The Woodruff School

SUMMARY

Flexible electronics are attractive for new applications because of their flexible forms as well as properties of light weight and portability. The circuits are usually printed on flexible substrates such as plastic, fabric, and paper, which are delicate and heat sensitive. Traditional photolithography with the use of high temperature and corrosive chemicals is not suitable for flexible substrates. The fabrication of flexible electronics requires fast and low-temperature printing processes in order to minimize the damage of the flexible substrates. In this dissertation, a high-throughput nanoparticle laser patterning (NLP) process for flexible electronics is developed, where nanoparticles are sintered with low power laser while they are selectively deposited to enhance printing quality. Copper and silver particles are successfully deposited on paper and polyethylene terephthalate (PET) substrates. To study the process-structure-property relationship, the effects of process parameters on the performance are assessed. The thermal effect of laser on the morphology and porosity of films are observed under scanning electron microscope. Chemical composition of printed pattern is also characterized using X-ray diffractometer. The sensitivity of electromechanical property with respect to the porosities, as a result of different laser power densities, is analyzed. In theoretical studies, a multiscale model of deposition mechanism is developed, where an analytical adhesion model predicts the deposition performance based on laser irradiation, particle size, temperature, elastic-plastic properties of particle and substrate, and deposition velocity. The mechanical properties of nanoparticles are predicted by molecular dynamics simulation to construct the structure-property linkage at nanoscale. A controlled kinetic Monte Carlo simulation model is applied to build process-structure relationship to predict the morphologies of the printing results at mesoscale. The developed process is demonstrated and applied to fabricate hydrophobic and hydrophilic patterns with controlled oxidation levels on PET substrate, and flexible sensors on paper substrate. Bluejeans Meeting Meeting ID: 103 175 944 https://bluejeans.com/103175944

SUBJECT:	Ph.D. Dissertation Defense

BY:	Ji-Hyeon Song

TIME:	Thursday, December 13, 2018, 6:30 p.m.

PLACE:	MARC Building, 201

TITLE:	A Nanoparticle Laser Patterning Process to Fabricate Flexible Electronics

COMMITTEE:	Yan Wang, Co-Chair (ME, GT) Sung-Hoon Ahn, Co-Chair (MAE, SNU) Shreyes Melkote (ME, GT) Suresh Sitaraman (ME, GT) Seung Hwan Ko (MAE, SNU) Doo-Man Chun (ME, Ulsan Univ.)

SUMMARY Flexible electronics are attractive for new applications because of their flexible forms as well as properties of light weight and portability. The circuits are usually printed on flexible substrates such as plastic, fabric, and paper, which are delicate and heat sensitive. Traditional photolithography with the use of high temperature and corrosive chemicals is not suitable for flexible substrates. The fabrication of flexible electronics requires fast and low-temperature printing processes in order to minimize the damage of the flexible substrates. In this dissertation, a high-throughput nanoparticle laser patterning (NLP) process for flexible electronics is developed, where nanoparticles are sintered with low power laser while they are selectively deposited to enhance printing quality. Copper and silver particles are successfully deposited on paper and polyethylene terephthalate (PET) substrates. To study the process-structure-property relationship, the effects of process parameters on the performance are assessed. The thermal effect of laser on the morphology and porosity of films are observed under scanning electron microscope. Chemical composition of printed pattern is also characterized using X-ray diffractometer. The sensitivity of electromechanical property with respect to the porosities, as a result of different laser power densities, is analyzed. In theoretical studies, a multiscale model of deposition mechanism is developed, where an analytical adhesion model predicts the deposition performance based on laser irradiation, particle size, temperature, elastic-plastic properties of particle and substrate, and deposition velocity. The mechanical properties of nanoparticles are predicted by molecular dynamics simulation to construct the structure-property linkage at nanoscale. A controlled kinetic Monte Carlo simulation model is applied to build process-structure relationship to predict the morphologies of the printing results at mesoscale. The developed process is demonstrated and applied to fabricate hydrophobic and hydrophilic patterns with controlled oxidation levels on PET substrate, and flexible sensors on paper substrate. Bluejeans Meeting Meeting ID: 103 175 944 https://bluejeans.com/103175944