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Azobenzene-Based Photomechanical Biomaterials
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REVIEW
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Azobenzene-Based Photomechanical Biomaterials
Jing Sun, Fan Wang,* Hongjie Zhang, and Kai Liu*
Biomaterials with stimuli sensitivity and good mechanical properties are
garnering interest as an important branch of stimuli-responsive materials.
Among them, photomechanical biomaterials are an emerging class of ecofriendly materials for the development of various biomedical devices because they
offer high spatiotemporal control, on-demand response, and noninvasive
manipulation. In particular, azobenzene can be reversibly converted from the
trans to the cis isomer under irradiation by different wavelengths of light. The
significant changes in structural geometry and excellent fatigue resistance of
azobenzene upon isomerization allow its use in the fabrication of materials with
photoresponsive properties, such as bending, twisting, coiling, buckling,
expansion, or even jumping. However, studies on the photomodulated
mechanical performance of azobenzene-based bulk biomaterials have rarely been
reported. This review focuses on the photomechanical effects that occur in
various systems incorporated with azobenzene moieties. Within this framework,
the advantages of azobenzene in different photomechanical materials, including
liquid crystals, bulk films, gels, and bulk fibers, are discussed. In each section, the
light-induced modulation of mechanical properties, including tensile strength,
modulus, and toughness, is highlighted. Finally, a summary and outlook for the
development of azobenzene-based photomechanical materials is presented.
Dr. J. Sun, Prof. H. Zhang, Prof. K. Liu
Department of Chemistry
Tsinghua University
Zhongguancun N Street, 100084 Beijing, China
E-mail: kailiu@tsinghua.edu.cn
Dr. J. Sun
Institute of Organic Chemistry
University of Ulm
Albert-Einstein-Allee 11, 89081 Ulm, Germany
Dr. F. Wang, Prof. H. Zhang, Prof. K. Liu
State Key Laboratory of Rare Earth Resource Utilization
Changchun Institute of Applied Chemistry
Chinese Academy of Sciences
130022 Changchun, China
E-mail: wangfan@ciac.ac.cn
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/anbr.202100020.
© 2021 The Authors. Advanced NanoBiomed Research published by
Wiley-VCH GmbH. This is an open access article under the terms of
the Creative Commons Attribution License, which permits use,
distribution and reproduction in any medium, provided the original
work is properly cited.
DOI: 10.1002/anbr.202100020
Adv. NanoBiomed Res. 2021, 2100020
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1. Introduction
Stimuli-responsive biomaterials are a class
of materials that exhibit smart behavior:
their physicochemical properties respond
to changes in the external environment,
such as light, temperature, ultrasound,
electricity, magnetic field, and pH.[1–11]
These tailorable systems have promising
biomedical applications in the fields of
drug delivery,[12–16] sensors,[17,18] artificial
muscles,[19–24] actuators,[25–28] and tissue
engineering.[29–31] Among these materials,
light-responsive biomaterials are an emerging class of materials promising for biomedical applications.[32] Compared with
other stimuli, light can be applied in an
on-demand and noninvasive manner to
alter the intrinsic properties of the material
with precise control. Light-responsive molecules, or photoswitches, are used for the
fabrication of light-responsive systems
and biomaterials, such as molecular
motors,[33] optical transistors,[34] optical
data storage,[35] and ion channels.[36]
Although there have been extensive investigations into the controllability of their composition and
morphology, light-responsive materials have some fatal
shortcomings, including a small elastic modulus, low energy
density, and a long response time. This further limits their
application in the biomedical field. The development of
photomechanical biomaterials may be a suitable solution to
address these challenges.
Various photoswitchable molecules, such as spiropyrans, diarylethenes, and stilbenes, have been extensively explored in the
field of light-responsive systems as a way of converting light
energy into mechanical motion. Although reversible photoswitching can be readily achieved, highly crowded environments
may hinder the photoisomerization of these molecules, especially spiropyrans, hindering their precise photomanipulation.
