High aspect ratio polymer micro/nano-structure manufacturing using nanoembossing, nanomolding and directed self-assembly (original) (raw)
Nanomolding based fabrication of synthetic gecko foot-hairs
2002
Abstract This paper proposes two different nanomolding methods to fabricate synthetic gecko foot-hair nanostructures. The first method uses an atomic force microscope (AFM) probe indented flat wax surface and the second one uses a nano-pore membrane as a template. These templates are molded with silicone rubber, polyimide and polyester type polymers under vacuum and the template is peeled off or etched away.
Synthetic gecko foot-hair micro/nano-structures as dry adhesives
2003
This paper proposes techniques to fabricate synthetic gecko foot-hairs as dry adhesives for future wall-climbing and surgical robots, and models for understanding the synthetic hair design issues. Two nanomolding fabrication techniques are proposed: the first method uses nanoprobe indented flat wax surface and the second one uses a nano-pore membrane as a template. These templates are molded with silicone rubber, polyimide, etc. type of polymers under vacuum.
Fabrication of biomimetic gecko setae by direct photolithography and micromolding processes
2011 6th IEEE International Conference on Nano/Micro Engineered and Molecular Systems, 2011
In nature, geckos have developed complex adhesion structures capable of smart adhesion, the ability to cling to different smooth and rough surfaces, even ceilings, and detach at will. The hierarchical structure of gecko foot hair, consisting of microscale setae, branches and nanoscale spatula, contributes to the strong adhesion on different surfaces. In this paper, we present two approaches to fabricating high-aspect-ratio polymer fiber arrays mimicking gecko setae. SU-8 photoresist has been applied, and SU-8 fiber arrays with aspect ratio of 10 were obtained. Polydimethyl-siloxane (PDMS) microfiber arrays were fabricated through a micromolding process and the master template for this process was fabricated by using inductively coupled plasma (ICP) technology. The contact angle of water droplets on PDMS microfiber arrays shows increased hydrophobic property of PDMS microfiber arrays than nonpatterned PDMS surface, from 102° to 137°.
Synthetic gecko foot-hair micro/nano-structures for future wall-climbing robots
Proceedings - IEEE International Conference on Robotics and Automation, 2003
This paper proposes techniques to fabricate synthetic gecko foot-hairs as dry adhesives for future wallclimbing and surgical robots, and models for understanding the synthetic hair design issues. Two nanomolding fabrication techniques are proposed: the first method uses nanoprobe indented flat wax surface and the second one uses a nano-pore membrane as a template. These templates are molded with silicone rubber, polyimide, etc. type of polymers under vacuum. Next, design parameters such as length, diameter, stiffness, density, and orientation of hairs are determined for non-matting and rough surface adaptability. Preliminary micro/nano-hair prototypes showed adhesion close to the predicted values for natural specimens (around 100 nN each).
Replication of Micro- and Nanostructures on Polymer Surfaces
Macromolecular Symposia, 2010
Via geometrical micro-and nanostructures new functionalities like controlled wetting properties, biological adhesive / dehesive properties or surface patterns for guided self assembly can be added to polymer surfaces. This is especially interesting for medical or biotechnological applications, because there is no new approval process necessary. The whole process from producing the structures via EUV-interference lithography to the injection moulding will be shown. How far the limits for the smallness of these structures on polymers are already pushed forward show the results from our latest injection moulded samples. Grooves of 18 nm widththis means world record!-could be reproduced in an industrial process and in an economical very interesting high-volume production.
Fabrication of a gecko seta-like structure using polydimethylsiloxane
International Journal of Adhesion and Adhesives, 2012
This study proposes the combination of electrochemical tip sharpening, mirror wax plate production, computer numerical control (CNC) imprinting technology, and the polydimethylsiloxane (PDMS) vacuum casting method to produce an innovative process akin to the setae arrangement in gecko feet to create a large-area gecko seta-like structure or gecko tape. This study produced micrometer tip radius probes using electrochemical methods and used CNC to apply imprinting technology to imprint a micrometer pore structure on the mirror wax plate (substrate) via micro-scale probes to be covered with a micro-porous structure of the wax mold, conducting the vacuum casting method by PDMS to create a gecko tape shaped like gecko feet. The results show that the surface roughness of the mirror wax plate produced in this study reaches the nanoscale. After electrochemical tip sharpening, the tip radius of the 0.5 mm tungsten rod can be reduced to less than 10 mm. The finished gecko tape indicates that using a wax mold to conduct PDMS vacuum casting creates good formability. This indicates the innovative gecko seta-like tape process proposed in this study is greatly feasible. It was also found that the adhesion force increased with the increase of the number of pillars and the increased pillars height of the gecko tape. The average adhesion force of a single pillar, however, decreases with an increase in the number of pillars.
