FABRICATION OF MICRO LINE GROOVES STRUCTURE ON PLASTIC FILM BY COMBINATION OF ULTRA PRECISION MACHINING AND HOT EMBOSSING METHOD

HỘI NGHỊ KHCN TỒN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM FABRICATION OF MICRO LINE GROOVES STRUCTURE ON PLASTIC FILM BY COMBINATION OF ULTRA-PRECISION MACHINING AND HOT EMBOSSING METHOD Duc Phuc Truong1, Masahiko Yoshino2 School of Mechanical Engineering, Hanoi University of Science and Technology No Dai Co Viet Road, Hanoi, Vietnam Tel & Fax: +84 3869-2440 Email: phuc.truongduc@hust.edu.vn Department of Mechanical and Control Engineering, Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan ABSTRACT: In this research, the authors report an efficient method to fabricate micro line grooves structure on a plastic film by combincation of ultra-precision machining and hot embossing method This process is comprised of two steps: machining of micro line grooves structure on a Ni-P plate (called Ni-P master mold); using the Ni-P master mold to imprint the micro line grooves structure to a plastic film by hot embossing The results show that the micro line grooves structure of about µm in pitch and 0.35 µm in height was sucessfully fabricated on the plastic film with high fidelity, low cost and high throughput The Ni-P master mold can be used many times to imprint micro line grooves structure on plastic films This demonstrates a possibility for fabrication of high precision micro line grooves structure without using costly methods like photolithography Keywords: micro lines structure, ultra-precision machining, master mold, plastic film INTRODUCTION Metallic nano/micro structures have reported a broad applications such as in electronic devices [1-2], bio sensors [3-6], photovoltaic devices [7-8], display devices [9], and catalyst [10-11] These applications generally utilize the special properties of metallic nano/micro structures known as localize surface plasmon resonance (LSPR) LSPR is a collective oscillation of the electrons of the nano/micro strutures when they are exposed to the light at a specific wavelength Interestingly, this LSPR property of nano/micro structures does not only depend on the die electric constant of the surrounding environment but it also depends on the shape, size and arrangement of the nano/micro structures Therefore, a lot of efforts have been put in controlling the shape, size, and arrangement of nano/micro structures in order to achieve high performance of LSPR property of the nano/micro structures Nano/micro line or wire structures are expected to provide excellent LSPR performance, especially for bio sensing devices [12-14] Effiective methods for fabrication of nano/micro line structures are highy desired for utilizing these structures in bio sensing applications at a low cost Generally, nano/micro line structures are fabricated by the top-down approaches such as electron beam lithography (EBL) [15-16], focus ion beam (FIB) milling [17] and soft-lithography [18-20] However, these methods generally consist of sophisticated steps, they require stringent in controlling the process conditions, and also require costly equipments which result in low throughput, high production cost On the other hand, the bottom-up approaches such as chemical synthesis or anodic aluminum oxide (AAO) mask desposition [21-22] are appropriate for fabrication of nano/micro line or wire structures at low cost However, these methods requires complicated chemical process and using a lot of toxic chemical solutions In Trang 167 HỘI NGHỊ KHCN TOÀN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM order to overcome these disadvantages, in this paper, our group developed a combination process of ultra-precision machining and hot embossing method This method solely utilizes mechanical processes with low cost equipments, simple in controlling, and without toxic chemical The objective of this paper is to verify the feasiblity of this method and demonstration of its capability for fabrication of micro line grooves structure a hard master mold and then imprinting that micro line grooves structure on a plastic film EXPERIMENTAL METHOD Figure shows the proposed process to fabricate micro line grooves strucure on a plastic film This