Multiscale and hybrid manufacturing technologies for advanced electronics, environment

For the last decade, numerous chemical synthesis methods have been developed for the fabrication of functional nanomaterials. However, the integration of bottom-up synthesized nanomaterials in devices has been a great challenge with poor controllability, reproducibility, and reliability. Our group has put great efforts to develop various hybrid nanomanufacturing processes by combining the advantages of top-down and bottom-up nanofabrication methods.

Direct and large-scale micro/nano-patterning of functional nanomaterials:We developed direct nanoimprinting lithography where liquid solution of functional nanomaterials can be used as an ink for the nanoimprinting-based direct nanopatterning process [34-37]. Also, transfer printing process was employed for the large area direct formation of micropatterns of nanomaterials [38]. Furthermore, we have developed a low-cost, large scale nanofabrication of silicon nanomesh via nanosphere lithography of polystyrene beads and plasma etching process [15]. These direct micro/nano-patterning methods can realize facile fabrication of electronic devices such as sensors and field effect transistors.

Templated assembly of nanomaterials and synthesis of functional nanostructures: Metal nanoparticles such as platinum (Pt), palladium (Pd) or silver (Ag) can be used as catalysts for functional devices such as sensors, fuel cells, batteries, etc. We have developed liquid-phase method for the templated synthesis and assembly of metal nanoparticles along the nanowires, instead of vacuum deposition (eg. sputtering or evaporation) [39-41]. By controlling the synthesis parameters (concentration, temperature, time, etc.), we can either form metal-metal oxide hybrid nanostructures or metal nanotubes. Furthermore, multi-metallic nanotubes can be easily fabricated by mixing multiple metal precursors [42]. Also, we developed a facile liquid phase synthesis method of metal nanofibers using virus as a one dimensional template [43].

[34] S-H. Ko, I. Park, H. Pan, C.P. Grigoropoulos, A.P. Pisano, C. K. Luscombe, and J. M. J. Frechet, “Direct Nanoimprinting of Metal Nanoparticles for Nanoscale Electronics Fabrication”, Nano Letters 7,1869-1877, Jun 2007
[35] I. Park, S-H. Ko, H.Pan, E-S. Lee, J-H. Jeong, A.P. Pisano, C.P. Grigoropoulos, and J.M.J. Frechet, “Nanoscale Patterning and electronics on flexible substrate by direct nanoimprinting of metallic nanoparticles”, Advanced Materials 20, 489-496, Jan 2008
[36] S-H. Ko, I. Park, H. Pan, N. Misra, M.S. Rogers, A.P. Pisano, and C. P. Grigoropoulos, “ZnO nanowire network transistor fabrication on a polymer substrate by low-temperature, all-inorganic nanoparticles solution process”, Applied Physics Letters 92, 154102, Apr 2008
[37] E-U. Kim, K-J Baeg, D-Y Kim, Y-Y Noh, D-Y. Kim, T. Lee, I. Park*, and G-Y. Jung*, “Templated assembly of metal nanoparticles in nanoimprinted patters for metal nanowire fabrication”, Nanotechnology 20, 355302, Aug 2009
[38] S. Kim, W. S. Lee, J. Lee, and I. Park, “Direct micro/nano metal patterning based on two-step transfer printing of ionic metal nano-ink”, Nanotechnology 23, 285301, Jun 2012
[39] M. Lim, Y. Lee, S-W. Han, and I. Park, “Novel fabrication method of diverse one-dimensional Pt/ZnO hybrid nanostructures and its sensor application”, Nanotechnology 22, 035601, Jan 2011
[40] Y. Lee, M. Lim, I. Park, and S-W. Han, “Facile Synthesis of Noble Metal Nanotubes by Using ZnO Nanowires as Sacrificial Scaffolds and Their Electrocatalytic Properties”, Chemical Communications 47, 6299-6301, Apr 2011
[41] M. Lim, D. Kim, C-O. Park, Y. Lee, S-W. Han, Z. Li, R.S. Williams, and I. Park, “A new route towards ultra-sensitive, flexible chemical sensors: metal nanotubes by wet-chemical synthesis along sacrificial nanowire templates”, ACS Nano 6, 598-608, Dec 2011
[42] B-S. Choi, Y. W. Lee, S. W. Kang, J. W. Hong, J. Kim, I. Park, and S. W. Han, “Multi-Metallic Alloy Nanotubes with Nanoporous Framework”, ACS Nano 6, 5659-5667, May 2012 (* co-corresponding authors)
[43] I. Kim, K. Kang, M.H. Oh, M.Y. Yang, I. Park, and Y.S. Nam, “Virus-templated Self-mineralization of Ligand-free Colloidal Palladium Nanostructures for High Surface Activity and Stability”, Advanced Functional Materials 27,1703262, Nov 2017

