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Wei W, Li M, Chen Y. Flexible Broadband Light Absorbers with a Superhydrophobic Surface Fabricated by Ultraviolet-assisted Nanoimprint Lithography. Chem Res Chin Univ 2022. [DOI: 10.1007/s40242-022-2044-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Sun B, Zhao Y, Wu W, Zhao Q, Li G. A superhydrophobic chip integrated with an array of medium reservoirs for long-term hanging drop spheroid culture. Acta Biomater 2021; 135:234-242. [PMID: 34389482 DOI: 10.1016/j.actbio.2021.08.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 08/04/2021] [Accepted: 08/05/2021] [Indexed: 01/24/2023]
Abstract
Hanging drop (HD) is one of the most popular methods used for forming three-dimensional (3D) cell spheroids. However, conventional hanging drop systems are only applicable for short-term spheroid culture due to their inconvenience in exchanging cell culture media. Here we present a medium-reservoir-integrated superhydrophobic (MRI-SH) chip for long-term HD spheroid cultures. The device consists of two main components: i) a patterned superhydrophobic (SH) surface containing an array of wettable spots which anchor arrays of droplets of cell suspension, and ii) an array of chambers that serve as medium reservoirs, both interconnected via an array of thru-holes. This configuration provides two distinct advantages over conventional HD configurations: i) the high wettability contrast of the SH pattern on the chip leads to the formation and adhesion of nearly spherical hanging droplets on its surface, which minimizes interactions between the liquid and the substrate; ii) the integrated chambers provide large volumes of medium to maintain longer culture durations. Using this device, spheroids of MHCC97H cells were successfully formed, and the cultured spheroids could maintain high viability for up to 30 days and exhibited enhanced spheroid morphology compared to those cultured in the conventional HD systems. STATEMENT OF SIGNIFICANCE: This paper presents a medium-reservoir-integrated superhydrophobic hanging drop (HD) platform for the long-term culture of spheroids with enhanced morphology. By monolithically integrating medium reservoirs and a patterned SH surface into a single device, this HD platform can not only produce high-quality spheroids, but also permit them to sustain high viability for up to 30 days without the need for tedious medium replenishment. We believe that such a platform will be valuable in a wide range of biological or biomedical applications, including tissue engineering, regenerative medicine, and drug discovery.
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Affiliation(s)
- Bangyong Sun
- Key Laboratory of Optoelectronic Technology and Systems, Ministry of Education, Defence Key Disciplines Lab of Novel Micro-Nano Devices and System Technology, Chongqing University, Chongqing 400044, China
| | - Yi Zhao
- Chongqing Key Laboratory of Translational Research for Cancer Metastasis and Individualized Treatment, Chongqing University Cancer Hospital, Chongqing, 400030, China
| | - Weimin Wu
- School of Mechanical and Power Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
| | - Qiang Zhao
- Key Laboratory of Optoelectronic Technology and Systems, Ministry of Education, Defence Key Disciplines Lab of Novel Micro-Nano Devices and System Technology, Chongqing University, Chongqing 400044, China
| | - Gang Li
- Key Laboratory of Optoelectronic Technology and Systems, Ministry of Education, Defence Key Disciplines Lab of Novel Micro-Nano Devices and System Technology, Chongqing University, Chongqing 400044, China.
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Interfacial Interactions during Demolding in Nanoimprint Lithography. MICROMACHINES 2021; 12:mi12040349. [PMID: 33805114 PMCID: PMC8064091 DOI: 10.3390/mi12040349] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 03/02/2021] [Accepted: 03/10/2021] [Indexed: 11/17/2022]
Abstract
Nanoimprint lithography (NIL) is a useful technique for the fabrication of nano/micro-structured materials. This article reviews NIL in the field of demolding processes and is divided into four parts. The first part introduces the NIL technologies for pattern replication with polymer resists (e.g., thermal and UV-NIL). The second part reviews the process simulation during resist filling and demolding. The third and fourth parts discuss in detail the difficulties in demolding, particularly interfacial forces between mold (template) and resist, during NIL which limit its capability for practical commercial applications. The origins of large demolding forces (adhesion and friction forces), such as differences in the thermal expansion coefficients (CTEs) between the template and the imprinted resist, or volumetric shrinkage of the UV-curable polymer during curing, are also illustrated accordingly. The plausible solutions for easing interfacial interactions and optimizing demolding procedures, including exploring new resist materials, employing imprint mold surface modifications (e.g., ALD-assisted conformal layer covering imprint mold), and finetuning NIL process conditions, are presented. These approaches effectively reduce the interfacial demolding forces and thus lead to a lower defect rate of pattern transfer. The objective of this review is to provide insights to alleviate difficulties in demolding and to meet the stringent requirements regarding defect control for industrial manufacturing while at the same time maximizing the throughput of the nanoimprint technique.
