BIOMATERIALS and BIO-INSPIRATION:Challenges and Opportunities

Joanna Aizenberg

Harvard University/SEAS-CCB

Challenges

• The existing huge gap between our present use of physical sciences in studying biological matter and an enormous

undeveloped potential of biosystems

• How would we go about mapping engineering and physical

sciences onto biology for technology, medicine, security and

societal needs?

• Scientists began to ask an important question of how to use

biological strategies to make materials that build themselves, repair themselves and evolve

• Can we make our materials multifunctional, dynamically tunable, and responsive?

Challenges

• To understand increasingly complex systems, physicists continue to apply the familiar paradigms: the use of energy minimization, symmetries and conservation laws. However, despite substantial effort, these approaches have largely failedin providing a rational physics-based framework for important biological problems

• We cannot even begin to mimic or grasp the remarkable success of evolution in creating intricate ways to solve the problems of living matter, even if they are not fully optimized;nor can we predict the elegant symmetries and hierarchical, robust structures that form as an embryo develops into a fully grown organism; nor can we extend the great success of equilibrium statistical mechanics to the highly non-equilibrium regime essential to describe biological systems

It is critical to develop new physics concepts that will lead to understanding the underlying design principles,

mechanisms and dynamics in biology

Challenges

• Meeting this challenge requires substantial advances in experiment, simulation and theory

• For experiment, there are grand challenges in monitoring arbitrary single molecules in cells, developing detectors for key biological events at different length scales, and applying developing technologies to collect essential statistics on the huge libraries of molecules or cells required to uncover new physical principles that control biological processes

• For simulation, the important challenge is how to deal with the extensive genomic and structural data, and to reduce this to meaningful and valuable physical principles

• For theory, the overarching challenge is to understand what types of questions can be answered convincingly. Key issues include the role of information science in biology and elucidating mechanisms by which complexity emerges from evolution. In addition, the success of equilibrium statistical mechanics must be extended to address the inherent non-equilibrium nature of biology

Why now?

• Powerful new methods of nanoscale fabrication, characterization, and simulation – using tools that were not

available as little as five years ago – create new opportunities

for understanding, manipulating and mimicking biological materials and processes

• Additional optimism arises from impressive strides in genetics, molecular and cell biology

• The synergistic development and application of approaches that have traditionally been confined to different disciplines are

emerging organically in the scientific community

• The formation of multidisciplinary teams of fundamental

physical, chemical, and biological scientists working together

with engineers

• We begin to re-evaluate existing educational programs and

create new programs at the intersection of fields

WHY BIOMATERIALS and BIOMIMETICS?

• In the course of evolution, nature has developed biomolecularstrategies that endow biological processes with exquisite selectivity and performance.

• The end products of these processes are unique materials and devices fulfilling diverse functions.

• Biology exercises a level of molecular, cellular and system control over the physical and chemical properties of matter thatis unparalleled in today’s technology.

• In the last decade, there has been an explosion of information describing unusual natural structures that are super strong, super adhesive, super hydrophobic, super hydrophilic, super efficient, self-cleaning, self-healing, self-replicating, multifunctional, with superior designs and intricate shapes, etc.

Only the latest realization that the scientific frontiers lie at the intersection between biology, materials science and physics, and the involvement of engineering into the study of nature,

made these unexpected discoveries come to light

WHY BIOMATERIALS and BIOMIMETICS?

Biological systems provide numerous

examples of elaborate materials with

exceptional nanostructural, mechanical,

optical and magnetic properties

Biological systems provide numerous

examples of elaborate materials with

exceptional nanostructural, mechanical,

optical and magnetic properties

Mimicking Nature’s methods of biological

manufacture is proving to be a major step

forward in modern chemistry, materials

science and engineering

Mimicking Nature’s methods of biological

manufacture is proving to be a major step

forward in modern chemistry, materials

science and engineering

1 µm

Physical sciencesPhysical sciences

EngineeringEngineering

OBJECTIVES of BIOLOGICAL and BIOMIMETIC MATERIALS and DEVICES RESEARCH

• Search for biological systems with unique micro- and nano-designs and superior optical and mechanical performance

• Learn about their structure, properties, tunability and mechanisms of formation

• Identify new bio-inspired fabrication and self-assembly strategies to be incorporated into devices

• Integrate novel materials synthesis with nanotechnology to mimic advantageous biological systems

• Apply to novel electronics, photonics, structural materials, sensors, tissue engineering… and MORE!

• Search for biological systems with unique micro- and nano-designs and superior optical and mechanical performance

• Learn about their structure, properties, tunability and mechanisms of formation

• Identify new bio-inspired fabrication and self-assembly strategies to be incorporated into devices

• Integrate novel materials synthesis with nanotechnology to mimic advantageous biological systems

• Apply to novel electronics, photonics, structural materials, sensors, tissue engineering… and MORE!

BiologyBiology

FIBER-OPTICAL NETWORK in a DEEP-SEA GLASS SPONGE

-20 -10 0 10 201.44

1.45

1.46

1.47

1.48

Radial position (µm)

Refr

active

In

de

x

TransverseAxial

Vitreous silica

Core

• A crown of glass fibers remarkablysimilar to commercial optical fibers:

– Raised refractive index core that could carry a single-mode optical signal!

– Most likely it functions as a multimode waveguide

• Protein-reinforced laminar structure provides advantageous mechanical properties

• No birefringence

• Sodium-doped structure

• Light concentration by lensarextension

• Low-temperature synthesis

J. Aizenberg, et al. Nature 424, 899 (2003); Proc. Nat. Acad. Sci. 101, 3358 (2004).

NEARLY-PERFECT MICROLENSES in BRITTLESTARS

• Nearly-perfect lens design:

• Compound-eye function capability

• Inspiration for biomimetics

� Micron-scale

� Aberration-free

� Birefringence-free

� Unique focusing effect and signal enhancement

� Angular selectivity

� Photochromic activity

� Intensity adjustment

� Individually-addressed

� Mechanically strong

J. Aizenberg, G. Hendler, Nature (2001); J. Mater. Chem. (2004)

Opportunities

• The gecko’s foot, lotus leaf, mussel byssus, mollusk shells, bones, spider silk, Venus’s Flower Basket, butterfly wings,

brittlestar optics have fueled a recent escalation of interest to

“smart” biological materials from physical scientists and engineers

• These creatures obviously possess skills and attributes beyond conventional engineering

• If these inspirational biological systems can be reformulated ina synthetic context then perhaps the biomimetic design of

nano- and microscale materials and composites could be a real future possibility

Multidisciplinary research in this exciting area will become a critical theme of the biomolecular and bio-inspired physical

sciences