This document discusses biomimetic materials, which are materials developed through mimicking biological structures found in nature. It provides examples of biomimetic materials like nacre-inspired materials and artificial muscles. Nacre-inspired materials are discussed that mimic the structure of mother-of-pearl to create strong, lightweight composites for bone repair. Different types of artificial muscles are also summarized, including electroactive polymers, shape memory alloys, and shape memory polymers that can contract, expand or change shape in response to electrical, thermal, or chemical stimuli like natural muscles. Biomedical applications of these biomimetic materials are highlighted such as SMPs for tissue engineering and controlling cell morphology.

1. Biomimetic Materials
Tomsk Polytechnic University
Исследовательская школа химических и
биомедицинских
Antonio Di Martino
dimartino@tpu.ru

2. BIOMIMETIC MATERIALS
materials developed by replication or imitation of biological structures
Honeycomb Wood fibers
Nacre
Mother of pearl
Hedgehog quills
 Bio-inspired materials engineering: applying biological principles to synthetize new materials
 Bio-mediated materials engineering: take advantages of biological materials properties by incorporation into another
system
 Biomimicry : new science that studies nature's models and then imitates or takes inspiration from these designs and
processes to solve human problems

3. Biological materials
Typically found as composite structures, can be classified as:
Non-mineralized ( soft) Mineralized (hard)
Proteins ( e.g. collagen, keratin, elastin)
Polysaccharides (e.g. chitin, cellulose, hemicellulose etc)
Soft tissue
 Intramolecular bonds such as H-bond;
 crosslinking of polymer chains
muscles
fat
blood vessels
synovial membranes
Organic + Inorganic crystals ( high strength)
Inorganic components
 Calcium carbonate – CaCO3
 Calcium phosphate – Ca3(PO4)2
 Silicon dioxide – SiO2
 Iron oxide – Fe2O3
Hard tissues are: bonesSoft tissues are

4. Biomimetic materials
 Nature synthetize its materials under mild conditions:
 Ambient temperature
 Ambient pressure
 Near-neutral pH
 The idea behind the biomimetics are:
 Understand the parameters which control biological
self-assembly and mineralization
 Understand both the synthesis-structure and
structure-property relationship of biological materials
 Developing of next-generation high performance
multifunctional materials

5. Advantages of biological systems
Six major characteristics that make biological systems advantageous:
 Self-assembly
 Multi-functionality (same material for different application)
 Hydration
 Evolution
 Synthesis in mild conditions
 Hierarchical structures
Hierarchical structure of bones

6. Nacre-inspired materials
 Bio-materials, such as mammalian bones, crustacean shells and reptile skins have unique properties that are intimately
associated to their structure
 Associated properties are often the result of a combination of two distinct components: a ‘hard’ component, and a
‘soft’ component, consisting of organic matter, such as collagen, elastin or cellulose.
 Nacre consists of 95 wt% of aragonite, which is a crystalline
form of CaCO3 and 5 wt% organic materials, which are proteins
and polysaccharides

7. Nacre-structure
Proteins

8. Nacre inspired materials
 Nacre inspired porous scaffolds for bone repair have been established via a combination of strategies, including
electrospinning, phase separation, and 3D printing
 Polyimide layers = soft part =
 Hard part
Clay (глниа) = SiO2, Al2O3, MgO + organic compounds
TiO2
polyimide
polydimethylsiloxane
 Incorporation of antibacterial compounds on the surface ; e.g. Silver nanoparticles
 Mechanical properties like natural bones
chitosan
hyaluronic acid

9. Biomimetic artificial muscles
Artificial muscles are materials or devices that mimic natural muscles and can reversibly contract, expand, or
rotate within one component due to an external stimulus (such as voltage, current, pressure or temperature)
Artificial muscles are divided in three major groups based on the actuation mechanism
 Electric actuation – Electroactive polymers (EAPs)
 Pneumatic actuation (PAMs)
 Thermal actuation – Shape memory alloy (SMA) – Shape memory polymers (SMPs)
Pneumatic Artificial Muscles

10. Electroactive polymers (EPAs)
EPAs = polymers that exhibit a change in size or shape when stimulated by an electric field
Large deformation when a large force is applied over time
EPAs are divided in two main groups: Dielectric and Ionic
 Dielectric = electrostatic forces between two electrodes squeeze the polymer.
It is required high voltage to produce high electric fields.
 Ionic = the response is related by the displacement of the ions inside the polymers
(e.g conductive polymers)
The cations in the ionic polymer-metal composite
are randomly oriented in the absence of an electric field.
Once a field is applied the cations gather to the side of the
polymer causing the polymer to bend. Applied voltage = polymer expand (blue)
Voltage is removed (red muscles)
the polymer returns to original state.

