Slide 1 : Hydrogels for Artificial Muscles
Major Project Presentation Supervised by,
Dr. Sureyya Saricilar
Prof. Geoffrey Spinks Submitted by,
Karthika Prasad
3372194
AIM : AIM Attempt to make double network hydrogels fit enough to work as actuators for artificial muscles.
Introduction : Introduction Hydrogels - water swollen three dimensional networks of polymer chains. Quite similar to biological systems. Interesting stimuli response
Wide applications in biological system
Why double network hydrogel ? : Why double network hydrogel ? Compression of Single Network hydrogel Compression of Double Network Hydrogel
EXPERIMENTAL : EXPERIMENTAL Materials used
2-acrylamido-2-methyl propanesulfonic acid (PAMPS)
Potassium persulphate(KPS),
N,N methylene bis acryl amide, (NMBA)
Acrylic acid, (AAc)
2-hyroxy-2-methylpipus phenone
Triethylene glycol dimethacrylate Swelling and Mechanical properties of 1.5mm thick
PAMPS-AAc DN hydrogel studied The pH response of various thickness of hydrogels studied
Slide 6 : DN hydrogel
1st network was immersed in the 2nd network solution
Kept under UV for 6 hours to let polymerization take place. Preparation of Hydrogels DN hydrogel was synthesized by polyemerization technique 1st Network
Desired concentrations of PAMS, KPS and NMBA mixed
Was kept oven at 60 C for 24 hours. 2nd Network
AAc, 2-hyroxy-2-methylpipus phenone and Triethylene glycol dimethacrylate were mixed at desired concentrations
Experimental : Experimental 1.5mm 0.5mm 0.16mm Materials of various thickness were used to prepare gels
Swelling experiment : Swelling experiment PAMPS/AAc hydrogels samples were cut into circles and were socked in buffer solutions with pH values varying from 2.14 to 7.96.
Increase in the weight of hydrogel were noted in each case.
Mechanical Tests : Mechanical Tests Compression
Compression tests were carried out using a mechanical tester ( Instron ).
Circular shaped gel samples swollen in buffer solution of varying pH (2.14, 2.91.3.72.4.72,5.72.6.91.7.96) were used.
Mechanical tests : Mechanical tests Tensile test
The samples were cut into dumbbell shape.
Procedure similar as compression test using the INSTRON testing machine.
Samples were then placed into different buffer solutions of pH varying from pH 2.2 to pH 7.96.
Actuation test : Actuation test The pH sensitivity of the DN hydrogels was tested by performing actuation test
Gels were cut into rectangular pieces and were soaked in pH 2.14 and pH 7.96 to reach equilibrium
Gels of 3 different thicknesses that’s 1.5mm, 0.5mm and 0.16mm were used to do the actuation test.
Results and Discussion : Results and Discussion General comments
Transparent
Tough
Contains more than 90% water
Sample gels soaked in pH 4.72 and pH 5.72 were opaque
Swelling experiments : Swelling experiments The samples were dried after equilibrium swelling have been attained
Equilibrium water content = [(Ws – Wd)/Wd]* 100
Ws and Wd are the weights of swollen and the dry hydrogel respectively
Fig:1 Swelling behavior of DN hydrogel at different pH
Swelling experiment : Swelling experiment Samples showed a tremendous increase in their weights for the first 4 hours
Gels from pH 2.14 to pH 3.72 and from pH 5.72 to pH 7.96 are in swollen state
Gel at pH 4.72 was in shrunken state and was opaque due to the salt effect between the COO- ion in the 2nd network and K+ ion present in the electrolyte
Mechanical tests : Mechanical tests Compression
Graphical representation of Compressive behavior of
hydrogels at different pH
Fig 2:Compressive stress-strain behavior at pH 2.14 to 7.96
Compression contd… : Compression contd… Compressive stress varied from 0.3MPa to 3.3Mpa with 99% strain at all the cases
The modules varied from 30KPa to 340KPa
Modules was calculated by dividing stress with strain
Gels were strong at pH less than 4 due to hydrogen bonding
Tensile test : Tensile test Fig :3 Tensile stress-strain behavior at pH2.14 to pH 7.96
Tensile test cond.. : Tensile test cond.. Fracture strain of 1120% at lower pH (pH 2.14) and around 120% at higher pH (pH 6.91)
Fracture strength varied from 0.09MPa (pH 6. 91) to 0.5Mpa (pH 2.14).
First linear part of the tensile curve gave the Young’s Modulus of each sample
Modulus varied from 165KPa (pH 6.91) to 346 KPa(pH 2.14)
Actuation test : Actuation test Gels of varying thickness were used
Cyclic transaction between pH 4.72 and pH 7.96
Fig 4 Cyclic transaction between pH 4.72 and pH 7.96 of 1.5mm thick gel
Maroon color – pH 4.72 to pH 7.96
Blue color – pH 7.96 to pH 4.72
Actuation test : Actuation test Fig: 5 Cyclic actuation of 0.5mm thick gel
Actuation test : Actuation test Fig: 6 Cyclic actuation of 0.16mm thick gel
Actuation test : Actuation test The 1.5 mm thick wire took more time for expansion and contraction when compared to the other two.
The transactions took place due to the effect of pH on the gel and due to the applied stress.
Diffusion took place along the axis where force was applied.
Conclusion : Conclusion Actuation behavior of the gel was studied with the help of testing swellability and mechanical properties of gel.
The strength of the hydrogel was not as high as anticipated.
As the thickness of the gel decreases, the quicker response towards pH will be showed by the gel.
Acknowledgement : Acknowledgement Dr. Sureyya Saricilar,-whose encouragement, guidance and support from the initial to the final level enabled me to develop an understanding of the subject.
Prof. Geoff Spinks, who made available his support in a number of ways.
I am indebted to Dr. Philip Whitten and Gina Gilbert who trained me to use the mechanical tester at IPRI.
Slide 25 : Any
Questions ?????