In addition, the functionalization of these molecules often
requires tedious synthetic processes which are expensive and
time-consuming. Unlike most other photoswitchable molecules,
azobenzene (azo-) and its derivatives impart materials with special qualities based on the photoisomerization of azobenzene
between the trans and cis states upon irradiation with different
wavelengths of light (Figure 1).[37–39] In particular, azobenzenes
exhibit high photoisomerization efficiency and the two isomers
exhibit significant geometric structural differences, which permit
their use in the development of new smart materials.[40] For
example, liquid-crystal networks (LCNs) functionalized with
azobenzene moieties can directly convert light energy into
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Figure 1. Photoisomerization of azobenzene under different light
irradiation.
motions such as twisting, rotation, and oscillation, making them
a promising material for building actuators.[32] Artificial
muscles,[41–43] shape-memory materials,[44] and systems with
photocontrolled liquid motion[25,45] have also been developed.
The unique properties of azobenzene have also opened up an
attractive route to investigate the reversible photoswitching of
porosity in molecular crystals. By incorporating photoresponsivity azobenzene groups in the structure, a unique metal–organic
framework (MOF) (UiO-68-Azo) platform was developed for oncommand drug delivery applications.[46] Azobenzene can also be
used to develop new biomaterials that exhibit an on-demand
response to light. This approach will open the door for the construction of desirable DNA nanomolecules and nanodevices.[47]
While photomechanical motion has been widely studied,
reports on the manipulation of the mechanical properties by light
are rare. The ability to tune the mechanical performance of materials on demand using light is advantageous for the development
of photomechanical biomaterials. The highly precise control that
can be achieved in a noninvasive manner renders azobenzenebased photomechanical biomaterials useful in drug delivery,
artificial muscles, and soft tissue engineering.[48] Herein, we
summarize the recent advances in the fabrication of azobenzene-based biomaterials and focus specifically on the modulation
of the mechanical performance of the as-obtained material under
special wavelength irradiation. We highlight the fabrication of
azobenzene-based liquid crystals (LCs), bulk films, gels, and
protein fibers. In each section, the modulation of the mechanical
properties of the azobenzene-based materials is discussed.
Finally, we provide a conclusion and outlook for future
applications of azobenzene-based materials.
2. Azo-Based LCs
The photoisomerization of azobenzene can be translated into
macroscopic motion because of the significant geometrical
change involved. Thus, the incorporation of an azobenzene moiety into a LC network allows the manipulation of the alignment
of LC domains using light. However, the mechanical behavior of
such azo-based LCs has rarely been investigated.
To explore the photoresponsive mechanical properties of LCs,
Hermann and coworkers developed a new class of nematic DNA
thermotropic liquid crystals (TLCs) through the electrostatic
complexation of DNA and a cationic azobenzene-based surfactant (Figure 2).[49] Polarized optical microscopy (POM) demonstrated that the dsDNA–Azo complex has birefringence with
typical schlieren textures under ambient conditions, indicating
the formation of a nematic TLC phase. A combination of
time-dependent POM analysis and differential scanning calorimetry (DSC) measurements demonstrated that the nematic
Figure 2. Schematic illustration and photomodulating mechanical properties of the dsDNA–Azo nematic LCs. A) By using electrostatic complexation
between double-stranded DNA and Azo-based surfactant, the dsDNA–Azo nematic LC materials were obtained. A typical schlieren texture of nematic
mesophase was confirmed by POM analysis. The scale bar is 100 μm. In addition, two broad diffraction peaks from small-angle X-ray scattering (SAXS)
measurement demonstrate the trans ! cis isomerization in nematic dsDNA–Azo TLC by light. B) Atomic force microscopy (AFM)-based nanoindentation
of the dsDNA–Azo complex. The top is the surface topography of the TLC material before and after UV light irradiation. The middle is the F–D curves of
the TLC material under different conditions. The bottom is the histogram of the calculated spring constant for the TLC material. Reproduced with
permission.[49] Copyright 2017, Wiley-VCH.
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mesophase of the dsDNA–Azo complex changed completely to a
transparent isotropic liquid above 110 C. Furthermore, smallangle X-ray scattering analysis demonstrated that the behavior
of the dsDNA–Azo complex before and after UV irradiation
was different (Figure 2A). Notably, the trans ! cis isomerization
of the azobenzene moiety was successfully achieved in the solvent-free DNA TLC, thereby decreasing the stiffness of the TLC
material after UV irradiation (Figure 2B). These behaviors demonstrate that azobenzene can be used to manipulate the structural and mechanical properties of azo-based LCs, which
opens the door for the development of DNA-based smart
materials.