Injection moulding of ultra high aspect ratio nanostructures using coated polymer tooling
Journal of Micromechanics and Microengineering, 2014
Replication-based nanofabrication techniques offer rapid, cost effective ways to produce nanostructured devices for a host of applications in engineering, biological research and beyond. In this work we developed a method to replicate ultra high aspect ratio (UHAR) nanopillars by injection molding with failure rates lower than one pillar in a thousand. We provide a review of the literature in which replication of difficult micro-and nanostructures is facilitated through the use of different tooling materials and surface coatings, before describing the non-adhesive surface coatings which we used to translate a previously developed technique from low to high aspect ratios. This development involved a systematic study of nine different surface coatings on polymer tooling initially patterned by nanoimprint lithography. Using this method we were able to produce injection moulded pillar-like nanostructures with aspect ratios of up to 20:1, more than 6 times that reported elsewhere in the literature for this type of feature.
Fabrication of difficult nanostructures by injection moulding
2013
There is an increasing demand for nanostructured polymeric surfaces for many scientific and commercial applications including the fields of cell and tissue engineering, where the study of the ways that cells interact with their environment holds great potential for the future of regenerative medicine. Current replication based fabrication techniques, such as hot embossing, which are used to produce nanostructured surfaces for this type of research are not fast enough to keep up with the growing demand for them. Injection moulding offers a high throughput alternative to these processes and can upscale the production of nanopatterned samples by several orders of magnitude. However, the nickel moulds traditionally used to injection mould micro-and nanostructures are limited to producing recessed features due to the rate at which the injected polymer cools upon contact with it. In order to replicate raised features (e.g. pillars) the polymer needs enough time to fill the nanoscale cavities of the mould before freezing. A solution to this limitation of nickel tooling is devised and implemented, using a thermally insulating tooling material that facilitates the formation of nanopillars by injection moulding. This tooling material can be patterned by a range of fabrication techniques including photolithography and nanoimprint lithography. The tooling can be used to replicate nanopatterns over underlying micron and millimetre scale topographies. This flexible solution enables the large volume production of samples containing raised poly(carbonate) nanopillars without significantly compromising cycle time. Following this, the technique is adapted in an attempt to replicate high aspect ratio nanostructures. In this section a range of non-adhesive surface coatings are tested for their abilities to enhance the replication process through the systematic analysis of their durability and the replication fidelity that they enable. Nanopillars with aspect ratios of greater than 10:1 are successfully produced and are used to fabricate surfaces for cell engineering research. This success is also demonstrative of the technique's potential to mass produce nanostructures for other applications such as non-reflective and dry adhesive surfaces. Finally, a study is undertaken to replicate microstructures with an elastomeric polymer. The tooling solution is used to assess the minimum feature size that can be replicated with this polymer and how processing parameters and non-adhesive coatings can improve this. This thesis documents the development of a range of enabling techniques which add to the existing toolbox of nanofabrication technologies. They address a growing demand for nanostructured polymeric surfaces in cell and tissue engineering research, whilst remaining open and adaptable to any application that requires the high throughput production of nanopatterned polymeric samples.
Strategies for High Quality Injection Moulding of Polymer Nanopillars
Macromolecular Materials and Engineering, 2014
Injection moulding is a proven technology for high-throughput production of nanostructures, but high quality replication of pillar-type structures is a considerable challenge, due to the complexities of cavity filling at the timescales involved. We have developed a platform to systematically study the effects of nanostructures with aspect ratios up to 1.2:1 on the quality of moulding, and also considered options for polymer and tooling material. A master template containing nanostructures with a continuous variation in height is produced by a novel fabrication approach using a plasma polymerized hexane layer, deposited with a gradient in thickness, as a sacrificial etch mask. Injection moulding results show that process parameters (tooling temperature and cooling time), material (polystyrene and polycarbonate) as well as a tool surface coating can control the stretching of nanopillar replica dimensions, allowing a variety of final pattern heights using a single master. EPSRC Doctoral Training Allowance scholarship. Mr Paul Reynolds is acknowledged for useful discussions and assistance with injection moulding and Prof. Morgan Alexander at Nottingham University for discussions relating to plasma polymerisation.
