RESEARCH PROGRAM OF CHRISTINE ORTIZ

Multiscale Approach:single molecules →biomimetic assemblies → matrix of single cells → in-tact tissue

Musculoskeletal (internal to the body)(e.g. cartilage, bone, etc.)

Exoskeletal (external to the body)(e.g. gastropod molluscs, armored fish, etc.)

Engineering motivation:

-Bio-inspiration and guidance for improved materials for

protective and structural

applications

Medical motivation:-to facilitate the

development of improved clinical treatments for

disease & injury through tissue repair and/or

replacement→ regenerative medicine /

tissue engineering

-nanoscale forces and displacements (F, ), constitutive laws ()-local, spatially-specific material properties (E, Y, H, energy dissipation, etc.)

-molecular-level structure-property relationships-novel mechanical phenomena (e.g. nanogranular friction, fracture localization, etc.)

Objective :A Fundamental, Mechanistic-Based Understanding of

Tissue Function, Quality, and Pathology

NANOMECHANICS OF STRUCTURAL BIOLOGICAL MATERIALS

SELECTED RECENT ACCOMPLISHMENTS

(MUSCULOSKELETAL)

● Prior to tenure: established the use ofnanomechanics in near-physiological conditionsapplied to healthy musculoskeletal tissues

● Post-tenure: application of nanomechanics to thefield of tissue engineering; temporal evolution of thequasistatic mechanical properties (Ng+ J. Biomech.2007) and dynamic visco(poro)elasticity (Lee+J. Biomech. 2009) of the tissue engineered cartilagematrix associated with individual cells

● Assessment of engineered tissue quality and

heterogeneity locally at unprecedented resolutions as a function of cell type, scaffold, growth factors, etc.

● Relevance to mechanotransduction

COLLABORATORS● A.J. Grodzinsky (MIT-BE), D. Gazit (Hebrew U.)

RESEARCH PROGRAM OF CHRISTINE ORTIZ NANOMECHANICS OF STRUCTURAL BIOLOGICAL MATERIALS

viscoelasticity + poroelasticity

(Buschmann+)

10 µm

2

p v

L

Hk

chondrocyte, stem cell

AFM colloidal tipmatrix

RESEARCH PROGRAM OF CHRISTINE ORTIZ NANOMECHANICS OF STRUCTURAL BIOLOGICAL MATERIALS

0

90

180

270

360

450

0 35 70 105 140Penetration Depth (nm)

Fo

rce

(µ

N)

BerkovichExperimentalφ = 15º, c = 100 MPa

FEA=15º, c =100 MPa

Mineralized Collagen Fibril

Mineral Particles

Cohesive Bonding

Frictional Contact

Mineralized Collagen Fibril

Mineral Particles

Cohesive Bonding

Frictional Contact

SELECTED RECENT ACCOMPLISHMENTS

(MUSCULOSKELETAL)

● Prior to tenure: established the experimental and theoretical methods for high resolution imaging and nanomechanics of bone

● Post-tenure Postulated a new theory for the strength on bone involving "nanogranular friction" (Tai+ Nano Lett., 2006, featured in Nat. Nanotech. News and Views, 2006, commentary; J. Am. Acad. Ortho. Surg. 2007); discovered a new energy dissipation mechanism in mineralized biological tissues; nanoscale heterogeneity (Tai+ Nat. Mater. 2007)→assessed nanoscale properties of stem cell-based tissue engineered bone (Tai+ J. Biomech., Pelled+ Tiss. Eng. 2008).

● Understanding the mechanisms that prevent our

bones from fracturing under physiological loading will aid in the treatment of problems that result from old age, disease, and injury.

COLLABORATORS● F. Ulm (MIT-CEE), S. Suresh (MIT-DMSE), D.

Gazit (Hebrew U.)

RESEARCH PROGRAM OF CHRISTINE ORTIZ NANOMECHANICS OF STRUCTURAL BIOLOGICAL MATERIALS

penetration ontop of fish scale

Ganoine

Dentin

Isopedine

Bone 10 μm

cross section of fish scale

SELECTED RECENT ACCOMPLISHMENTS

(EXOSKELETAL)

● Prior to tenure: established an experimental and theoretical framework for studies of mineralized biological materials at the nanoscale, using nacre as a model system

● Post-tenure Determined multilayered design (i.e. thickness, sequence, and material properties of individual layers) of a natural armor which facilitate circumferential fracture and prevent interfacial delamination under a penetrating load (bite from predator) in order to localize impact and prevent catastrophic failure (Bruet+ Nat. Mater. Cover 2008, Wang+ JMR 2009, Yao+ PNAS, 2009)

● Bio-inspiration and guidance for improved

materials for protective and structural applications (Ortiz & Boyce Science 2008)

COLLABORATORS● M.C. Boyce (MIT – MechE), D. Gazit (Hebrew

U.)

SELECTED RECENT ACCOMPLISHMENTS(EXOSKELETAL)

● Defense Science Study Group (DSSG) 2008-2009● Department of Defense National Security Science and Engineering

Faculty Fellows: NSSEFF (468 white papers resulted in 17 semifinalists being invited to submit full proposals and in person interviews → 10 awardees selected)→ $4.6M total

● MIT Institute for Soldier Nanotechnologies (Grantee, 2002-present)● Raytheon, Inc.

RESEARCH PROGRAM OF CHRISTINE ORTIZ NANOMECHANICS OF STRUCTURAL BIOLOGICAL MATERIALS

l1

l2

l3

l4

()1(CTE)1

durable functionally graded interphases − mitigates delamination

multilayered design (layer thickness, sequence) − penetration resistance, minimizes back-deformation into soft tissue, prevents catastrophic fracture (self-healing),

thermal management, weight reduction

interlocking articulation at reinforced joints

anisotropic constitutive models of individual layers − local stress

distributions

curved geometry (shape / size) of individual armor units – energy absorption, ergonomics

Rt

li

tissue finite viscoelastic deformation

(damage tolerance)

1

2

3

,E H

z z

, , , = ,

, , , ,1 2 3, 13 23, 12 12 32 31

Y,1 Y,2 Y,3 Y,3 Y,13 Y,23 Y,12

E = E E G = G G

z

anisotropic spatial arrangement of armor

units – cooperative deformation of entire

body

biomechanical flexibility

MOBILITY PROTECTION

()tgeometry and mechanical

properties of threat (e.g. penetrating indenter)

Ru

()2(CTE)2

()3(CTE)3

()4(CTE)4

unique organic-inorganic nanocomposite morphologies (e.g. fibrous, prismatic, nacreous etc.) - energy

dissipation

camouflage pigmentation

back deflection

4 Sub-Programsa) Flexible natural armorb) Transparent natural armorc) Natural armor for blastd) Natural armor for extremeenvironments (deep sea)