sign in sign up
<<
Home , Electrospinning

Electrospinning of Carbon Nanotubes Composites Milind Gandhi1 and Frank Ko2 1-Biomedical Engineering, Sciences and Health System, Drexel University, Philadelphia, PA 19104 2- Fibrous Materials Laboratory, Department of Materials Science and Engineering, Drexel University , Philadelphia, PA 19104 FML

Background Materials and Methods Fiber Morphology and Diameter

Ratios: x 1000 x 5000 x 35000 •Dragline silk from major ampullate glands of spider, Nephila clavipes is a x 1000 x 5000 x 35000 MaSp1 to MaSp2 fibrous protein with unique characteristics of combined strength and elasticity. FML MaSp1 (3:1) It is stronger than steel, as extensible as rubber and has a water uptake 12%- 12%-10cm- comparable to wool. 10cm- 30kV • The silk fiber has crystalline regions of anti-parallel β-sheet interspersed with 30kV elastic amorphous segments similar to liquid crystalline . These two segments are represented by two different proteins, MaSp1 (Major Ampullate (1:1) MaSp2 10%-10cm- Spidroin 1) and MaSp2 (Major Ampullate Spidroin 2) coded by different 12%-10cm- 30kV genes. 30kV •Nexia Biotechnologies Inc., in 1999 introduced an innovative technology of using transgenic approach to produce recombinant spider silk. They produced (1:3) R R 6%-10cm- recombinant spider silk, Biosteel in BELE (Breed Early Lactate Early) goat 30kV system. The milk produced by Nexia’s transgenic goats contains spider silk proteins which can be isolated and purified to homogeneity. They have MaSp1:12%-10cm-30kV MaSp2: 12%-10cm-30kv MaSp1:MaSp2(3:1): 12%-10cm-30kv MaSp1:MaSp2 (1:1): 10%-10cm-30kv MaSp1:MaSp2 (1:3): 6%-10cm-30kv successfully isolated MaSp1 as well as MaSp2. 14 50 14 30 30 12 12 40 •While the biotechnology pathway to large scale manufacturing of spider silk is 10 10 20 20 30 promising, the strength of the recombinant silk is far from satisfactory in spite 8 8 6 20 6 10 4 4 10 of its high level of elongation at break. 10 Std. Dev = 36.43 Std. Dev = 17.48 Std. Dev = 29.73 Std. Dev = 25.75 2

Frequency Frequency 2 Std. Dev = 25.17 Frequency

Mean = 100.7 Mean = 28.7 Frequency Mean = 57.4 Frequency 10.0 30.0 50.0 70.0 90.0 110.0 130.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0Mean = 81.1 10.0 30.0 50.0 70.0 90.0 110.0 130.0 1 200. Mean180.0 = 163.39 1 160.1 180. 90. N = 100.00 1 170.0 0.0 N = 100.00 0 120.01 140. 50. 70. N = 100.00 0 1 6 0 80.09 100.01 30. 0 0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 0 30.0 50.0 70.0 90.0 110.0 130.0N =150.0 100.00 130.0140.0 5 0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 50.06 7 0. 10. 0 0 0 0 110.012 0.0 .0 10.02 30.04 0. 0. 0 0 0 9 100.0 0.0 N = 100.00 0. 0. 0 0 0 0 70. 80.0 0 0 0 5 6 .0 3 40. 0 0.0 0 10.0 2 0 .0 Fiber diameter (nm) Fiber diameter (nm) Fiber diameter(nm) Fiber0 .0diameter(nm).0 0 Fiber diameter(nm) Objective Tensile Properties Chemical Composition •Taking advantage of the super strength of a carbon nanotube (CNT), we hypothesize that the composite consisting of recombinant spider silk and CNT 0.70 MaSp1 provided by Nexia Electrospun aligned Spider silk, MaSp1 (Average from 5 samples) 80000 0.65 Electrospun MaSp1 75000 Electrospun MaSp1with 1% CNT 0.60 will have the mechanical properties comparable or superior to those of natural 45.0000 70000 0.55 65000 0.50 40.0000 60000 spider silk. 0.45 55000 0.40 •We plan to test this hypothesis by fabricating a novel in a 35.0000 50000 45000 0.35