3. Azo-Based Bulk Films
In addition to azo-based LCs, azo-based bulk films have received
tremendous attention in past decades. In 2009, Hammond and
coworkers reported azo-containing siloxane-based liquid-crystalline polymer (LCP) films that exhibited reversible mechanical
properties and conformational changes upon UV light irradiation (Figure 3).[50] In detail, poly(vinyl-methylsiloxane) (PVMS)
was functionalized with an azobenzene moiety via platinumcatalyzed hydrosilylation. It was found that the viscoelastic properties were dependent on the morphology of the LCP. When all
azo moieties were in the trans conformation, the well-ordered
smectic layers of the smectic mesophase provided additional
interchain interactions that reinforced the LCP, resulting in a
higher shear modulus. Notably, irradiation with UV light led
to a decrease in the storage and loss moduli of the LCP. This
can be ascribed to the disruption of the smectic mesophase
induced by trans ! cis photoisomerization, which disrupts the
additional interchain interactions.
Although considerable efforts have been devoted to investigating the photomechanical properties of azo-based biomaterials,
the relationship between the structure and mechanical properties
of these materials is not yet well understood. To address this
issue, the optical and mechanical properties of azobenzene-containing LC films were measured simultaneously (Figure 4).[51] To
avoid interference due to the high absorbance of the azobenzene
moiety, the concentration of azobenzene in the LC films was
fixed at 5 mol%. In this study, upon UV irradiation (365 nm,
10 mW cm2, 5 min), the LC films exhibited typical macroscopic
bending behavior due to trans ! cis photoisomerization. The
photogenerated stress also influenced the birefringence of the
LC film. In addition, it was found for the first time that the
Young’s modulus of the LC films decreased significantly after
UV light irradiation.
Recently, Sorelli and coworkers investigated the mechanical
properties of Disperse Red 1 (DR1)-azobenzene-functionalized
PMMA thin films. They found that the mechanical properties
of the thin films changed significantly with light illumination.[52]
During statistical loading/unloading tests, DR1 molecules
underwent isomerization and a photostationary equilibrium
was formed between the trans and cis isomers, resulting in a
decrease in the hardness and irreversible viscosity of the film
under illumination. Notably, the hardness and viscosity of the
thin films could be restored when the light was turned off.
The most drastic variation was that the indentation creep coefficient increased significantly under illumination. This behavior is
related to the reinforcement of the viscoplastic property of the
film after trans ! cis photoisomerization. Furthermore, a thorough study was conducted on the effect of azobenzene loading
on the mechanical properties of azo-based thin films under light
irradiation. A series of photoresponsive copolymers of methyl
methacrylate (MMA) and methacryloyloxy azobenzene
(MOAB) (P(MMA/MOAB)) with different loadings of azobenzene (10%, 15%, 20%, 30%, 45%, 65%, and 80%) were prepared
by casting at room temperature.[53,54] Nanoindentation analysis
demonstrated that the stiffness of the P(MMA/MOAB) films
upon UV light irradiation increased up to 19% with an optimum
loading of 30% azobenzene. The original stiffness can be
restored by irradiating the thin films with visible light, attributed
to the cis ! trans photoisomerization of azobenzene. In addition,
UV irradiation of the indented region of the thin film revealed
healing properties, indicating the potential for the application of
such copolymers in the field of self-healing materials.
In addition to materials with covalently attached azobenzene
molecules, an electrostatic layer-by-layer deposition technique
has been used to fabricate supramolecular materials. In 2007,
Figure 3. A) The schematic illustration of azobenzene-based LCP. The trans ! cis photoisomerization of LCP results in the change from smectic to
isotropic LC mesophase. B) Dynamic rheological properties of LCP under/without UV irradiation. Adapted with permission.[50] Copyright 2009, WileyVCH.
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Figure 4. A) The chemical structures of azobenzene used to generate LC films. B) Schematic illustration of a typical setup for the photoinduced structural
and mechanical properties of the LC films. C) Typical stress–strain curves for LC film samples before/after UV light irradiation (5 min, 365 nm,
10 mW cm2). It was found that Young’s modulus of such films was decreased owing to the photoisomerization from trans ! cis after UV light irradiation.
Adapted with permission.[51] Copyright 2011, American Chemical Society.
