Impact of cellulose fiber organization and novel fiber assembly techniques

Center for NanoCellulosics

Impact of cellulose fiber organization and novel fiber

assembly techniquesJeffrey M. Catchmark

Department of Engineering Science and MechanicsDepartment of Agricultural and Biological Engineering

School of Forest ResourcesVivek Verma

Department of Engineering Science and MechanicsNicole R. Brown

School of Forest ResourcesWilliam O. Hancock

Bioengineering

International Conference on Nanotechnology for the Forest Products Industry

June 13-15, 2007


Overview

Background and motivation for studying cellulose assembly.

Impact of mechanical percolation on cellulose nanofiber composite materials.

Finite element modeling of idealized cellulose nanofiber architectures.

Cellulose nanofiber assembly approach using a system of biomolecular motors and microtubule templates.

Summary


J.F.V. Vincent, U.G.K. Wegst / Arthropod Structure & Development 33 (2004) 187–199

Cellulose: One of nature’s best materials


Cellulose nanofiber bundles

6 Assembly proteins (rosette) which produces cellulose nanofibersCandace Haigler and Larry Blanton, Cellulose: You're surrounded by it, but did you know it was there?

jupiter.phys.ttu.edu/corner/1999/dec99.pdf www.ita.doc.gov/td/forestprod/

~28nm

Wood is an exceptional organized nanocomposite

• Wood has exceptional mechanical properties not only because of the high modulus of cellulose but also due to the way cellulose is organized with hemicelluloses and lignin in the cell wall.


Many hard biological tissues, such as tooth (a), vertebral bone (b), or shells (c) are made of nanocomposites with hard mineral platelets in a soft (protein) matrix. (From : Huajian Gao, et. al., PNAS, May 13, 2003, vol. 100, no. 10, 5597–5600.)

Examples of other natural nanocomposites

J.F.V. Vincent, U.G.K. Wegst / Arthropod Structure & Development 33 (2004) 187–199.


J.F.V. Vincent, U.G.K. Wegst / Arthropod Structure & Development 33 (2004) 187–199.

Scanning electron microscope image of the structure of cuttlefish bone. [Taken from: S. Kannan a, J.H.G. Rocha b, S. Agathopoulos c, J.M.F. Ferreira, “Fluorine-substituted hydroxyapatite scaffolds hydrothermally grown from aragonitic cuttlefish bones”Acta Biomaterialia 3 (2007) 243–249.]

Examples of other natural nanocomposites


Lignocellulose is a major materials industry Wood, wood fiber composites and paper represent a $250 billion

dollar per year industry. Reduction in the use of fiber could have a major impact. Consider one grand challenge: Reduce fiber content and

thus weight of paper by 50% without impacting its mechanical properties:

Save ~2 billion trees. Reduce water and chemical consumption by ~50%.

– Save ~250 billion gallons of water per year Save >1.2 quads of energy in U.S.(~8% of all energy used in

manufacturing in the U.S., and ~1.2% of the total energy used).

Motivation for studying cellulose assembly


Substantial improvements in the mechanical properties of fiber materials (ex: elastic and shear modulus) are achieved when mechanical percolation is reached in fiber composites.

Non-percolated system Percolated system

Percolation: The formation of connected particles or fibers which span the length of the material.

Mechanical percolation


Plant cell wall Paper

Examples of mechanically percolated materials

Enamel, bone, nacre

Cuttlefish bone


(V. Favier, et. al., Polymer Engineering and Science, Vol. 37, No. 10, 1997).

• Cellulose nanofiber dimensions: 10-20nm diameter - 0.5-5 microns length

• Ecellulose = 150GPa

• Ematrix = 0.5MPa

• Fiber distribution: random.

Finite element mechanical analysis of composites containing nanodimensional

cellulose fiber


Log plot of the measured and calculated shear modulus a function of cellulose fiber volume around the percolation threshold (from V. Favier, et. al., Polymer Engineering and Science, Vol. 37, No. 10, 1997).

Impact of percolation on modulus

Percolation threshold


Log plot of the measured and calculated shear modulus a function of cellulose fiber volume around the percolation threshold (from V. Favier, et. al., Polymer Engineering and Science, Vol. 37, No. 10, 1997).