40000 Absorbance 0.30 30.0000 MaSp1 with 1% CNT Count process of co- of spider silk and CNT in electrostatic field. 35000 0.25 30000 25.0000 0.20 25000 On the basis of elongation balance we concluded that the spider silk (20-30% 0.15 20000

20.0000 15000 0.10 elongation at break) and CNT (6-30% elongation at break) are compatible 10000 Electrospun MaSp1 0.05 15.0000 5000 0.00 material systems MaSp1 0 -0.05 10.0000 200 300 400 500 600 700 800 900 10001100120013001400150016001700180019002000 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 Raman Shift

•We intend to combine these tailorable superior mechanical properties with the Average Stress (MPa) Results 5.0000 Wavenumber biocompatible nature of spider silk at a nanoscale level and explore the Raman spectra of electrospun MaSp1 fibers 0.0000 FTIR spectra of MaSp1 0.0000 0.0200 0.0400 0.0600 0.0800 0.1000 0.1200 0.1400 with and without CNT feasibility of the “super silk’ as scaffolds. powder and electrospun fibers •MaSp1 was successfully electrospun at 12 % wt in formic acid at spinning Average Strain distance of 10 cm and voltage of 3 kV/cm. 1% CNT was added to MaSp1 and was spinnable at 10 % at similar distance and electric field. Both aligned as Modulus Maximum Elongation Conclusion Hypothesis well as random fibers were formed. The aligned fibers with and without CNT (MPa) Stress at break (MPa) (%) R were tested by Kawabata microtensile tester . •Individual components of spider silk (Biosteel ) in different MaSp1 123.2982 9.5948 ± 14.33 ± ratios produced by transgenic technology were successfully • Mixing MaSp1 and MaSp2 in different ratios to prepare the spinning dope •MaSp2 was spinnable at 12% but with beads at similar spinning conditions. ± 29.2264 3.7077 3.98 electrospun to obtain nano scale diameter aligned as well as might produce silk with unique and tailor made properties. For •Ratios of MaSp1 to MaSp2 - 3:1 was spinnable at 12 % but for 1:1 and 1:3, MaSp1 + 1004.3658 40.7422 ± 7.3973 ± random fibers. silk-CNT composite preparation, CNTs must be dispersed in the silk viscosity was too high and had to reduce it to 10% and 6% respectively. 1% CNT ± 546.76 18.0545 2.6103 •Incorporation of carbon nanotubes (CNT) in spider silk solution so that individual tubes are well separated from each other, improved the mechanical properties of fibers. approaching the level of mono-dispersion. Spinning parameters used in the experiments… •Preliminary analysis with FTIR proved electrospinning does • The electrostatic charge during electrospinning along with the flow Reservoir containing BiosteelR and CNT not change the chemical composition of spider silk. will help in aligning the CNT in the spider silk polymer matrix therefore •Concentration of spider silk (%wt): 6 - 12 •Raman spectroscopy results proved that CNT are in the resulting in strong and tough fibrils unmatched by any known synthetic •: Formic acid fibers. materials. •Electric field (kV/cm): 1-6 • Nanofibrous structures fabricated by the electrospinning process are •Diameter of spinneret: 18-G needle characterized by ultrahigh surface area to volume ratio with morphology Power supply •Angle of spinneret: 45˚ Future direction similar to natural extracellular matrices, a wide range of pore size Collecting plate •Spinning distance (cm): 5 - 10 distribution, and a high porosity. Cells seeded on the biocompatible silk Further optimization of electrospinning parameters to nanofibrous structure might proliferate and migrate under the guidance of produce continuous uniform fibers. fiber orientation. Acknowledgement Incorporation of CNT having higher concentrations. 1-10 nm CNT in 10-100 nm Spider silk Nanocomposite of Chemical and thermal annealing to improve the mechanical CNT and Spider David Von Rohr, Tim Kelly for their assistance in ESEM, Raman and FT-IR. properties. silk Schematic of electrospinning procedure Nexia Biotechnologies for providing us with transgenic spider silk. This project In vivo cell culture study to investigate biocompatibility of is supported in part by the Pennsylvania Nanotechnology Institute. spider silk scaffolds for tissue engineering applications.