Stumpe et al. developed azobenzene-containing materials based
on electrostatic interactions between photochromic azobenzene
moieties and polyelectrolytes.[55] In this study, owing to the orientation of azobenzene, the as-obtained material underwent a
reversible induction of optical anisotropy by exposure to linearly
polarized light at 488 nm, which returned to induced anisotropy
relaxation after the switch-off of the actinic light.
4. Azo-Based Gels
Polymer gels have attracted special attention for their possible
biomedical applications, such as self-healing, soft tissue engineering, drug delivery, and wound healing. However, the weak
mechanical strength of these gels significantly hinders their performance. The effective and reversible photoisomerization of
azobenzene allows the regulation of the gel mechanics and
the overall network. Unfortunately, the cis isomer can isomerize
to the trans isomer thermally over time, which affects the modulus of azo-based gels to some degree. To tackle these challenges, a
long half-life for the cis isomer is the key to controlling the gel
mechanics of azobenzene. Anseth and coworkers incorporated
azobenzene into peptide cross-linkers in polyethylene glycol
(PEG) hydrogels to develop a 3D hydrogel platform for the reversible control of matrix elasticity in cells with photoresponsive
mechanical properties (Figure 5).[56] The hydrogen bonds with
the surrounding network were disrupted under UV irradiation,
resulting in decreased matrix elasticity. Elasticity was fully
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recovered under visible light irradiation or thermal relaxation.
Therefore, such PEG-based hydrogels can be stiffened or softened reversibly upon photoisomerization of azobenzene. The
shear modulus of the PEG-based hydrogels decreased to
100–200 Pa (shear storage modulus, G 0 ) upon UV light
(365 nm) irradiation, and the gel’s initial modulus was recovered
after irradiation with visible light. This behavior can be used to
elucidate the behavior of adherent cells affected by dynamic
matrix stiffness. Valvular interstitial cells (VICs) were encapsulated
in photoresponsive gels. The cell-laden gels demonstrated high cell
viability after treatment with UV irradiation (10 mW cm2,
5 min) and visible light irradiation (10 mW cm2, 2 min).
In terms of their high water content, traditional stimuliresponsive hydrogels are quite biocompatible; however, their
poor mechanical properties limit their practical applications.
Li et al. successfully solved this dilemma by preparing a lightand reductant-responsive polyurethane azo–cyclodextrin (CD)
hydrogel with good mechanical properties (Figure 6).[57] The
polyurethane hydrogel was prepared via the reaction between
hydroxyl and isocyanate groups. AFM and rheometry were conducted to investigate the stiffness and viscoelastic properties of
the gels. Upon approach, the hydrogel (water content:
91.2 0.4%) exhibited a tensile modulus and storage modulus
of 36.5 0.5 and 52.9 1.2 kPa, respectively. After treatment
with UV irradiation, the isomerization of the azo moiety caused
the expulsion of the hydrophobic group from the CD cavity, thus
increasing the tensile strength and decreasing the viscosity of the
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Figure 5. Schematic illustration for the fabrication of photoresponsive hydrogels. It was shown that the photomechanical behavior can be achieved upon
different wavelength light irradiation. Reproduced with permission.[56] Copyright 2011, American Chemical Society.
Figure 6. Schematic for the construction and mechanical performance of dual-responsive polyurethane hydrogel. A) Synthetic routes toward the synthesis of hydrogels. B) Possible structures of the polyurethane hydrogel after UV irradiation and reductant treatment. It was found that the azobenzene
moiety dislocated from the CD cavity after UV irradiation, leading to the aggregation of the cross-linker. C) The typical stress–strain curves for polyurethane hydrogel under different conditions. Adapted with permission.[57] Copyright 2015, Royal Society of Chemistry.
material. Moreover, this highly elastic hydrogel was able to
stretch and warp with a high water content. Owing to their photoresponsiveness and good mechanical properties, such hydrogels
can be used to load/release drugs upon UV irradiation.
Ion gels exhibit solid-like mechanical properties while maintaining the intrinsic properties of ionic liquids (ILs). Watanabe
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et al. developed a unique material, an ABA triblock copolymer
ion gel in a photoswitchable azobenzene IL (Figure 7).[58] In their
study, PBnMA-b-PMMA-b-PBnMA (BMB) and PPhETMA-bPMMA-b-PPhEtMA (PMP) were synthesized via atom transfer
radical polymerization to explore the viscoelastic behavior by
photoisomerization (Figure 7A). It was found that the two ion
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Figure 7. The fabrication and mechanical performance of ABA triblock copolymer gels. A) The structures of ABA triblock copolymer ion gels.