process comprises two steps: (1) micro line grooves structure is fabricated on a hard metal substrate by ultra-precision machining; (2) the micro line grooves structure is imprinted on a plastic film by hot embossing method The lower photographs in Fig illustrate the micro line grooves structure machined on the Ni-P master mold and the micro line grooves structure imprinted on a plastic film by hot embossing The experiments were conducted as follows: Figure Process for fabrication of micro line grooves structure on a plastic film Specimen preparation: A SS400 steel plate was used as a metal substrate It’s surface was polished until the surface roughness lower than Ra 8.0 nm Then the steel substrate was plated with a hard layer of Ni-P alloy by using non-electrolytic plating method The chemical composition of Ni-P alloy was Nikel (N) for 88% and phosphorus (P) for 12% Thickness of Ni-P plating layer was around 20 µm After plating, the Ni-P plating layer was polished again to improve the surface roughness and flatness Roughness of finished surface of the Ni-P layer was Ra 6.3 nm, and flatness was less than 0.2 µm in cutting distance for 10 mm 2.1 Ultra-precision machining structure on master mold of micro line A series of micro line grooves structure was machined on the polished Ni-P layer by using ultra-precision cutting machine Figure (a) Trang 168 shows the ultra-precision cutting machine using in the experiment The machine consists of three axes i.e X, Y and Z axis The feed resolutions are 10 nm for X, Y axis and nm for Z axis The stroke are 40 mm for X and Z axis, and 20 mm for Y axis The movement of the axes was controlled by a computer A cutting tool made of single crystal diamond was mount on Z axis The width of the tool is 0.9 mm The tool rake angle is 0 and the clearance angle is 10 The edge angle of the tool is 90 The tool edge was ground very sharp It’s nose radius is was verify to be less than 50 nm The shape of the diamond tool is shown in figure (c) The cutting force was measured by placing a load cell on Z axis, and the cutting force was recorded by a computer program The cutting length of line grooves are mm, and pitch of the line grooves structure (i.e the distance between line grooves) is μm Cutting speed was 0.4 mm/s and keept constant HỘI NGHỊ KHCN TOÀN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM for all the line grooves Depth of machined line grooves is around 350nm The cutting condition is without any lubrication (dry cutting) Diamond tool Load cell Z stage Cutting direction Diamond tool Ni-P substrate (b) Cutting process Tilt adjustment X,Y stages (a) Ultra-precision cutting machine (c) Diamond tool Figure (a) Ultra-precision cutting machine; (b) Cutting Process; (c) Diamond tool 2.2 Hot embossing of micro line grooves structure from the master mold to a plastic film The micro line grooves structure machined on the Ni-P master mold was used to imprint on a plastic film by hot embossing method The plastic film was made of Cyclo-olefin polymer film (called COP film, Zeon ZF14-100) The thickness of COP film is around 100 µm Figure shows the equiment and the specimen set up for hot embossing The COP film was placed in contact with the Ni-P master mold A quartz glass plate was placed on the COP film to assure the flatness and uniform contact between the COP film and the Ni-P master mold The quartz glass plate, COP film and Ni-P master mold were placed in between the heating plates of the embossing equipment Then both the upper and lower plate were heated to 180C and kept constant during the embossing process The temperture is measure by a thermal sensor After that the load was applied to compress the Ni-P master mold in contact with the COP film The compression load was controlled to MPa and the compression time is maintain for minute Then, the heating plates were cooled down by feeding cool water through the channels inside the heating plates until the their temperature became lower than 40C Finally, the compression load is released The COP film was detacted from the Ni-P master mold A negative micro line grooves structure of the Ni-P master mold was imprinted on the COP film The topology of the micro line grooves structure on the Ni-P