MIMICKING THE COMPOSITE STRUCTURE OF

SPIDER SILK TO PRODUCE A MATERIAL WITH HIGH

TENSILE STRENGTH AND EXTENSIBILITYTracey Atkinson, Patrick Steiner,

Low Rui Hao, and Lim Yao Chong

Spider Dragline Silk Spider web material that makes up the

main “axels” of orb weaver spider webs High tensile strength and very extensible

Structure of Spider Silk Has a composite structure:

20% crystalline regions80% highly elastic substances

Extendible regions connect crystalline regions to produce the amazing properties of spider silk

Applications of Spider Silk

Range from biomedical uses, like ligaments and sutures, to bullet proof vests and parachutes

Spider silk is not used because it is not readily available and there is no method to mass produce it

Project Objective To create a material with both high tensile strength

and elasticity by mimicking the composite structure of spider silk.

Hypothesis By combining the optimal electrospinning method and

optimal ratio of keratin and elastin, we can create a composite mat with high tensile strength and extensibility comparable to that of spider dragline silk.

Keratin and Elastin

Keratin:a material that provides strength in

biomaterials such as nails, bird beaks, horns, etc.

Biodegradable

Has same beta-sheet composition as spider silk

Elastin:

A material that provides elasticity to artery walls, lung tissue, skin, ligaments, etc.

Biodegradable

More elastic than spider silk

ElectrospinningA polymer is dissolved and placed in a syringe

The solution is charged with a high voltage

The high voltage creates an

electric field that causes the

polymer to be spun out in thin

threads to a collector plate

A fibrous mat is formed

Methodology Part 1

AOS: optimize the spinning of keratin and elastin separately

HCI: verify the AOS results after break Part 2

AOS: determine the best method for combining keratin and elastin

HCI: determine the best ratio of elastin to keratin

Part 1

Optimize the conditions for electrospinning keratin and elastin individuallyVoltageSolventsFlow rateDistance to collector plate

The optimal conditions found will be kept constant in Part 2 of the experiment

AOS Will try multiple variations on

electrospinning, while keeping the ratio of elastin to keratin constant, to produce the material with properties most similar to spider silk

Will use a consistent ratio of elastin to keratin yet to be determined

AOS-Variables

Independent variable: Method for combining elastin and keratin

Dependent variable: Tensile strength and extensibility of fibrous

mat.

Control Variables(constants): Ratio of elastin to keratin, concentration of

separate polymer solutions, voltage, flow rate and distance from the collector plate.

AOS Method 1

The syringes will be placed on opposing sides of a rotating collector plate

Has been found to produce homegenous mats of multiple polymers

AOS Method 2

The syringes will be placed on the same side of a stationary collector plate

AOS Method 3 We will attempt to mix the polymers in

one solution, and spin them from the same syringe

Will be attempted if keratin and elastin can be put into the same solution

HCI Will vary the ratio of elastin to keratin,

while keeping method constant, to produce the properties most similar to that of spider silk

Will use AOS Method 2(parallel syringes) for all tests

HCI-Variables

Independent variable: Ratio of volume of Keratin solution to Elastin

solution used during electrospinning.

Dependent variable: Tensile Strength and Extensibility of Fibrous

mat.

Control Variables(constants): Method of electrospinning, concentration of

separate polymer solutions, voltage, flow rate and distance from the collector plate.

AOS: Optimizing Concentration, Flow Rate, Voltage and Solvent for electrospinning Keratin & Elastin

HCI: Duplicating results with a smaller range of independent variables

AOS: Vary Methods of electrospinning

HCI: Vary Ratio of volume of keratin to elastin solution during electrospinning.

Carry out electrospinning with 5 extreme and sparse ratios (Independent Variable).

Measure Tensile strength and Extensibility of results (Data) by sending fibrous mats to NUS.

From data collected, extrapolate the approximate range of optimal ratio. Carry out electrospinning for the approximate range.

Measure Tensile strength and Extensibility of results (Data) by sending fibrous mats to NUS

Optimal Ratio is found.

Most suitable method is found.

Combine both optimal ratio & most suitable method to create a fibrous mat that could mimic spider dragline silk

Timeline

November to January

•Optimize the conditions for electrospinning keratin and elastin

February

to April

•Test the different methods of combining elastin and keratin

April to

June

•Finalize results and send for tensile testing

January to

February

•Verify the optimal conditions for spinning keratin and elastin separately

March to July

•Find the optimal ratio for combining elastin and keratin

July to

August

•Send for tensile testing and finalize results

Combining Results

If results for ratio are found early enough, the optimal method and optimal ratio will be combined in one final test to see if we were successful in mimicking spider silk