Assembly of Nanoparticles in Multiscales and Multidimensions (Multiscale Architecturng): Platform for Convergence Technology Mansoo Choi Global Frontier Center for Multiscale Energy Systems School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Korea Email : mchoi@snu.ac.kr Seoul National University Global Frontier Center for Multiscale Energy Systems
Why Multiscale ? Example: Solar and Fuel Cells • Energy conversion and transfer in solar and fuel cells are multiscale phenomena • Energy carriers: photon, electron, exciton, plasmon, molecule ion, phonon Multiscale approach integrating nano, micro and macroscales is needed to optimize the process. Seoul National University Global Frontier Center for Multiscale Energy Systems
Plasmonic solar cell utilizes multiscale metal nanoparticle patterns to enable physically thin but optically thick cells to maximize light trapping Optical path length enhancement Multiscale plasmonic solar cells Cui et al., Nano Letters, 2010 Polman and Atwater, Optical Society of path length enhancement America, 2010 Atwater et al., Nature Materials (2010) Seoul National University Global Frontier Center for Multiscale Energy Systems
Surface Enhanced Raman Scattering (SERS) based on nanoparticle patterns Mu et al. (2010), Nanotechnology. , 21: 015604 Seoul National University Global Frontier Center for Multiscale Energy Systems
Nanoparticles: Building Blocks for Nanotechnology l Nanoparticles have long been conceived as the fundamental building blocks for realizing nanotechnology Multiscale Architecturing Nanoparticles It remains challenging for a controlled way of nanoparticle assembly in Nanotechnology multiscales and three dimensions. Seoul National University Global Frontier Center for Multiscale Energy Systems
Some of Existing Nanoscale Patterning Methods Seoul National University Global Frontier Center for Multiscale Energy Systems
Koh et al., Nano Letters, 2011 Liu et al., Nature Materials, 2007 Seoul National University Global Frontier Center for Multiscale Energy Systems
Micro-contact Printing (parallel but , uniform contact problem, difficulty in 3D architecturing) : Whitesides group Wilbur et al., Nanotechnology , 1996 Seoul National University Global Frontier Center for Multiscale Energy Systems
Capillary Force A ssembly Cui et al., Nano Lett., Vol. 4, No. 6, 2004 Seoul National University Global Frontier Center for Multiscale Energy Systems
From traditional gravure printing to high- resolution particle printing KRAUS et al. , Nature Nanotechnology, 2, 570 (2007) Seoul National University Global Frontier Center for Multiscale Energy Systems
Particle structures printed on flat Si substrates. KRAUS et al. , Nature Nanotechnology, 2, 570 (2007) Seoul National University Global Frontier Center for Multiscale Energy Systems
Need to develop Cost-effective High-throughput Nano- Assembly Technique: Multiscale, multidimensional assembly, Parallel, Atmospheric, Nanoscale resolution, Large surface area, Independent of substrates and materials Seoul National University Global Frontier Center for Multiscale Energy Systems
Our Method : Ion Assisted Aerosol Lithography( IAAL) (Nature Nanotechnology(2006), Patents Registered in Korea and USA) l Charged aerosol nanoparticles are precisely positioned on the desired location via ion- induced focusing electrostatic field. l This is a parallel atmospheric process ensuring nanoscale resolution on large surface area. Seoul National University Global Frontier Center for Multiscale Energy Systems
Aerosol positioning and assembling of nanoparticles • As particle size decreases, thermal driven random Brownian motion of nanoparticles becomes significant. 2 k Tt < > = = 2 x B 2 Dt f k : Boltzmann _ constant , T : Temperatur e , B f : friction _ coefficien t t : time , D : Diffusion _ coefficien t of particle Seoul National University Global Frontier Center for Multiscale Energy Systems
Aerosol Positioning and assembling of nanoparticles Brownian random movement (cm 2 /sec) Particle size D at 20 ° C in 1 second 2.77 ´ -7 10 1μm 7μm ´ -6 6 . 75 10 100nm 37μm ´ -4 5 . 24 10 10nm 320μm 5.14 ´ -2 10 1nm 3200μm (= 3.2mm) • Precise positioning of nanoparticles is required for nanoscale assembly of nanoparticles. Suppression of thermal motion of nanoparticles is necessary. Electrostatic force is utilized to suppress random Brownian particle deposition . Seoul National University Global Frontier Center for Multiscale Energy Systems
