Stamp Design Research Articles

The Use of Shape Memory Polymers for MEMS Assembly

The advantages of utilizing the polymeric shape memory effect for deterministic assembly of microscale objects are explored in this paper. Assembly of building blocks, referred to as inks, by transfer printing is performed using a polymeric stamp with reversible adhesion as a manipulator. The dynamic rigidity control of a shape memory polymer (SMP) stamp afforded by heating or cooling it across its glass transition temperature allows for a dramatic increase in adhesion during ink retrieval. Furthermore, the shape-fixing and recovery property of the SMP material enables substantial freedom in stamp design, such as more complex surface patterning and heterogeneous surface features, to further reduce adhesion during release, not otherwise available. The mechanics of the stamp adhesion, including the effect of the material’s viscoelasticity and dynamic rigidity on performance, is discussed. Example structures, including a micro-motor structure with a movable rotor, are assembled in order to highlight the benefits afforded using the SMP material over existing alternatives. [2015–0026]

Infrared steganography with individual screening shapes applied to postage stamps with security features

Original scientific paper Designing a postage stamp requires positioning of graphic security elements in a limited small format, so the design is made for two states: for the visible spectrum and the infrared spectrum. Individual screening elements are introduced as security elements in the steganography of invisible pictures in the 700 to 1000 nm spectrum. The CMYKIR theory of hiding the infrared message in the picture is extended by mixing process inks with the control of spot twins of the same colour tone in the X0 and X40 states. Two pictures are integrated in the security print; a multicolour picture visible to the naked eye, and another hidden picture visible when illuminated with an IR detecting instrument. The CMYKIR method is joined with the new element’s algorithm used for dispersing of the hidden picture’s (Z picture’s) fringes. This kind of steganography is applied in the design of postage stamps and it is a new way of securing them.

Images that Speak: Delineating Nigeria’s Modernity through the Graphic Configuration of Postage Stamps

Images possess great visual power, because they embody contents which references varying aspects of a person, community or nations existence and history. Ancient civilizations have been constructed by analysing the visual configuration of images to uncover the historic consciousness of the period they where created. Contemporary discourse on the power of images has thus, embraced and emphasised gravity of images as a unique form of communication and medium of research. Postage stamps constitute one of such images with great visual powers; because it’s designs reflect specific country designations. This paper focused on addressing one research question; how can the visual configuration of stamps be interrogated as visual reference to delineate the modernity of a nation? Adopting visual analysis as methodology of enquiry, this paper examined Nigerian postage stamps from the 1850s to this contemporary age to delineate her transmogrification from primitivism to modernity. Findings from this study led to the conclusion that, through analysis of the changes in stamp designs which very often is impelled by social, cultural, religious or political forces, the entirety of a nations development can be reconstructed, as postage stamps offer insights into paradigm shifts because they constitute a form of visual documentation of a nation’s historic transformation. Through postage stamps as adopted in this paper, Nigeria’s transmogrification into a modernity (modern state) is vividly delineated with the changes in designs found to be influenced by colonialism, nationalist activism, decolonization politics and Pan-Africanism. DOI: 10.5901/mjss.2015.v6n4s2p47

Microfabricated Instrumented Composite Stamps for Transfer Printing

Transfer printing is an emerging process that enables micro- and nano-scale heterogeneous materials integration for applications such as flexible displays, biocompatible sensors, stretchable electronics, and others. It transfers prefabricated micro- and nano-scale functional structures, referred to as “ink,” from growth or fabrication donor substrates to functional receiver substrates using a soft polymeric “stamp,” typically made from polydimethylsiloxane (PDMS) with patterned posts for selectively engaging the ink. In high throughput implementations of the process, where several structures or inks are transferred in a single cycle, the ability to detect contact and monitor localized forces at each post during critical events in the printing process allows for the development of a robust and reliable manufacturing process. It also provides a unique vantage point from which to study fundamental issues and phenomena associated with adhesion and delamination of thin films from a variety of substrate materials. In this paper, we present a new composite stamp design consisting of SU-8 cantilevers instrumented with strain gauges, embedded in a thin film of PDMS patterned with posts, and supported by a backing layer. The fabrication of such a stamp, its testing and calibration are discussed. The use of the instrumented stamp in measuring adhesion forces between silicon and PDMS is demonstrated. New modes of programming the print cycle that monitor forces to control the stamp–substrate interaction are also demonstrated. Finally, a classifier-based approach to detecting failed pick-up or release of the ink is developed and demonstrated to work within a transfer printing cycle.

Experimental Platforms and Finite Element Analysis on Hot Stamping Processes

Due to the complexity of hot stamping mechanism, including the coupling of material formability, thermal interaction and metallurgical microstructure, it makes the process design more difficult even with the aid of the finite element analysis. In the present study, the experimental platforms were developed to measure and derive the friction and heat transfer coefficients, respectively. The experiments at various elevated temperatures and contact pressures were conducted and the friction coefficients and heat transfer coefficients were obtained. A finite element model was also established with the experimental data and the material properties of the boron steel calculated from the JMatPro software. The finite element simulations for the hot stamping forming of an automotive door beam, including transportation analysis, hot forming analysis and die quenching analysis were then performed to examine the forming properties of the door beam. The validation of the finite element results by the production part confirms the efficiency and accuracy of the developed experimental platforms and the finite element analysis for the process design of hot stamping.