Figure 4. Guided self-assembly of functional nanomaterials: (1) direct nanoimprinting of metal nanoparticles for flexible nanoelectronics fabrication (I. Park, et al., Advanced Materials 2008), (2) Templated synthesis of multimetallic nanotubes (I. Park, S-W. Han, et al., ACS Nano 2012), (3) liquid-phase synthesis of metallic nanofiber using virus template (I. Park, Y-S. Nam, et al., Advanced Functional Materials 2017), and (4) large scale nanomesh fabrication using nanosphere lithography of polymer beads (I. Park, et al., Small 2018)

Localized synthesis of nanomaterials by focused energy field (FEF): 1D nanomaterials are very useful components for sensors, energy, nanoelectronics, etc. However, chemically synthesized nanomaterials should be manipulated and assembled by complicated and time-consuming processes for the device integration. We developed a novel process called “focused energy field (FEF) method” where 1D nanomaterials can be locally synthesized and directly integrated by localized hydrothermal reaction in liquid precursor [44-46]. This novel process requires extremely small amount of chemicals and energy, and allows reliable and robust integration of nanomaterials on the electronic devices without complicated alignment or assembly processes. Furthermore, we have applied this method to the development of low-power gas sensor array on MEMS microheating platforms [47].

Fabrication of heterogeneous nanomaterial array and selective surface functionalization:An array of heterogeneous nanomaterials can be very useful in the chemical sensors, especially the gas sensors which requires multiplexed sensing units for higher detection accuracy. We have employed FEF method for the serial and parallel synthesis of multiple 1D nanomaterials in single device chip [48, 49]. Furthermore, their surface could be selectively functionalized with multiple catalytic metal nanoparticles for enhancing the selectivity to target gas analytes [50, 51].

[44] D. Yang, D.H. Kim, S.H. Ko, A.P. Pisano, Z. Li, and I. Park, “Focused energy field (FEF) method for the localized synthesis and direct integration of 1D nanomaterials on microelectronic devices “, Advanced Materials 27, No.7, 1207-1215, Feb 2015, (Front Cover Article)
[45] C. Y. Jin, Z. Li, R. S. Williams, K-C. Lee, and I. Park, “Localized temperature and chemical reaction control in nanoscale space by nanowire array”, Nano Letters 11, No. 11, 4818-4825, Oct 2011
[46] J. Yeo, S. Hong, G. Kim, I. Park, C.P. Grigoropoulos and S.H. Ko, “Laser induced hydrothermal growth of heterogeneous metal-oxide nanowire on flexible substrate by laser absorption layer design”, ACS Nano 9, 6059-6068, Jul 2015
[47] I. Cho, K. Kang, D. Yang, J. Yun, and I. Park, “Localized Liquid-Phase Synthesis of Porous SnO2 Nanotubes on MEMS Platform for Low Power, High Performance Gas Sensors”, ACS Applied Materials & Interfaces 9, 27111-27119, July 2017
[48] D. Yang, K. Kang, D. Kim, Z. Li, and I. Park, “Fabrication of heterogeneous nanomaterial array by programmable heating and chemical supply within microfluidic platform”, (Nature) Scientific Reports 5, 8149, Jan 2015
[49] D. Yang, M. K. Fuadi, K. Kang, D. Kim, Z. Li, and I. Park, “Multiplexed gas sensor based on heterogeneous metal oxide nanomaterial array enabled by localized liquid-phase reaction”, ACS Applied Materials and Interfaces 7, 10152-10161, May 2015
[50] D. Kim, D. Yang, M.A. Lim, Z. Li, C-O. Park, and I. Park, “In-situ integration and surface modification of functional nanomaterials by localized hydrothermal reaction for integrated and high performance chemical sensors”, Sensors and Actuators B: Chemical 226, 579-588, Nov 2015
[51] J. Suh, I. Cho, K. Kang, S. Kweon, M. Lee, H. Yoo, and I. Park, “Fully integrated and portable semiconductor-type multi-gas sensing module for IoT applications”, Sensors and Actuators B: Chemical 265, 660-667, July 2018

Figure 5. Selective synthesis and direct device integration of 1D nanomaterials: (1) localized synthesis of nanowires by focused energy field (FEF) method (I. Park, et al., Advanced Materials 2015), (2) nanoscale heater for localized synthesis of metal oxide nanowires (I. Park, et al., Nano Letters 2011), (3) multiplexed nanomaterial array by microfluidic precursor supply and localized chemical reaction (I. Park, et al., Scientific Reports 2015), and (4) localized synthesis of metal oxide nanowires on suspended MEMS microheating platform for low power gas sensor (I. Park, et al., ACS Applied Materials and Interfaces 2017)