No control over the relationship between fiber organization and percolation threshold

Impact of percolation on modulus


Engineer fiber organization in cellulose fiber composites to achieve mechanical percolation at lower fiber volumes.

• Produce mechanically similar or improved cellulosic materials using less fiber.

Strategy for improved cellulosic materials


Organized with particles

Random fiber network

All composites contain 144 cellulose nanowhiskers measuring ~2.8 microns by 80 nanometers. Cellulose connections are assumed to be rigid. Cellulose volume – 14.7%All composites assume E=150GPa for the cellulose and E=0.5MPa for the matrix (after previous studied by Favier, et. al.)

Organized composite design assumes E=23GPa for the clay microparticels and E=1GPa for the organic linkers.

Model space measures 14.8m14.8m.

Finite element modeling of cellulose fiber materials

Eeff = 2,790 MPaEeff = 35 MPa

Random with particles

Eeff = 37 MPaEeff = 5,460 MPa

Organized fiber network


Impact of particle and linker on material modulus

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0.01 0.1 1 10 100

E linker or particle

Eef

f of c

ompo

site

mat

eria

l

Eparticle constant

Elinker constant

Linker modulus very important to final modulus of material

Clay (Kaolinite, 23GPa)

Cellulose (150GPa)

Organic linker (1GPa) 25nm coating on clay particle


Eeff = 7,630 MPa

Contour plot of displacement




Eeff = 5,460 MPa



Eeff = 7,630 MPa





Eeff = 5,460 MPa


Fiber organization resulting in mechanical percolation at lower fiber volumes has the potential for improving the mechanical properties of cellulosic materials.


Synthesis approach

System of biomolcular motors and microtubule templates:

Diverse network geometries possible. 2D surface geometry which can be modeled using finite

element analysis.


Biomotors Transport intercellular cargo

on microtubules. Chemically powered locally by

hydrolysis of adenosine triphosphate (ATP).

Microtubules Cylindrical polymers which

form dynamically inside cells to enable transport.

Biomotors ‘walk’ uni-directionally on microtubules.

System overcomes random Brownian motion at this scale. Cooper, 2nd ed.

Centrosome

Newt lung cell

System of biomolecular motors and microtubule templates


Biomotors and microtubules are proteins. Many families of biomotor proteins including the kinesin, dynein and myosin.

Microtubules polymerize inside cells via the ordered assembly of and -tub

ulin proteins, which are linked with GTP (guanosine tri-phosphate). Kinesin biomotor head domains connect to the tubulin subunits.

8 nm

25 nm

Kozielski et al.Nogales et al.Cooper, 2nd ed.

7 nm

Plus end

System of biomolecular motors and microtubule templates


Microtubules and biomotors: the ‘nanoarchitects’ of the plant cell wall

Microtubule formation controls the orientation of cellulose fibrils in the plant cell wall. Cellulose producing enzyme rosettes glide between membrane bound microtubules creating aligned fibrils.

Image by Prof. Malcom Brown,

http://www.botany.utexas.edu/facstaff/facpages/mbrown/newstat/stat38.htm

Alexander R. Paredez, Christopher R.

Somerville, David W. Ehrhardt, Science, Vol.

312, 1491, 2006.


In-vitro use of biomotors and microtubules

Glass Substrate

Casein

Microtubule

Kinesin Cargo

Direction of motion

+ End- End

Glass Substrate

+ End- End

Glass Substrate


Self-organizing microtubules: 2D templates for cellulose nanofiber assembly

F. J. Ne´de´lec, T. Surrey, A. C. Maggs & S. Leibler, NATURE, VOL 389, 18, pp. 305-308, 1997

Aster formation at different motor assembly concentrations: a) 25g/ml, b) 37.5g/ml, c) 50 g/ml and d) 15 g/ml.

Multi-head motor assembly containing 4 kinesin linking 2 microtubules.


