Thermal Properties of Soft Nanomaterials Materials Synthesis and

Thermal Properties of Soft Nanomaterials: Materials Synthesis and Fabrication Marconnet Thermal & Energy Conversion Lab Meng Pan, Yu Han GM: Collier Miers, PI: Amy Marconnet

Introduction • Soft nanomaterial: Hydrogel+Nanoparticle – A class of cross-linked polymers – Nanoparticles allow tuning material properties – Gelatinous state and mechanical instability • Objectives: – Engineer a soft nanomaterial – Measure thermal properties See Yu Han’s poster for more details about measurement techniques 2

Challenge of Measuring Soft Materials • How do you measure the temperature without thermocouples? • Hydrogels swell, change shape, and need to be contained during synthesis and measurement Embedded Heater Before 1 hour After 3 IR Thermal Mapping

Determining Temperature Infrared Microscopy: 2 D Temperature mapping with high spatial resolution (1. 7 to 12 µm/pixel depending on magnification) Movie mode allows 10 Hz frame rate time dependent temperatures to be captured 4

Angstrom Method x Thermal Diffusivity: h, To Heat/Cool Modified Angstrom Method: (1) IR camera for 2 D thermal movies Higher accuracy and more data points (2) Square-wave heating source + Fourier Transform to analyze data http: //2. bp. blogspot. com/_ok. Ics. Bie. X 4 U/TRKog. EZh 16 I/AAAAAIY/sp Ys. URz. N 3 d 0/s 1600/squarewave 32 ter ms. png 5 Ghasemi et al. “High Thermal Conductivity Ultra-High Molecular Weight Polyethylene (UHMWPE) Films”, ITHERM 2014, Orlando, FL.

Determining Temperature 6

Materials Synthesis Material Fabrication: Freeze-thaw method Materials fabricated - Poly vinyl alcohol (PVA) - PVA & Poly vinyl pyrrolidone (PVP) - PVA & Dimethyl sulfoxide (DMSO) - Above hydrogels with nanoparticles Temperature 25 C Freeze-thaw method - Soluble materials - Certain hours of freezing and certain hours of thawing as one cycle - More cycles increase porosity -20 C cycle Time Separated Cross-linked http: //kinki. chemistry. or. jp/pre/a-54. html 7

Materials Synthesis: Results PVA plastic PVA+PVP hydrogel PVA+DMSO hydrogel PVA+PVP Gold Nano hydrogel 8

IR Microscope: Results • Thermal Diffusivity: Measurement in progress Othermal properties 9

IR Microscope: Results PVA-PVP Gold Nanoparticle Diffusivity VS Time 3 E-07 Diffusivit(m 2/s) 2 E-07 Algorithm 1 Algorithm 2 1 E-07 5 E-08 0 E+00 30 35 40 45 50 Time (min) 10 55 60 65 70

Conclusion • Developed a method for fabricating hydrogels with and without gold nanoparticle for thermal characterization. • IR results allow measurement of thermal diffusivity with low error (<10%). Need additional measurements of heat capacity and density to get thermal conductivity. – Hydrogel with gold nanoparticles had >15 x larger thermal diffusivity than pure hydrogel. – As hydrogel with gold nanoparticles shrunk, thermal diffusivity increased significantly • Future Work: – New Hydrogels: • PVA based hydrogel with different combination • Poly N-isopropylacrylamide (PNIPAM) based hydrogel – Improved metrology taking into account hydrogel swelling and shrinking. 11

Acknowledgement • Soham Ghosh and others from Prof. Bumsoo Han’s Biotransfer Phenomena Lab. • Summer Undergraduate Research Fellowship • NSF's Nanotechnology Undergraduate Education (NUE) program 12

Thank you 13

Determining Temperature Voltage [V] 3ω Method: Time [s] Use square waves to achieve the power we need. http: //2. bp. blogspot. com/_ok. Ics. Bie. X 4 U/TRKog. EZh 16 I/AAAAAI Y/sp. Ys. URz. N 3 d 0/s 1600/squarewave 32 terms. png Miers, C. & Marconnet, A. D. (2014). “Simulation and Analysis of an Integrated Device to Simultaneously Characterize Thermal and Thermoelectric Properties”. International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES) , West Lafayette, IN, 2014. 14

Modified Angstrom Method Thermal Diffusivity: Phase Lag: Re-Arrange Equation for Fitting: Matlab Plot 1: y = m x Fit Slope Ghasemi et al. “High Thermal Conductivity Ultra-High Molecular Weight Polyethylene (UHMWPE) Films”, ITHERM 2014, Orlando, FL. Matlab Plot 2: Fit Slope y = m x 15

3ω Method: Preliminary Results Stainless Wire SMS Heating Sample 16