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Amirsadeghi A, Brumfield L, Choi J, Brown E, Lee JJ, Park S. The role of hydrophobic silane coating on Si stamps in nanoimprint lithography. JOURNAL OF APPLIED PHYSICS 2017; 121:044909. [PMID: 29632415 PMCID: PMC5881421 DOI: 10.1063/1.4974533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 01/04/2017] [Indexed: 06/08/2023]
Abstract
Hydrophobic silane coatings have been successfully applied to the surface of Si stamps to improve demolding in nanoimprint lithography (NIL). However, the role of the silane coating has only been studied either indirectly, by measuring adhesion or friction coefficients for Si and substrate surfaces without patterns, or collectively, by measuring the overall demolding force that does not differentiate contributions of friction dissipation, stored elastic energy, and adhesion. Here, for the first time, we present experimental evidence on the role of the silane coating in improving demolding in UV-NIL by using different silane coatings. The silane coatings were characterized by x-ray photoelectron spectroscopy, water contact angle, and friction force measurements. Then, the work of demolding was systematically measured for different silane coatings using stamps with the same micropattern but different pattern depths. Comparison of the results to the theoretical model developed for fiber-matrix debonding energy by Sutcu and Hillig [Acta Metall. Mater. 38(12), 2653-2662] indicated that with a hydrophobic silane coating, the main parameter contributing to overall demolding work shifts from adhesion to stored elastic energy and frictional dissipation as surface adhesion keeps decreasing. The results confirm that the main role of the silane coating in reducing the demolding is to reduce surface adhesion rather than friction at the stamp/substrate interface.
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Affiliation(s)
- Alborz Amirsadeghi
- Mechanical Engineering Department and Center of Bio-Modular and Multi-scale Systems, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Lance Brumfield
- Mechanical Engineering Department and Center of Bio-Modular and Multi-scale Systems, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Junseo Choi
- Mechanical Engineering Department and Center of Bio-Modular and Multi-scale Systems, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Emily Brown
- Mechanical Engineering Department and Center of Bio-Modular and Multi-scale Systems, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Jae Jong Lee
- Nano-Mechanical Systems Research Division, Korea Institute of Machinery and Materials, 104 Sinseongno, Yuseong-Gu, Daejeon 305-343, South Korea
| | - Sunggook Park
- Mechanical Engineering Department and Center of Bio-Modular and Multi-scale Systems, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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Zhang R, Wang Q, Zheng X, Ma L, Zhang J. Effects of Friction Coefficient and Cohesion between a Mold and a Polymer Resist during Demolding Process in Hot Embossing. J PHOTOPOLYM SCI TEC 2016. [DOI: 10.2494/photopolymer.29.39] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Rui Zhang
- Shandong University of Science and Technology
- Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation
| | - Qing Wang
- Shandong University of Science and Technology
- Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation
| | - Xu Zheng
- Shandong University of Science and Technology
- Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation
| | - Lijun Ma
- Shandong University of Science and Technology
- Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation
| | - Jintao Zhang
- Shandong University of Science and Technology
- Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation
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Amirsadeghi A, Lee JJ, Park S. A simulation study on the effect of cross-linking agent concentration for defect tolerant demolding in UV nanoimprint lithography. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:11546-11554. [PMID: 22780100 DOI: 10.1021/la300256k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The chemistry and composition of UV-sensitive resists are key factors determining the stress in the molded resist structure in UV nanoimprint lithography (UV-NIL) and thus the success of the process. The stress in the molded structure is mainly generated due to shrinkage of the resist in the UV curing step and also adhesion and friction at the stamp/resist interface in the subsequent demolding step. Thus, understanding of the stress generated in these steps is critical to the improvement of the process as well as the development of new UV resists. In this paper the effect of resist composition on the stress generation was studied by numerical simulations of the curing and demolding steps in UV-NIL. Parameters required for the simulation, such as resist shrinkage, Young's modulus, fracture strength, friction coefficient, crack initiation stress, and debonding energy, were determined experimentally for different resist compositions. As the cross-linking agent concentration increases the fracture strength also improves. In addition, as more cross-linking agent is added to the resist composition, both shrinkage stress due to the curing and also adhesion at the stamp/resist interface increase resulting in a larger maximum local stress experienced by the resist on demolding. By normalizing the overall maximum local stress by the fracture stress of the resist, we found that there is an optimum for the cross-linking agent concentration that leads to the most successful imprinting. Our finding is also corroborated by qualitative experimentations performed for UV-NIL with various resist compositions.
