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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
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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
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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.)
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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.)
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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)