Streptavidin binds to 4 Biotin

Building motor complexes

Biotinylate motor end group

Image taken from: http://www.arrayit.com/Products/ Substrates/SuperStreptavidin/superstreptavidin.html


Polymerization of Microtubule Asters

• Polymerization of asters to form microtubule templates with varying degrees of percolation.• Microtubule Aster seeds were formed in solution then immobilized on glass surface• Immobilized microtubule asters were polymerized using tubulin under physiological conditions• During polymerization asters grow in length and get interconnected

t = 10 min t = 40 min t = 130 min


Degree of interconnectivity in microtubule templates

• The connectivity of microtubule asters was measured as a function of time.

• The percent connectivity was calculated as the number of asters connected to at least one other aster divided by the total number of asters observed.

• All asters are interconnected forming a fully percolated network at ~130 minutes of microtubule polymerization time.

0

20

40

60

80

100

0 20 40 60 80 100 120 140

Time (min)

Per

cent in

terc

onnec

tivi

ty (%

)


Linking biomotors to nanofibers

We have implemented a biotinylation scheme as a means of linking biomotors to cellulose nanofibers.

Biotinylated fibers can be linked to biotinylated kinesin biomotors via a neutravidin protein.

Once a fiber assembly is formed, the microtubules can be depolymerized to remove the template, if desired.

Cellulose nanofiber

Biotin

Streptavidin

Biotinylated microtubule

Biotin

Interconnected astersBiotinylation performed using NHS-dPEG™12 Biotin (Quanta Biodesign)


Control experiment

Confirming that biotinylated microtubules bind only to cellulose

Biotinylated cellulose immobilized on glass followed by neutravidin and biotinylated microtubules: Microtubules bound on surface

Control 1: No cellulose lead to no microtubule binding on surface

Control 2: Neutravidin absence leads to no microtubule binding to cellulose

Microtubule on cellulose Control 1: No cellulose Control 2: No neutravidin


Assembly of cellulose nanowhiskers over immobilized biotinylated microtubules.

Biotinylated microtubules were immobilized on APTES coated glass. Biotinylated cellulose was bound to the microtubules via biotin-

neutravidin link

Rhodamine labeled microtubules viewed under Rhodamine emission filter (588nm)

Alexa fluor labeled cellulose viewed under Alexa fluor emission filter (647nm)

Linking cellulose to microtubules

Scale bar 20m


Continue with microtubule aster templates and percolated fiber networks formed using functional clay microparticles.

Linking cellulose to microtubules

Finite element model

Interconnected asters

Alexa fluor labeled cellulose viewed under Alexa fluor emission filter


Potential implications for cellulose based materials

Paper:Eeff = 4-15

GPaCellulose fiber volume: ~66%

Organized nanocellulose (theoretical):

Eeff (compressive) = 7.6 GPa

Fiber volume – 14.7%


Other approaches: “Bucky Paper”

Carbon Nanotube “Bucky

paper”

Image taken from Carbon Nanotechnologies Incorporated at http://www.cnanotech.com/pages/resources_and_news/gallery/3-

2_buckytube_gallery.html


Other approaches: “Bucky Paper”

Carbon Nanotube “Bucky

paper”

A little cost prohibitive: >$1,000/sheet


Real need for improved cellulosic materials which incorporate less fiber while maintaining same or superior physical properties.

Organization of cellulose fiber may provide a path toward substantial improvements in the mechanical properties of cellulosic materials and/or substantial reductions in the amount of fiber consumed.

We have demonstrated the ability to produce organized microtubule templates with controllable degrees of mechanical percolation.

We have attached cellulose to the microtubules using a biotin-streptavidin linker.

We are working toward making cellulose composites using these templates and testing their mechanical properties.

Summary


Acknowledgements

Collaborators:– Prof. Nicole Brown, School of

Forest Resources

– Prof. William Hancock, Bioengineering

Student:– Vivek Verma, Ph.D. Student,

Engineering Science and Mechanics


National Science Foundation Materials Research Science and Engineering Center (NSF MRSEC) Center for Nanoscale Science.


Ben Franklin Technology Partners of Central and Northern Pennsylvania

Acknowledgements


Thank you!

Documents

Impact of cellulose fiber organization and novel fiber assembly techniques