IMPRESS targets the development of a technological injection moulding platform for serial production of plastic components incorporating micro or nano scale functional features. The platform is based on most advanced facilities divided in three modules: -tool manufacturing, involving different technologies of micro-nano direct manufacturing, from top-down to bottom-up such as self-assembling, -injection moulding, including equipments fitted with innovative hardware technologies to improve replication quality and capability, -intelligence, dedicated to advanced process control and online metrology integration.
Shape deposition manufacturing of biologically inspired hierarchical microstructures
Cirp Annals-manufacturing Technology, 2008
The applications of dry adhesives range from part handling in manufacturing to aids for human and robotic climbing. Nature provides inspiration in the hierarchical structures used by geckos and spiders to attach using Van der Waals forces. Among the challenges faced in creating synthetic dry adhesives are the need to conform to surfaces at length scales from centimeters to tens of nanometers and the need to create arrays of compliant asymmetric structures at the micro-scale. Initial attempts from the literature are reviewed and a new approach based on a hybrid additive/subtractive prototyping technique called shape deposition manufacturing (SDM) is proposed.
Micro-Nanostructured Polymer Surfaces Using Injection Molding: A Review
Materials Today Communications, 2017
Micro injection molding is in great demand due to its efficiency and applicability for industry. Polymer surfaces having micro-nanostructures can be produced using injection molding. However, it is not as straightforward as scaling-up of conventional injection molding. The paper is organized based on three main technical areas: mold inserts, processing parameters, and demolding. An accurate set of processing parameters is required to achieve precise micro injection molding. This review provides a comparative description of the influence of processing parameters on the quality of final parts and the precision of final product dimensions in both thermoplastic polymers and rubber materials. It also highlights the key parameters to attain a high quality micro-nanostructured polymer and addresses the contradictory effects of these parameters on the final result. Moreover, since the produced part should be properly demolded to possess a high quality textured polymer, various demolding techniques are assessed in this review as well.
Direct molding of nanopatterned polymeric films: Resolution and errors
Applied Physics Letters, 2003
The capability of the direct polymer molding method to transfer ordered nanopatterns from a surface-modified silicon template to polymeric materials, such as polystyrene ͑PS͒ and high-impact polystyrene ͑HIPS͒ is investigated by tapping mode atomic force microscopy ͑AFM͒. The lateral resolution of the method for both materials is 54Ϯ1 nm while the vertical resolution is 5Ϯ1 nm and 3Ϯ1 nm, for PS and HIPS, respectively. This difference is explained by considering the different nanomechanical properties of the polymers. In contrast, HIPS surfaces are more resistant to the wear induced by the repetitive ''reading'' of the surface structure with the AFM tip.
Theoretical and experimental study of a novel microfabricated fibrillar structure
2010
Survival of species such as geckos, spiders, flies, and crickets crucially depends on the interaction between hundreds of thousands of hairs or setae on their feet. Recently, many efforts have been made to fabricate adhesive pads inspired by natural biological systems. Fibres developed from nano molding can mimic the hairs of these species' feet and act as a dry adhesive pad.
On the injection molding of nanostructured polymer surfaces
Polymer Engineering and Science, 2006
Well-defined nano-topographies were prepared by electron-beam lithography and electroplated to form nickel-shims. The surface pattern consisted of square pillars repeated equidistantly within the plane of the surface in a perpendicular arrangement. The width and distance between the squares both ranged from 310 to 3100 nm. All the pillars were 220 nm high. The nickel-shim was used as a surface-template during injection molding of polycarbonate. Secondly, a nickel shim, with a surface pattern consisted of a squared sine with a period of 700 nm and amplitude of 450 nm, was mounted on, and it was in good thermal contact with the upper plate in a hot-press. Polycarbonate/polystyrene was melted on the lower plate while the temperature of the shim was kept below the glass transition temperature. The upper plate was lowered until the shim was in contact with the melt. Experiments were carried out with a clean shim and a shim coated with a monolayer of fluorocarbonsilane. As a result of the surface coating, the amplitude of the replicated grating decreased from about 350 nm in polycarbonate and 100 nm in polystyrene to less than 10 nm. The experiments strongly suggest that the possibility to injection mold sub-micrometer surface structures in polymers mainly relates to adhesive energy between polymer and shim. POLYM. ENG. SCI. 46:160–171, 2006. © 2005 Society of Plastics Engineers