MICRO AND NANO R2R EMBOSSING OF EXTRUDED POLYMERS

This dissertation presents a process for directly imprinting or embossing extruded polymers as an advancement in roll-to-roll (R2R) embossing methods that avoids the problems of converting preformed films, increases throughput, and reduces costs. A proof-of-concept R2R apparatus was designed and constructed for directly embossing extruded polymer, and experimental results were evaluated. This laboratory scale R2R apparatus employed a thin metal ribbon belt mold with micro or nano scale features in a calendering setup, with a close coupled induction heating (IH) coil to preheat the ribbon mold above glass transition temperature (Tg) of the polymer, prior to contact with the extrudate at the nip of the calender. This allowed the melted polymer to fully fill the mold patterns before starting to solidify. The thin ribbon mold rapidly conducted heat to the calender roller, providing an effective cooling stage. Microscale and nanoscale features were imprinted directly onto extruded polymer film at a rate of 10 to 12 meters per second, three to over one hundred times the throughput of current R2R processes and orders of magnitude faster than planar processes. Metal ribbon mold belts with nano features were needed to test the direct embossing of extruded polymers at the nano scale. Three different avenues were taken to make such ribbon belts. First, preset nickel alloy molds were obtained. A master mold of the Book of Leviticus with letters 6 µm in width, 6 to 9 µm tall and 60-170 nm high and a nickel alloy DVD master mold with track pitch of 740 nm and 105 nm deep Pits between 400 nm and 1900 nm long. These were welded into stainless steel ribbon belts to form belt molds. Second, a process was developed using base forms or mandrels for metal-forming nickel ribbon belt molds with test patterns that included gratings from 70 to 500 nm and pillars having diameters of 1 µm, 700 nm, 500 nm and 350 nm. Third, an investigation of metal glass (MG) as a candidate mold material was undertaken and a laboratory scale mechanism was designed and constructed to emboss metal glass surfaced rollers thermally

Large-Area Nanoimprint Lithography and Applications

Large-area nanoimprint lithography (NIL) has been regarded as one of the most promising micro/nano-manufacturing technologies for mass production of large-area micro/nanoscale patterns and complex 3D structures and high aspect ratio features with low cost, high throughput, and high resolution. That opens the door and paves the way for many commercial applications not previously conceptualized or economically feasible. Great progresses in large-area nanoimprint lithography have been achieved in recent years. This chapter mainly presents a comprehensive review of recent advances in large-area NIL processes. Some promising solutions of large-area NIL and emerging methods, which can implement mass production of micro-and nanostructures over large areas on various substrates or surfaces, are described in detail. Moreover, numerous industrial-level applications and innovative products based on large-area NIL are also demonstrated. Finally, prospects, challenges, and future directions for industrial scale large-area NIL are addressed. An infrastructure of large-area nanoimprint lithography is proposed. In addition, some recent progresses and research activities in large-area NIL suitable for high volume manufacturing environments from our Labs are also introduced. This chapter may provide a reference and direction for the further explorations and studies of large-area micro/nanopatterning technologies

Nanoimprint lithography - the past, the present and the future

Background: Nanoimprinting lithography technique uses a very simple concept of transferring pattern of nanoscale features from a mold to a target substrate. In the past two decades, this technique has successfully broken through the barrier of laboratory scale production and become an industrial scale production technique. The aim of this paper is to introduce to readers to the basic working principle, applications, analysis the technological limitations. It will also point out future research direction of this useful nanofabrication technique. Methods: We adopted a systematic approach to give a comprehensive review of the work principle, hardware and analysis of advantaged and disadvantages of major nanoimprint lithography techniques. Moreover, a technical comparison of these methods is carried out to provide future research direction. Results: 87 papers were reviewed. Four techniques including thermal NIL, ultraviolet light NIL, laser-assisted direct imprint and nanoelectrode lithography have been identified as main stream of NIL techniques. These techniques possess certain advantages and disadvantages in terms of cost, throughput, attainable resolution. Lack of flexibility is the common limitation of current NIL techniques. NIL has gained wide applications in the fabrication of optoelectronics devices, solar cells, memory devices, nanoscale cells, hydrophobic surfaces and bio-sensors. The potential applications of NIL in biochips, artificial organs, diagnostic system, and fundamental research in cell biology will demand large scale 3D fabrication capability with resolution towards 10nm or less. Conclusions: The findings of this review confirm that NIL is one of the most employed commercial platforms for nanofabrication which offers high throughput and cost-effectiveness. One of the disadvantages of NIL over other nanofabrication techniques is the flexibility of patterning. Integrating NIL with other existing nanofabrication techniques can be helpful to overcome such issue. The potential applications of NIL in biochips, artificial organs, diagnostic system, and fundamental research in cell biology will attract researchers to push nanoimprint lithography forward at a resolution of 10 nm or less in the future