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Affiliation(s)
- Alborz Amirsadeghi
- Mechanical Engineering Department, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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YEO LP, LAM YC, CHAN-PARK MARYB, JOSHI SC, HARDT DE. DEMOLDING OF HIGH ASPECT RATIO POLYMERIC MICRO-PATTERNING. INTERNATIONAL JOURNAL OF NANOSCIENCE 2011. [DOI: 10.1142/s0219581x05003462] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
UV embossing for polymeric micro-patterning thin film is an emerging replication technique. This paper investigates UV curable multifunctional acrylates pre-polymer resin patterned by a micro-structured mold and subsequently cured by UV irradiation. To further enhance this duplication method for high aspect ratio production, demolding must be reliable and repeatable without damage to the embossing or mold. Previously, it has been reported that UV embossed patterns for aspect ratios as high as 14 have been achieved experimentally. Finite element analyses for patterns with aspect ratios of 5 using parallel demolding between two parallel plates have also been reported. However, the parallel demolding method may not be suitable for large area patterns as forces generated were high. As such, an alternative demolding method, namely peel demolding, for micro-patterns with an aspect ratio of 14 was investigated and key parameters identified. The parameters governing the demolding process were the peel angle, the pre-crack condition, shrinkage, interface fracture toughness, tensile strength and modulus of polymer. A pre-crack between the polymer and mold was introduced before peel demolding. Numerical analyses in terms of Cohesive Zone Modeling (CZM) were used to simulate the demolding process. Shrinkage caused by UV exposure was represented by thermal strain effects and the fully cured polymer was peeled off using displacement control. The ultimate tensile strength (U.T.S) of the cured polymer was used as a failure criterion. The stresses involved were crucial for determining clean demolding. As peeling progressed, stresses experienced in the polymer matrix increased rapidly in the region ahead of the crack with little or no stress at the cracked region. When stresses experienced by the polymer were below the U.T.S, demolding was deemed to be successful.
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Affiliation(s)
- L. P. YEO
- The Singapore-MIT Alliance, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Y. C. LAM
- The Singapore-MIT Alliance, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 693798, Singapore
| | - MARY B. CHAN-PARK
- The Singapore-MIT Alliance, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 693798, Singapore
- School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - S. C. JOSHI
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 693798, Singapore
| | - D. E. HARDT
- The Singapore-MIT Alliance, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-430, USA
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Effects of exposure time on defects and demolding force in soft ultraviolet nanoimprint lithography. ACTA ACUST UNITED AC 2009. [DOI: 10.1116/1.3186611] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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del Campo A, Arzt E. Fabrication Approaches for Generating Complex Micro- and Nanopatterns on Polymeric Surfaces. Chem Rev 2008; 108:911-45. [PMID: 18298098 DOI: 10.1021/cr050018y] [Citation(s) in RCA: 379] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Aránzazu del Campo
- Max-Planck-Institut für Metallforschung, Heisenbergstraβe 3, 70569 Stuttgart, Germany
| | - Eduard Arzt
- Max-Planck-Institut für Metallforschung, Heisenbergstraβe 3, 70569 Stuttgart, Germany
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Gaubert HE, Frey W. Highly parallel fabrication of nanopatterned surfaces with nanoscale orthogonal biofunctionalization imprint lithography. NANOTECHNOLOGY 2007; 18:135101. [PMID: 21730372 DOI: 10.1088/0957-4484/18/13/135101] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Large areas of nanopatterns of specific chemical functionality are needed for biological experiments and biotechnological applications. We present nanoscale orthogonal biofunctionalization imprint lithography (NOBIL), a parallel top-down imprinting and lift-off technique based on step-and-flash imprint lithography (SFIL) that is able to create centimetre-scale areas of nanopatterns of two biochemical functionalities. A photoresist precursor is polymerized with a template in place, and the thin resist layer is etched to create an undercut for lift-off. Gold nano-areas on a silicon dioxide background are then independently functionalized using self-assembly that translates the nanopattern into a cell-adhesive/cell-rejective functionality pattern. We demonstrate the technique by creating fibronectin areas down to a pattern size of 60 nm against a polyethylene glycol (PEG) background, and show initial results of cells stably seeded over an array of 1 mm(2) areas of controlled size and pitch.
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Affiliation(s)
- Harold E Gaubert
- Department of Biomedical Engineering and Center for Nano and Molecular Science and Technology, The University of Texas at Austin, 1 University Station, C0800, Austin, TX 78712, USA
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Zhou WX, Chan-Park MB. Large area UV casting using diverse polyacrylates of microchannels separated by high aspect ratio microwalls. LAB ON A CHIP 2005; 5:512-518. [PMID: 15856087 DOI: 10.1039/b419330j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Large area molding of long and deep microchannels separated by high aspect ratio microwalls is important for high sensitivity and high throughput microfluidic devices. Ultraviolet (UV) casting is a feasible, economical and convenient method of replication of such microstructures in plastics. It is shown that a wide variety of polyacrylates with diverse properties such as those made from epoxy (EP), polyurethane (UR), polyester (ES), poly (ethylene glycol) (EG) and poly(propylene glycol) (PG) can be used for the high aspect ratio (7-9) UV casting of such linear microstructures over a 100 mm diameter, enlarging the range of applications of the replicated microstructures. Some challenges arise. With the EG formulation, wavy microstructures were observed; this can be overcome by stress relaxation. With non-polar PG formulation, poor adhesion between the polyester substrate and resin can lead to delamination of the casting from the substrate during demolding; this can be overcome by pre-coating a partially cured same resin on the polyester substrate. An optimum UV irradiation time was important for cure at the deepest end of the microstructure without excessive crosslinking leading to much increased demolding forces. The viscosity and wetting capability of the formulations were found to affect replication fidelity.
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Affiliation(s)
- W X Zhou
- The Biological and Chemical Process Engineering Laboratory, The School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
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