DOI 10.1007/s13233-019-7158-5 www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673 Macromolecular Research Communication Macromol. Res., 27(8), 739-742 (2019) 739 © The Polymer Society of Korea and Springer 2019 Fabrication of Randomly Stooped Polymer Nanohairs Using Scattered Electron Flood under Ambient Condition Abstract: Despite attractive applications of randomly oriented nanostructures with high aspect ratio, their fabrication suffers from both complicated processes and lack of materials. In this letter, we present a simple but effective method for the fabrica- tion of randomly stooped polymeric nanohairs having high aspect ratio under ambi- ent condition by using scattered electron flood. High aspect ratio vertical nanohairs prepared by nano-molding process exhibited randomly stooped geometry after the electron irradiation. Fourier transform infrared spectroscopy and Monte Carlo sim- ulation revealed that radiolysis of polymeric nanohairs by scattered electrons in ambient air allowed directionally random distribution of shrinkage of the nano- hairs, resulting in randomly stooped nanohair structures. Keywords: polymer, nanohairs, electron beam, scattered electron, nanolithography, polymer shrinkage. Nanostructured surfaces (NSSs) with high aspect ratio (AR) inspired by nature are widely studied due to their numerous attractive applications, 1 such as dry adhesion, 2 memory devices, 3 bactericidal activity, 4 superhydrophobicity, 5 field emitters, 6 and antireflective surfaces, 7 etc. These unique properties facilitate such diverse applications are attributed to their diverse geom- etries and configuration. For instance, their shapes, including thickness and AR, modify effective moduli depending on the geometries. They can also enhance tackiness, the shear adhe- sion force between substrate and nanoscale structures. 2 Of the various architectures, it has been reported that ran- domly oriented or aperiodic nanopillars effectively suppress the reflection by either light scattering or tuning the refractive index, which is practically applicable to the field of camouflage and optoelectronic devices used in the military. 8,9 So far, most of these randomly oriented nanopillars are based on inorganic materials such as silicon, and thus suffer from vulnerability to high mechanical modulus and also from their brittleness. Fur- thermore, the fabrication includes high-cost and complicated processes such as high-density electron cyclotron resonance plasma etching. These demerits have limited their potential appli- cations to the preparation of high-throughput and flexible opti- cal films and devices. To circumvent these problems, organic materials possessing sufficient softness, such as polymers, have been employed for the fabrication of functional nanostructures based on the nano- replication process. However, fabrication of stooped polymeric nanohairs exhibited limited scope for the realization of high AR patterns with controlled geometries because replicated struc- tures easily collapsed or paired by capillary force and van der Waals force. 10 Moreover, high-throughput fabrication is also lim- ited because of the high-vacuum condition that is required for the irradiation of electron-beam (e-beam) for stooping nanohairs. This is the reason that, in spite of the optically functional appli- cations, there are only a few published reports on the manufacture of high aspect ratio polymeric nanostructures with randomly stooped geometry. In this letter, we report a simple yet effective method for the preparation of randomly stooped polymeric nanohair structures, which utilizes flood electron beam under ambient pressure. This method features compatibility with high-throughput and large- area fabrication because it does not require any demanding condi- tions such as high vacuum. Severely scattered electrons trajected into the ambient air facilitate random stooping of prepared nanohair structures due to random volume shrinkage by radi- olysis reactions. We also investigated the degree of stooping by controlling irradiation time. Fourier-transform infrared (FT-IR) spectroscopy measurements and Monte Carlo simulations of electron trajectory were performed to analyze the radiolysis reaction and the distributed incident angle of scattered electrons into the nanohairs, respectively. Figure 1 describes the fabrication process for unidirection- ally and randomly stooped nanohairs by e-beam irradiation after replica-molding. A silicon master mold containing hexag- onal nanohole arrays was fabricated by reactive ion etching (RIE) preceded by photolithography. The nanoholes have 100 nm Woojin Jung †,1 Gyeong G. Jeon †,2 Jong Uk Kim 1 Tae-il Kim* ,1 Jong H. Kim* ,2 School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon 16419, Korea 2 Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea Received February 11, 2019 / Revised April 18, 2019 / Accepted April 27, 2019 Acknowledgments: This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP: Ministry of Science, ICT and Future Planning) (NRF-2016M2B2A4912549). This research was also supported by the Basic Science Research Program (NRF-2017R1D1A1B03033089) through the NRF funded by the MSIP. *Corresponding Authors: Tae-il Kim (taeilkim@skku.edu), Jong H. Kim (jonghkim@ajou.ac.kr) Woojin Jung and Gyeong G. Jeon equally contributed to this work.