Ion Assisted Aerosol Lithography Ion( ) and Charged Aerosol ( ) Nanoparticle Injection Charge Accumulation on Surface of PR Si - 4 kV Equi-Potential Line acting as a nanoscopic electrostatic lens Focused Deposition Si - 4 kV PR Strip Seoul National University Global Frontier Center for Multiscale Energy Systems
Through DMA, we select 10 nm silver nanoparticles. 75nm 75nm 230nm 1 m m 1 m m Seoul National University 17 Global Frontier Center for Multiscale Energy Systems
Nanoscopic electrostatic lenses ▶w/ ion injection (4lpm) ▶without ion injection Ion mobility vs particle mobility 135nm 135nm 200nm 200nm Seoul National University 18 Global Frontier Center for Multiscale Energy Systems
Focusing effect with the increase of ion flow rates (Nature Nanotechnology,1, 117, 2006) 0lpm 3lpm 100nm 100nm 100nm 4lpm 6lpm 75nm 35nm 100nm 100nm Seoul National University Global Frontier Center for Multiscale Energy Systems
Simulation of Electrodynamic Focusing of Charged Aerosols ● Particle Trajectories : Langevin Equation d v p = + + + m F F F F p D B E W dt F : Fluid Drag Force D F : Brownian random Force B F : Electric Force E F : Van der Waals Force W ● Electric Field : COMSOL CODE Seoul National University Global Frontier Center for Multiscale Energy Systems
Simulation Results (Journal of Aerosol Science, Nov., 2007) A. No ion injection B. With ion injection, N 2 3lpm C. With ion injection, N 2 6lpm Seoul National University Global Frontier Center for Multiscale Energy Systems
Patterning of nanoparticles that were already made Electrospray of nanoparticle suspension (Applied Physics Letters, 94, 053104, 2009) Seoul National University Global Frontier Center for Multiscale Energy Systems
30nm Polystyrene nanoparticles (a) (b1) (b) 5m m 5m m 5m m Ion shower 30min, V s =- Deposition 30min, 4kV Without neutralizer Seoul National University 23 Global Frontier Center for Multiscale Energy Systems
Results – Charge Distribution Geometric mean : 3.2 With neutralizer GSD : 1.88 Without neutralizer Geometric mean : 134 GSD : 1.49 Seoul National University 24 Global Frontier Center for Multiscale Energy Systems
Inertial effect of 10 nm particles: Too high charge, too high velocity (b) (a) <3um line pattern> Ion shower 30min, Ion shower 30min, Deposition 30min, Deposition 30min, W/O neutralizer W/ neutralizer V s =-4kV V s =-4kV Seoul National University 25 Global Frontier Center for Multiscale Energy Systems
Results – Effects of neutralizer 2 (a2) (b2) 5m m 5m m <2um circle pattern> Ion shower 30min, Ion shower 30min, Deposition 30min, Deposition 30min, W/O neutralizer W/ neutralizer V s =-4kV V s =-4kV Seoul National University 26 Global Frontier Center for Multiscale Energy Systems
Protein Patterning(Human IgG)( Small, 7, 1790, (2011) ) <scale bar = 10 m m> Seoul National University Global Frontier Center for Multiscale Energy Systems
Protein Patterning – nanoscale, parallel method (Small, 2011) <scale bar = 1 m m> Seoul National University Global Frontier Center for Multiscale Energy Systems
Protein Patterning in microfluidic channels Seoul National University Global Frontier Center for Multiscale Energy Systems
Do we need resist prepatterning ? Can we eliminate this process ? Solution : Nanoparticle Focusing Mask ( Small ,Vol. 6, p 2146, 2010 ) Seoul National University Global Frontier Center for Multiscale Energy Systems
Nanoparticle Focusing Mask Seoul National University Global Frontier Center for Multiscale Energy Systems
Nanoparticle Focusing Mask : Silicon Nitride Mask 4 m m aperture mask N 2 ion flow rate of 2 l/min (C) (D) 400 nm 600 nm Gaussian Profile AFM image 4 m m à 0.4 ~ 0.6 m m 4kV, 2lpm Seoul National University Global Frontier Center for Multiscale Energy Systems
Size Control by Ion Flow Rate (Small ,Vol. 6, p 2146, 2010) (A) 0.5 lpm 1000 nm (B) 1 lpm 500 nm (C) 2 lpm 300 nm 4 m m à 0.15 ~ 1 m m (D) 4 lpm 150 nm 4 m m Silicon nitride mask Seoul National University Global Frontier Center for Multiscale Energy Systems
Sequential Deposition Control the space between patterns by sequential deposition Substrate Substrate Schematic of stencil translation Seoul National University Global Frontier Center for Multiscale Energy Systems
Focusing Nano-Mask Focusing Mask with 500 nm line openings (manufactured by e-beam lithography) 500 nm 80 nm Seoul National University Global Frontier Center for Multiscale Energy Systems
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