 4999–5041

Peyer K E, Tottori S, Qiu F M, Zhang L and Nelson B J 2013 Magnetic helical micromachines Chem. Eur. J. 19 28–38

Chen X-Z, Hoop M, Mushtaq F, Siringil E, Hu C Z, Nelson B J and Pané S 2017 Recent developments in magnetically driven micro- and nanorobots Appl. Mater. Today 9 37–48

Liu D, Guo R R, Wang B, Hu J W and Lu Y 2022 Magnetic micro/nanorobots: a new age in biomedicines Adv. Intell. Syst. 4 2200208

Khalid M Y, Arif Z U, Noroozi R, Zolfagharian A and Bodaghi M 2022 4D printing of shape memory polymer composites: a review on fabrication techniques, applications, and future perspectives J. Manuf. Process. 81 759–97

Champeau M, Heinze D A, Viana T N, De Souza E R, Chinellato A C and Titotto S 2020 4D printing of hydrogels: a review Adv. Funct. Mater. 30 1910606

Dong Y T, Wang S C, Ke Y J, Ding L C, Zeng X T, Magdassi S and Long Y 2020 4D printed hydrogels: fabrication, materials, and applications Adv. Mater. Technol. 5 2000034

Chen M, Gao M, Bai L C, Zheng H, Qi H J and Zhou K 2023 Recent advances in 4D printing of liquid crystal elastomers Adv. Mater. 35 2209566

Del Pozo M, Sol J A H P, Schenning A P H J and Debije M G 2022 4D printing of liquid crystals: what's right for me? Adv. Mater. 34 2104390

Zeng H, Martella D, Wasylczyk P, Cerretti G, Lavocat J C G, Ho C H, Parmeggiani C and Wiersma D S 2014 High-resolution 3D direct laser writing for liquid-crystalline elastomer microstructures Adv. Mater. 26 2319–22

Wang L C, Meng Z Y, Chen Y and Zheng Y Y 2021 Engineering magnetic micro/nanorobots for versatile biomedical applications Adv. Intell. Syst. 3 2000267

Wang X Y, Wei Z P, Baysah C Z, Zheng M L and Xing J F 2019 Biomaterial-based microstructures fabricated by two-photon polymerization microfabrication technology RSC Adv. 9 34472–80

Luo M, Feng Y Z, Wang T W and Guan J G 2018 Micro-/nanorobots at work in active drug delivery Adv. Funct. Mater. 28 1706100

Sun Z L and Hou Y L 2022 Micro/nanorobots as active delivery systems for biomedicine: from self-propulsion to controllable navigation Adv. Ther. 5 2100228

Soto F, Wang J, Ahmed R and Demirci U 2020 Medical micro/nanorobots in precision medicine Adv. Sci. 7 2002203

Li J X, Ávila B E F D, Gao W, Zhang L F and Wang J 2017 Micro/nanorobots for biomedicine: delivery, surgery, sensing, and detoxification Sci. Robot. 2 eaam6431

Hu X H, Yasa I C, Ren Z Y, Goudu S R, Ceylan H, Hu W Q and Sitti M 2021 Magnetic soft micromachines made of linked microactuator networks Sci. Adv. 7 eabe8436

Alapan Y, Yigit B, Beker O, Demirörs A F and Sitti M 2019 Shape-encoded dynamic assembly of mobile micromachines Nat. Mater. 18 1244–51

Alcântara C C J, Landers F C, Kim S, De Marco C, Ahmed D, Nelson B J and Pané S 2020 Mechanically interlocked 3D multi-material micromachines Nat. Commun. 11 5957

Zyla G, Kovalev A, Esen C, Ostendorf A and Gorb S 2022 Two-photon polymerization as a potential manufacturing tool for biomimetic engineering of complex structures found in nature J. Opt. Microsyst. 2 031203

Potyrailo R A, Ghiradella H, Vertiatchikh A, Dovidenko K, Cournoyer J R and Olson E 2007 Morpho butterfly wing scales demonstrate highly selective vapour response Nat. Photon. 1 123–8