master mold and on the COP film was analized by using an AFM (Keyence VN-8010 Hybrid Microscope) Trang 169 HỘI NGHỊ KHCN TOÀN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM Figure Hot embossing equipment and speciment set up RESULTS AND DISCUSSIONS Figure shows AFM images and the cross section of the micro line grooves structure machined on the Ni-P master mold It is confirmed that dense and uniform micro line grooves structure was successfully fabricated on the Ni-P master mold by ultra-precision cutting It is also verified that the pitch of the line grooves structure (i.e the distances between the line grooves) is almost µm, and depths of grooves are 300 ~ 450 nm The average depth of the line grooves is about 354 nm 2µm Figure Micro line grooves structure machined on Ni-P master mold Figure shows AFM images and the cross section of the micro line grooves structure on the COP film fabricated by hot embossing It is found that a negative structure of the line grooves structure on the master mold is successfully imprinted onto the COP film It is also verified that the pitch of the line grooves (i.e the distance between the line grooves ) is almost μm and the heights of crests are from 270 ~ 440 nm and the average heigh of the crests is about 352 nm which is almost the same as pitch and depth of line grooves on the master mold This implies that Trang 170 the micro line grooves structure imprinted on the COP film is high fidelity Interestingly, the Ni-P master mold can be used many times to imprint micro line grooves structure on the plastic films, and later on the plastic film with the micro line grooves structure can be used as a mold for nano/micro imprinting fabrication methods Therefore, it demonstrates that the process is capable for fabrication of micro line grooves structure at high throughput and low production cost HỘI NGHỊ KHCN TOÀN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM 2µm Figure Micro line grooves structure imprinted on COP film by hot embossing CONCLUSION (1) An efficient, low cost, and high throughput fabrication process for micro line grooves structure on a plastic film by combination of ultraprecision machining and hot embossing method was proposed in this paper Its feasibility was demonstrated experimentally (2) Micro line grooves structure with the pitch of µm and an average depth of 354 nm was successfully fabricated on the Ni-P master mold by ultra-precision cutting using a diamond tool (3) A negative micro line grooves structure was successfully inprinted on a COP film by hot embossing method The pitch of the micro line grooves structure on COP film is µm and average height of the crests is 352 nm The imprinted structure is high fidelity ACKNOWLEDGMENT The experiements were conducted in Department of Mechanical Engineering, Tokyo Institute of Technology, Tokyo, Japan The project was support by Hanoi University of Science and Technology (Grant research No T2017-PC-111) and research fellowship from AUN/SEED Net REFERENCES [1] Sagadevan S 2013 Semiconductor Nanomaterials, methods and applications: a review J Nanosci Nanotechnol.3 62-74 [2] Isao M 2005 Nanoparticles for electronic device application: a brief review J Chem Eng Jpn 38 535-46 [3] Katherine, A W., Van Duyne, R P., Localized Surface Plasmon Resonance Spectroscopy and Sensing, Annual Review of Physical Chemistry, Vol 58, 2007, 267297 [4] Sagle, L B., Ruvuna, L K., Ruemmele, J A., Van Duyne, R P, Advances in localized surface plasmon resonance spectroscopy biosensing, Nanomedicine (2011) 6(8), 1447–1462 [5] Yue B Z, Brian K, Paul S W, and Tony J H 2012 Molecular plasmonics for biology and nanomedicine Nanomedicine 751–70 [6] Hao M C and Ru-Shi L 2011 Architecture of metallic nanostructures: synthesis strategy and specific applications J Phys Chem C 115 3513-27 [7] Pillai S., Green M A., Plasmonics for photovoltaic applications, Solar Energy Materials & Solar Cells 94 (2010) 1481– 1486 [8] Wen, L., Xiaodong, W., Yueqiang, L., Zhaoxin, G., Fuhua,Y., Jinmin, L., Surface plasmon enhanced GaAs thin film solar cells, Solar Energy Materials & Solar Cells 95 (2011) 693–698 [9] Chia W H, Bo Z, Wenjun Q, Ofer S, Brendan G D, John D J and Marin S 2014 Transparent displays enabled