B) Photoswitchable gelation behaviors of ABA triblock copolymer ion gels under cyclic switching of different wavelength of light irradiation.
Reproduced with permission.[58] Copyright, 2019, Royal Society of Chemistry.
gels exhibited opposite viscoelastic behaviors upon irradiation
with light of different wavelengths. In the BMB ion gel system,
a sharp decrease in G 0 was observed after UV light irradiation.
More importantly, the BMB ion gels remained in their gel state
even under prolonged UV exposure for 8 h, indicating a stable
soft gel state (Figure 7B, left). In stark contrast, the PMP ion gels
underwent a gel-to-sol transition upon visible-light irradiation
(Figure 7B, right). The changes in the viscoelastic value of the
PMP ion gel were less significant than those in the BMB ion
gel. The results indicated that ion gels with different viscoelastic
behaviors can be achieved by combining different triblock
copolymers and Azo-ILs.
5. Azo-Based Protein Fibers
Protein-based fibers are suitable for practical applications
because of their excellent mechanical performance, light weight,
good biocompatibility, and biodegradability.[59–65] Stimuliresponsive fibers have received tremendous attention over the
past decade.[66] For example, azobenzene-functionalized crosslinked liquid-crystalline fibers are capable of macroscopic
movements stimulated by UV light irradiation.[67] Unlike photoinduced mechanical motion, the manipulation of fiber
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mechanics by light is rarely reported and remains a considerable
challenge.
Recently, our group reported the design and construction of
bioengineered protein-based fibers with light-induced reversible
mechanical performance in the bulk state (Figure 8).[68] By
exploiting electrostatic complexation between supercharged polypeptides (SUPs) and negatively charged azobenzene-based surfactants (Azo), SUP–Azo fibers can be easily obtained from the
SUP–Azo coacervate. The as-spun protein fibers exhibited excellent mechanical properties. More notably, this is the first report
of the modulation of the mechanical behavior of as-spun fibers by
light. Both tensile test results (Figure 8B) and AFM measurements (Figure 8C) demonstrated that the mechanical performance of the SUP–Azo fiber improved due to the trans ! cis
isomerization in the solid-state by light. Based on nuclear magnetic resonance (NMR) spectroscopy calculations, it was found
that the cation–π interactions in the SUP–Azo fiber play a vital
role in improving the mechanics of the fiber (Figure 8D). During
trans ! cis photoisomerization, the geometrical structure of the
azobenzene moiety changed significantly, which shorten the distance between the phenyl rings of the azobenzene and the unoccupied cationic lysine residues. This resulted in strengthened
cation–π interactions, as in the cis state, both phenyl rings can
interact with the protonated ϵ-amino group of lysine. The
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Figure 8. Schematic representation for the fabrication and mechanical properties of SUP–Azo fiber. A) The SUP–Azo fibers were produced via electrostatic interaction between the SUP and azo-based surfactant. B) The determination of mechanical performance for SUP–Azo fiber by tensile testing,
including Young’s modulus, toughness, strength, and extensibility. C) AFM measurement for SUP–Azo fiber under different conditions (before UV
irradiation, after UV exposure, and dark adaptation). D) A possible mechanism for the SUP–Azo fiber with photoresponsive mechanical properties.
Adapted with permission.[68] Copyright 2020, Wiley-VCH.
mechanical behavior of the SUP–Azo fiber was restored after
dark adaptation because of the decrease in the relevant
cation–π interactions. These results demonstrate that the
mechanics of the SUP–Azo fibers can be regulated reversibly
by light. This behavior paves the way for the development of
smart protein-based mechanical materials.