11. Shape Memory Polymers (SMPs)
Polymers with ability to return from a deformed state (temporary shape) to their original (permanent) shape
induced by an external stimulus (trigger)
heat electric magnetic light chemical

12. Shape memory polymers (SMPs)
 Physical cross-linked polymers
 Chemical cross-linked polymers
 The thermal-induced SMPs as the most researched SMPs, can change their shape in a predefined way under
the stimulus of heat
 Electric-induced SMPs
 Magnetic-induced SMPs
indirect thermal-induced SMPs
electricity or magnetism are
transformed to heating
 Photo-induced SMPs form or destroy the networks in polymers under different wavelength
 Chemical-induced SMPs
water induced
solvent-induced
pH-induced

13. Shape memory polymers (SMPs)
Traditional SMPs – Dual SMPs
Temporary shape
Permanent shape
Triple SMPs 2 Temporary shapes
Permanent shape
Quadruple SMPs
3 Temporary shapes
Permanent shape
Multi-stimuli SMPs
Multi-functional SMPs
polymers can recover shape under more than one stimuli
possess not only shape memory properties but also other stimuli-
responsive function, such as healing, drug delivery

14. Composition of biodegradable/biocompatible shape memory systems

15. Shape memory effect of PDLLA/HA composite at 70 °C
Examples of SMPs
Temperature
Shape memory poly(ε-caprolactone-co-DL-lactide) (PCLA)
Water
It recovers the shape after 30 minutes at body temperature
It takes 36 seconds in hot water to recover the initial shape (in vitro)
The same polymer in vivo used as stent for esophagus
 Soft material
 Adaptable to tissue

16. Examples of SMPs
Water-induced SMPs
 The absorbed water can be divided into
 free water = cannot affect the properties of the SMPs = no changes of shape
 bounded water = affect the shape = weaken the hydrogen bonds in polymer networks
to increase the flexibility of the macromolecular chains
Poly(vinyl alcohol) (PVA)
 nontoxic nature and biocompatible material
 both the chemically and physically crosslinked networks
 good water induced shape memory effect
MCC = microscristalline cellulose
Cellulose

17. pH-induced SMPs
 Body compartments have variations in physiological pH values
 In pathological conditions the pH is some body compartments can be different than in healthy conditions
 pH sensitive groups
 amino
 carboxyl
 sulfonic
 pH induced shape memory effect is achieved through
switching effect of hydrogen bond interactions of pH
sensitive groups in polymer
The pH-sensitive memory effect of polyurethane with pyridine rings
1) The disturbed hydrogen bond
interactions
of pyridine rings cause swelling
in acid condition
2) The formed hydrogen bond
interactions lead to de-swelling
in base condition

18. Light induce SMPs
 Photosensitive functional group
e.g azobenzenes
Interpenetrating polymer network (IPN polymer)
containing cinnamylidene acetic acid terminal group.
100% elongation
Initial state
λ > 300 nm
for 35 min
deformation
λ = 254 nm
for 120 min
recovery
cinnamylidene acetic acid

19. Reversible SMPs
 one-way SMEs materials can remember and recover shape in only one direction
 two-way SMEs
the materials can reversibly change shapes between temporary shape and
permanent shape under different external stimuli (reversible SME)
reversible bidirectional shape memory effect

20. Biomedical Applications
SMPs-based Biomaterials for Tissue Engineering
(a) compressed scaffold
(b) the scaffold implanted in the rabbit mandibular bone defect
(c) and (d) the scaffold cans recovery the original shape in vivo
after 10 min of implantation

21. SMPs-based Substrate to Control Cell Morphology
 rat bone marrow mesenchymal stem cell (rBMSC) shape
 reorganization of actin cytoskeleton, and differentiation by the dynamic change of a
microgrooved surface activated with the thermal-induced shape memory effect
Confocal laser scanning microscopy images

22. SMPs-based Substrate to Control Cell Morphology

23. Shape Memory Alloy (SMA)
 Alloy : combination of metals or a combination of one or more metals with non-metallic elements
 A shape-memory alloy : it is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape
when heated.

24. Shape Memory Alloy
 The two most prevalent shape-memory alloys are:
NiTinol wires (Ni-Ti)
Copper –Aluminium-Nickel ( Cu-Al-Ni)
Nickel- Titanium (NiTi)
 Others SMA : Fe-Mn-Si ; Cu-Zn-Al; Cu-Al-Ni; Au alloy with Fe, Zn, Cu

25. Shape memory effect
 The shape memory effect (SME) occurs because a temperature-induced phase transformation reverses deformation
 Two common effects are one-way and two-way shape memory
Start
Apply a deformation
Heating
Cooling
ONE-WAY DEFORMATION TWO-WAY DEFORMATION
Start
Apply a deformation
Heating T1
Heating T2
Cooling
T1<T2
The material remember
two different shapes at two
different temperatures

26. Biomedical applications
Robotic hands
SMA to move fingers
Liftware spoon
To counteract the tremor associate
with Parkinson s disease
Dental braces

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