by resonant nanoparticle scattering Nat Commun.5:3152 1-6 Trang 171 HỘI NGHỊ KHCN TOÀN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM [10] Hongming C, Lei Z, Daqun C, and Weihua H 2015 Stabilization of gold nanoparticles on glass surface with polydopamine thin film for reliable LSPR sensing J Colloid Interface Sci 460 258-263 [11] Willian H, Tiago V A, Caio C S d O, Eduardo G M, Fernando R O, and Pedro H C C 2013 Triangular metal nanoprisms of Ag, Au, and Cu: Modeling the influence of size, composition, and excitation wavelength on the optical properties Chem Phys 423 14250 [12] Tae-E B, Hyun-J J, Jong-H Y, and Won-J C 2013 High Performance of silicon nanowirebased biosensors using a high‑k stacked sensing thin film ACS Appl Mater Interfaces 5214-8 [13] Kirsten M P, A Wouter M , F Burcu C, Ansar A P, Uday K, Bennie t H, and Johan E t E 2013 Au coated Ni nanowires with tuneable dimensions for biomedical applications J Mater Chem B 6129-36 [14] Yurii P I, Ahmed A , Mohammed A , Jose E P, Manuel V, Andrey C, and Jürgen K 2016 Tunable magnetic nanowires for biomedical and harsh environment applications Sci Rep 24198 [15] A M Contreras, J Grunes, X -M Yan, A Liddle, and G A Somorjai 2005 Fabrication of platinum nanoparticles and nanowires by electron beam lithography (EBL) and nanoimprint lithography (NIL): comparison of ethylene hydrogenation kinetics Catal Lett 100 115-24 Trang 172 [16] A Notargiacomo, E Giovine, F Evangelisti, V Foglietti, and R Leoni 2002 EBL- and AFMbased techniques for nanowires fabrication on Si/SiGe Mater Sci Eng., C 19 185-8 [17] D Lucot, J Gierak, A Ouerghi, E Bourhis, G Faini, and D Mailly 2009 Deposition and FIB direct patterning of nanowires and nanorings into suspended sheets of graphene Microelectron Eng 86 882-4 [18] John A R, and Ralph G N 2005 Recent progress in soft lithography Mater Today 50-56 [19] S Y Chou and P R Krauss 1997 Imprint lithography with sub-10 nm feature size and high throughput Microelectron Eng 35 23740 [20] David B S, Daniel A D, Anirudha V S, Ralu D, Suzanne M, Orlando A, Lori A L, Eric A T, Tyler J S, Daryl A F, James P H, and Michael P Z 2011 Electroplate and lift lithography for patterned micro/nanowires using ultrananocrystalline diamond (UNCD) as a reusable template ACS Appl Mater Interfaces 925-30 [21] Rui Y, Chunhong S, Jian G, and Lunyu Q 2007 Silver nanowires prepared by modified AAO template method Mater Lett 61 900-3 [22] S Thongmee, H L Pang, J Ding, and J Y Lin 2009 Fabrication and magnetic properties of metallic nanowires via AAO templates J Magn Magn Mater 321 2712-16 HỘI NGHỊ KHCN TỒN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM CHẾ TẠO CẤU TRÚC RÃNH THẲNG CẤP ĐỘ MICRO TRÊN TẤM MÀNG MỎNG NHỰA BẰNG PHƯƠNG PHÁP GIA CƠNG SIÊU CHÍNH XÁC KẾT HỢP VỚI IN DẬP NÓNG TÓM TẮT: Trong nghiên cứu tác giả trình bày phương pháp hiệu để chế tạo cấu trúc rãnh thẳng cấp độ micro màng mỏng nhựa kết hợp gia cơng siêu xác với phương pháp in dập nóng Phương pháp bao gồm hai bước: trước hết, gia công rãnh micro khuôn Ni-P, sau dùng khn Ni-P để in cấu trúc rãnh thẳng micro lên màng mỏng nhựa phương pháp in dập nóng Kết cho thấy cấu trúc rãnh thẳng với khoảng cách bước khoảng µm chiều cao khoảng 0,35 µm chế tạo thành cơng với độ xác, sắc nét chi phí thấp suất cao phương pháp đề nghiên cứu Tấm khn Ni-P sử dụng nhiều lần để in dập nhiều cấu trúc rãnh thẳng micro màng mỏng nhựa Kết nghiên cứu minh chứng cho việc chế tạo cấu trúc rãnh thẳng xác cao phương pháp gia cơng truyền thống chi phí thấp khơng dùng đến phương pháp đắt đỏ quang khắc Từ khóa: cấu trúc rãnh micro, gia cơng siêu xác, khuôn cái, màng mỏng nhựa Trang 173 ... (1) micro line grooves structure is fabricated on a hard metal substrate by ultra- precision machining; (2) the micro line grooves structure is imprinted on a plastic film by hot embossing method. .. Figure Micro line grooves structure imprinted on COP film by hot embossing CONCLUSION (1) An efficient, low cost, and high throughput fabrication process for micro line grooves structure on a plastic. .. a plastic film by combination of ultraprecision machining and hot embossing method was proposed in this paper Its feasibility was demonstrated experimentally (2) Micro line grooves structure