6. Summary and Outlook
Owing to the high spatiotemporal control, eco-friendliness,
instantaneity, and noninvasive manipulation offered by using
light as a stimulus, light-responsive biomaterials have been
widely investigated for the development of various devices for
biomedical applications. Azobenzene, a unique and powerful
photoswitchable molecule, exhibits excellent reversible photoisomerization efficiency accompanied by significant changes in
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geometry. This behavior can be exploited to develop next-generation photomechanical materials whose optical, electronic, chemical, and mechanical properties can be manipulated. Owing to
the advantages of simple synthetic methods, high conversion
efficiency, and reversible photoisomerization, azobenzene-based
biomaterials exhibit promise for application in actuators, artificial muscles, optical data storage devices, tissue engineering,
and drug delivery. Therefore, we summarize in this review
the recent advances in the modulation of mechanical properties
and applications of azobenzene-based light-responsive biomaterials. We have classified these materials into different systems,
such as LCs, bulk films, gels, and protein fibers. The reversible
photomodulated mechanical performance of such azo-based biomaterials has been highlighted.
Exploiting photoinduced molecular rearrangements permits
the alteration of the mechanical properties of a material upon
light irradiation. Toward this end, azobenzene-based
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biomaterials offer great opportunities for various biomedical
applications. Notably, in situ mechanical manipulations could
be precisely controlled by incorporating an azobenzene moiety
into the architecture. Moreover, azobenzene-based photomechanical biomaterials offer a noninvasive approach and show
promise for applications in artificial muscles and soft tissue
engineering.
Although various azo-based biomaterials have been developed,
several challenges still need to be addressed to take full advantage
of this simple molecule, especially in the biomedical field. As
light is a clean and powerful energy source, the creation of materials whose mechanical behavior can be manipulated on demand
by light is highly desirable. The wavelength of irradiation and
conversion efficiency must be carefully matched to the desired
applications. At present, the biocompatibility and biodegradability of azo-based biomaterials are their main limitations in biomedical applications. The wavelength required to trigger
photoisomerization in these materials is another drawback
because typical UV-range irradiation is undesirable in biomedical applications. Thus, the azobenzene moiety requires structural
modifications to alter the isomerization wavelength to make it
compatible with biological applications. The fatigue resistance
of azo-based biomaterials also requires improvement. Further
investigations may achieve such improvement by methods such
as new design strategies and the integration of multistimuliresponsive systems. Overall, the development of azobenzenebased light-responsive biomaterials with various tailored
properties will open up new possibilities for the development
of next-generation smart biomaterials.
Acknowledgements
This work was supported by the National Key R&D Program of
China (grant nos. 2020YFA0908900, 2020YFA0712102 and
2018YFA0902600), K. C. Wong Education Foundation (grant no. GJTD2018-09), the Natural Science Foundation of China (grant nos.
21877104, 21834007, 21907088, and 22020102003), the Youth
Innovation Promotion Association of CAS (grant no. 2020228), and
Young Elite Scientists Sponsorship Program by CAST (grant no.
2018QNRC001).
Conflict of Interest
The authors declare no conflict of interest.
Keywords
azobenzene, biomaterials, mechanical performance, photomodulating,
photoresponsive
Received: January 28, 2021
Revised: April 15, 2021
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Jing Sun received his B.S. degree in Chemistry from Southwest University (China) and his M.S. degree in
Organic Chemistry from Nankai University (China) in 2011 and 2014, respectively. He obtained his Ph.D.
degree from the University of Groningen, The Netherlands, under the supervision of Professor Andreas
Herrmann in 2020, working on engineered protein-based biomaterials. Since August 2019, he is a
postdoctoral researcher at the University of Ulm, Germany. Currently, his research focuses on dissipative
self-assembly.
Fan Wang did her bachelor’s study at Lanzhou University in 2012 and then she received her Ph.D.
degree in Inorganic Chemistry from the University of Chinese Academy of Sciences, China, in 2017. From
2017 to 2019, she worked as a research assistant professor at Changchun Institute of Applied Chemistry.
In 2020, she was promoted as a research associate professor and now she is focusing on synthesis and
biomedical applications of bioinorganic composite materials.
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Kai Liu received his Ph.D. degree from the University of Groningen, The Netherlands, in 2015. Then he
pursued postdoctoral studies at the University of Groningen, The Netherlands and Harvard University,
USA, respectively. In 2017, he was appointed as a principal investigator at Changchun Institute of
Applied Chemistry of Chinese Academy of Sciences and focused on engineered biomaterials and hightech applications. In 2020, he moved to the Department of Chemistry of Tsinghua University, Beijing,
and promoted as a tenured professor, and heads a laboratory performing research on the interface of
biotechnology, biosynthetic materials, and information technology.
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