Enabling hybrid process metrology in roll-to-roll nanomanufacturing: design of a tip-based tool for topographic sampling on flexible substrates

This work seeks to demonstrate the efficacy of a novel approach for topography measurement of nano-scale structures fabricated on a flexible substrate in a roll-to-roll (R2R) fashion. R2R manufactured products can be extremely cost competitive compared to more traditional, silicon wafer or glass panel based nanofabrication solutions, in addition to the unique and often desirable mechanical properties inherent to flexible substrates. As such, flexible nanomanufacturing is an area of immense research interest. However, despite the significant potential of these products for a variety of applications, developing manufacturing systems from lab-scale prototypes to pilot- or high volume manufacturing (HVM) has often proven both difficult and infeasibly expensive as research investment and achievable process yield limit advancement. One of the most significant capability gaps in current art, and roadblocks on the path towards adoption of R2R nanomanufacturing, is the lack of high-throughput, nanometer-scale metrology for process development, real-time control, and yield enhancement. This dissertation presents the design of a tip-based measurement tool implementing atomic force microscope (AFM) probes manufactured with a micro-electro-mechanical system (MEMS) approach to the challenge of sub-micron topography measurement which is also compatible with R2R manufacturing on flexible substrates. A proof-of-concept prototype tool with subsystems to regulate a flexible web, isolate and position the atomic force microscope probe, and measure features on the substrate, all coordinated by a real-time embedded control system, was designed and fabricated. The positioning subsystem was evaluated dynamically to ensure initial design requirements were met, and stationery, step-and-scan results were presented. However, to wholly meet this extent need for in-line R2R metrology, a system capable of atomic force microscope scanning despite a continuous, non-zero substrate velocity is required - any regular stoppage of the web in a R2R process all but dooms economically viable production throughput. Refinement and redesign of the proof-of-concept tool was driven by new system requirements to meet this goal, in addition to lessons learned from the initial prototype. Improvements focused on upgrading the web handling spindle design and mechatronics, tool power electronics, moving structures, and control algorithms used for high-speed synchronous positioning of the atomic force microscope and web. The culmination of this work will serve to introduce a new measurement framework which may be used to accelerate and enable future research in R2R manufacturing of nanofeatured products.Mechanical Engineerin

Nanoimprint Lithography: Methods and Material Requirements

Nanoimprint lithography (NIL) is a nonconventional lithographic technique for high-throughput patterning of polymer nanostructures at great precision and at low costs. Unlike traditional lithographic approaches, which achieve pattern definition through the use of photons or electrons to modify the chemical and physical properties of the resist, NIL relies on direct mechanical deformation of the resist material and can therefore achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in conventional techniques. This Review covers the basic principles of nanoimprinting, with an emphasis on the requirements on materials for the imprinting mold, surface properties, and resist materials for successful and reliable nanostructure replication.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55959/1/495_ftp.pd

Technologies for printing sensors and electronics over large flexible substrates: a review

Printing sensors and electronics over flexible substrates is an area of significant interest due to low-cost fabrication and possibility of obtaining multifunctional electronics over large areas. Over the years, a number of printing technologies have been developed to pattern a wide range of electronic materials on diverse substrates. As further expansion of printed technologies is expected in future for sensors and electronics, it is opportune to review the common features, complementarities and the challenges associated with various printing technologies. This paper presents a comprehensive review of various printing technologies, commonly used substrates and electronic materials. Various solution/dry printing and contact/non-contact printing technologies have been assessed on the basis of technological, materials and process related developments in the field. Critical challenges in various printing techniques and potential research directions have been highlighted. Possibilities of merging various printing methodologies have been explored to extend the lab developed standalone systems to high-speed roll-to-roll (R2R) production lines for system level integration

Understanding and developing capabilities for large area and continuous micro contact printing

