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Imprint Lithography
Published in Bruce W. Smith, Kazuaki Suzuki, Microlithography, 2020
Nanoprinting (known as microcontact printing [µCP] [12]), in contrast to nanoimprinting, transfers an ink from stamp surface protrusions onto a substrate. Such an ink consists of (linear) chain molecules with the ability to adhere or bind to surface atoms, which often create monomolecular films that—due to their density and chemical properties—can act as resists. However, such films, in the case of self-assembled monolayers (SAMs) only 1 to 2 nm thick, present chemical contrast rather than topographical contrast against typical etchants (see Table 11.1). This process has demonstrated sub-100 nm resolution and in principle, can pattern structures with similar resolution to NIL, if lateral diffusion of densely printed molecules is inhibited. While NIL is clearly directed toward high-resolution applications, µCP is for research applications, mostly in the area of biotechnology. The main criteria for this are resolution, throughput, and the possibility to integrate the process into existing process chains.
Nanofabrication Techniques
Published in Wesley C. Sanders, Basic Principles of Nanotechnology, 2018
Two of the most common forms of soft lithography are microcontact printing and micromolding in capillaries (Lyman et al. 2010). Microcontact printing involves the transfer of molecular patterns onto the surface of substrates by making direct contact between an inked stamp and a flat substrate (Figure 8.3). The most commonly used “ink” for microcontact printing is an alcohol-based solution of alkanethiols (Lyman et al. 2010). This technique involves the use of protrusions on the surface of an inked elastomeric stamp to pattern structures on flat substrates (Figure 8.4) (Sanders 2015).
Nanofabrication Techniques with High-Resolution Molded Rubber Stamps
Published in Ahmed Busnaina, Nanomanufacturing HANDBOOK, 2017
Some of the simplest types of patterning methods, such as those based on embossing, molding, stamping, writing, etc., are now being re-examined for use in nanofabrication. The development of new materials and chemistries has revealed an impressive potential of these techniques to fabricate structures at the nanoscale level.3 Some of the efforts in this field began with the development of methods for generating high-resolution molded rubber “stamps.”4 These soft stamps enable the accurate replication of patterns with nanometer-scale dimensions on the surface of a master (i.e., a surface with structured relief).5,6 These new methods, collectively referred to as “soft lithographic” techniques, now represent a field of research on its own, with active groups worldwide. The first soft lithographic technique relies on the use of a molded stamp that is inked with a chemical ink. Similar to a conventional stamping process, the inked stamps can come into contact with a target substrate in order to transfer patterns of ink in the geometries of the raised area of the stamps. Several low-diffusion chemical inks with an ability to form densely packed self-assembled monolayers on the target substrate surface have been successfully used.7 These inked patterns typically serve as resists for wet etching of the underlying material (usually metals). The invention of the micro-contact printing (µCP) method, led initially by the Whitesides group at Harvard University, has generated considerable interest mainly because of the ability of this technique to generate submicron patterns in a nonclean room environment. The ease with which this patterning technique can be performed, without expensive facilities, also facilitated its fast spread across several scientific research fields. Microcontact printing relies critically on the ability of the rubber stamps to form intimate contact (i.e., without air voids) with a range of surfaces, including those that have some degree of roughness. Some of the fundamental aspects of this “wetting” phenomenon are still not well understood. Recent studies, however, are beginning to yield insights into this process by adapting theories developed for adhesion forces and crack propagation.8,9
Development of microstructured fish scale collagen scaffolds to manufacture a tissue-engineered oral mucosa equivalent
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Ayako Suzuki, Hiroko Kato, Takahiro Kawakami, Yoshihiro Kodama, Mayuko Shiozawa, Hiroyuki Kuwae, Keito Miwa, Emi Hoshikawa, Kenta Haga, Aki Shiomi, Atsushi Uenoyama, Issei Saitoh, Haruaki Hayasaki, Jun Mizuno, Kenji Izumi
Microcontact printing, photolithography, and laser patterning have been introduced as micropatterning techniques for glass or plastic culture substrates [23]. Recently, Yu et al. reported a micromilling technology to create PDMS molds, followed by the fabrication of hydrogel scaffolds with 3 D undulated microtopographies mimicking the dermal papilla in the skin [9]. In the present study, we reported a novel approach for constructing tilapia scale type I collagen scaffolds with 3 D microtopographic structures mainly involving the following three processing steps (Figure 2): (1) manufacturing of a silicon semiconductor substrate with a combination of anisotropic and isotropic etching, (2) fabrication of four different types of negative molds made of PDMS or Si, (3) fabrication of microstructured fish scale collagen scaffolds. This semiconductor process allows any configurations of microstructure fabrication mimicking the connective tissue papilla of the oral mucosa because of anisotropic etching that has shape controllability, such as steep undulation and isotropic etching, which allows fabrication of truncated micropatterns. In addition, this semiconductor process could serve as a high-throughput technique useful in manufacturing off-the-shelf biomaterials in regenerative medicine.
Area-selective atomic layer deposition of Al2O3 using inkjet-printed inhibition patterns and lift-off process
Published in Journal of Information Display, 2023
Jun Ho Yu, Young–In Cho, Jae–Wook Lee, Kyung Hyun Choi, Sang–Ho Lee
Photolithography-based lift-off processes or microcontact printing are generally used to pattern SAMs for AS-ALD [8,23–26]. However, since a typical SAM is ∼2 nm thick, it is quite challenging to fabricate features thicker than a few nanometers [5]. The increase in film thickness over the height of SAM during ALD leads to lateral film overgrowth [3,5]. Furthermore, it is important to form a defect-free SAM to effectively block the growth of films during ALD [3]. It usually takes more than 24 h to obtain a well-packed SAM by immersion of the sample in solution or by vapor deposition [27]. In the case of polymer films, spin coating and photolithography-based lift-off processes can be used to easily control the thickness of ALD-inhibition patterns and obtain thicker polymer films [7,9,28]. The inkjet printing process was introduced as an alternative patterning method to pattern polymer thin films for AS-ALD [9,20]. This process was transformed into a sophisticated device manufacturing method for low-cost, large-area, and flexible electronics [29]. One of the main advantages of this process is the ability to position the material on planar and non-planar substrates using computer control to produce structures without the need for photomasks [30]. The inkjet printing process can control the thickness of the target materials at the desired position using an overprinting technique. By increasing the number of the inkjet head, various materials can be printed simultaneously and multi-layered patterns can be realized by layer–by–layer printing. The inkjet printing process is less time-consuming to form mask patterns for AS-ALD when compared to the film patterning methods of both SAMs and polymers.