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 141-143).Micro contact printing is a high spatial resolution-patterning tool that can be used for printing on large and non-planar surfaces because of which it has begun to find important applications in printed organic electronics and fiber optics. However, problems like achieving precise alignment and registration, air bubble trapping and low production rate still remain unresolved. The goal of this thesis is to conceptualize and implement a low cost solution to these problems to be used by a nano-technology based company in Cambridge, Massachusetts. In this dissertation, we first present an extensive literature review of soft lithography techniques, focusing more on micro-contact printing and critical factors for taking this technology from laboratory to commercial production. We then introduce another printing technique called flexography and discuss how this method when combined with micro contact printing can help in overcoming the above stated limitations and at the same time achieve high throughput rate at low cost. We propose a Flexography style micro contact printing mechanism with rotating cylindrical stamps enabling reel to reel processing. Finally, results from the experiments conducted to study the effect of parameters like ink concentration, speed and pressure on the print quality are documented.by Ambika Goel, Sowmya Laxminarayanan and Yun Xia.M.Eng

ELECTROPHORESIS IN HETEROGENEOUS HYDROGELS AND APPLICATIONS IN SURFACE PATTERNING

The creation of chemical micropatterns on surfaces makes it possible to add unique chemical functionality to surfaces, modifying properties such as wettability, or even adding the ability to selectively bind other molecules. The creation of biochemical surface patterning in particular is useful in a variety of fields including tissue engineering and highthroughput drug screening. There are many existing surface patterning techniques which focus on precise control over the patterned geometry, even down to submicron scale features, but they do not allow local control over chemical concentration. So the results are high resolution patterns with binary concentration. There are also existing methods to generate surface gradients of chemicals, but the focus there is to produce unidirectional concentration variation over a large surface. Normally these two methods—surface patterning and surface gradient generation—are incompatible with each other. So despite the large number of applications where simultaneous control over chemical placement and concentration would be useful, there is a dearth of options for doing so. In addition, it would be valuable to make micro patterned surfaces in a simple and approachable way, because fields where it could be most beneficial (such as tissue culture) are populated by individuals who are typically not microfabrication experts. The goal of this research is to develop an easy and low cost method for creating biochemical surface patterns with microscale feature resolution and local control over chemical concentration. The method described here leverages the force on charged protein molecules in an electric field to drive the molecules in a given direction. The speed with which these molecules move depends on the properties of the molecules themselves and the medium through which they travel. By creating a material with heterogeneous regions—in this work, a hydrogel with different mesh densities—it is possible to have local spatial control over the speed of protein movement. In this work, this concept was used to drive biomolecules (proteins) onto a target paper surface, and then local protein concentration was measured using fluorescence or intensity of a protein stain. In addition, these patterns were achieved using materials and methods that are easily accessible to individuals in most biochemical or tissue culture laboratories

From Cleanroom to Desktop: Emerging Micro-Nanofabrication Technology for Biomedical Applications

This review is motivated by the growing demand for low-cost, easy-to-use, compact-size yet powerful micro-nanofabrication technology to address emerging challenges of fundamental biology and translational medicine in regular laboratory settings. Recent advancements in the field benefit considerably from rapidly expanding material selections, ranging from inorganics to organics and from nanoparticles to self-assembled molecules. Meanwhile a great number of novel methodologies, employing off-the-shelf consumer electronics, intriguing interfacial phenomena, bottom-up self-assembly principles, etc., have been implemented to transit micro-nanofabrication from a cleanroom environment to a desktop setup. Furthermore, the latest application of micro-nanofabrication to emerging biomedical research will be presented in detail, which includes point-of-care diagnostics, on-chip cell culture as well as bio-manipulation. While significant progresses have been made in the rapidly growing field, both apparent and unrevealed roadblocks will need to be addressed in the future. We conclude this review by offering our perspectives on the current technical challenges and future research opportunities

Meso scale component manufacturing: a comparative analysis of non-lithography and lithography-based processes

The paper identifies the meso scale (10 µm to few millimeters) component size that can be manufactured by using both lithography and non-lithography based approaches. Non-lithography based meso/micro manufacturing is gaining popularity to make micro 3D artifacts with various engineering materials. Being in the nascent stage, this technology looks promising for future micro manufacturing trends. Currently, lithography based micro manufacturing techniques are mature, and used for mass production of 2D, 2.5D features and products extending to 3D micro parts in some cases. In this paper, both the techniques at state-of-the-art level for meso/micro scale are explained first. The comparison is arranged based on examples and a criterion is set in terms of achievable accuracy, production rate, cost, size and form of artifacts and materials used. The analysis revealed a third combined approach where a mix of both techniques can work together for meso scale products. Critical issues affecting both the manufacturing approaches, to advance in terms of accuracy, process physics, materials, machines and product design are discussed. Process effectiveness guideline with respect to the component scale, materials, achievable tolerances, production rates and application is emerged, as a result of this exercise