The Use of Shape Memory Polymers for Microassembly by Transfer Printing

The advantages of utilizing the polymeric shape memory effect for deterministic assembly of microscale objects are explored in this letter. The assembly is performed by transfer printing, which involves a polymeric stamp with reversible adhesion as a manipulator. The dynamic rigidity control afforded by heating or cooling a shape memory polymer (SMP) stamp across its glass transition temperature allows for a dramatic increase in adhesion during pick-up. Furthermore, the shape-fixing and recovery property of the SMP material enables substantial freedom in stamp design, such as more complex surface patterning and heterogeneous surface features to further reduce adhesion during release not otherwise available.

Stamp design towards instability-induced 3D patterning

Instability-induced pattern formation is easily realized during thermal nanoimprint when a temperature difference is provided between stamp and substrate. The use of this effect for pattern definition requires spacers between stamp and substrate to install a gap of definite height. We test the use of silica particles to serve as spacers with variable height for such an approach. Then, there is no need to prepare stamps with a specific design especially for this purpose, as any stamp available can be used. It turns out that the silica particles are not ideally suited to serve as reliable spacers – they are too soft, when Si stamps are used, but too hard when replica stamps made from OrmoStamp are used. The experiments allow to roughly estimate the mechanical properties of the particles. Nonetheless, it is demonstrated that a formation of isolated polymeric bridges of 5μm in height is feasible.

Phase transformation-based finite element modeling to predict strength and deformation of press-hardened tubular automotive part

In this paper, a new tool design for hot stamping taking advantage of both direct quenching and indirect die quenching is proposed to fabricate the coupled torsion beam axle which is formed from the original tubular-shaped part. This newly proposed hot stamping applies spray of the water before the upper die gets into contact with the tubular part, which significantly enhances the cooling capacity. For other region that cannot be covered by the direct spray, the conventional die quenching method in direct hot stamping process is used. Moreover, for the analysis of the deformation behavior during the proposed hot stamping process, the finite element analysis, which takes the deformation and strengthening induced by the cooling and phase transformation into account, has been carried out. From the analysis, the larger shape change when the cooling time is shorter than 15 s could be explained by the incomplete martensitic phase transformation and phase transformation plastic strain. When the cooling time is short the residual stress after cooling is much higher than those for the longer cooling times.

Stamp Modeling, Analysis and Design of Defected Microstrip Structure for Lowpass Filters Based on Properties of Metamaterials

Defected microstrip structure (DMS) is one kind of metamaterials, which has many characteristics that bandgap and slow wave characteristic and so on. Three types of defected microstrip structure (DMS) units which are cross-shaped, round-head-shaped and square-head-shaped DMS are proposed and investigated. Further, three DMS units are used in the design of lowpass filters (LPFs) and the obtained performances are examined. Based on three DMS units, three lowpass filters using sixteen cascaded proposed DMS units are designed and fabricated. The designed LPFs exhibit sharp cutoff frequency response, low insertion loss, and excellent stopband performance.

Forming Limits of a Sheet Metal After Continuous-Bending-Under-Tension Loading

Forming limit diagrams (FLD) have been widely used as a powerful tool for predicting sheet metal forming failure in the industry. The common assumption for forming limits is that the deformation is limited to in-plane loading and through-thickness bending effects are negligible. In practical sheet metal applications, however, a sheet metal blank normally undergoes a combination of stretching, bending, and unbending, so the deformation is invariably three-dimensional. To understand the localized necking phenomenon under this condition, a new extended Marciniak–Kuczynski (M–K) model is proposed in this paper, which combines the FLD theoretical model with finite element analysis to predict the forming limits after a sheet metal undergoes under continuous-bending-under-tension (CBT) loading. In this hybrid approach, a finite element model is constructed to simulate the CBT process. The deformation variables after the sheet metal reaches steady state are then extracted from the simulation. They are carried over as the initial condition of the extended M–K analysis for forming limit predictions. The obtained results from proposed model are compared with experimental data from Yoshida et al. (2005, “Fracture Limits of Sheet Metals Under Stretch Bending,” Int. J. Mech. Sci., 47(12), pp. 1885–1986) under plane strain deformation mode and the Hutchinson and Neale's (1978(a), “Sheet Necking—II: Time-Independent Behavior,” Mech. Sheet Metal Forming, pp. 127–150) M–K model under in-plane deformation assumption. Several cases are studied, and the results under the CBT loading condition show that the forming limits of post-die-entry material largely depends on the strain, stress, and hardening distributions through the thickness direction. Reduced forming limits are observed for small die radius case. Furthermore, the proposed M–K analysis provides a new understanding of the FLD after this complex bending-unbending-stretching loading condition, which also can be used to evaluate the real process design of sheet metal stamping, especially when the ratio of die entry radii to the metal thickness becomes small.

Research on Impeller Blade Style of Stamping and Welding Multistage Centrifugal Pump

Impact of vane curve on hydraulic performance of the DQ100-64-22 stamping pump was researched by CFD simulation and experiments. The research results show that processing fillet at the connecting section of space blade and shafts only generates minor influence on the pump performance，but it can decrease incidence losses of the inlet flow. The cylindrical blade type has great influence on both inner flow field and hydraulic performance of pump in the high flow rate conditions. The research can supply a good support for the vane curve design and manufacture of stamping and welding multistage centrifugal pumps.

Cooling System CAE Analysis and Optimization Design of Hot Stamping for High Strength Steel Sheet

This paper has done CAE analysis of hot stamping, and optimized the water-cooled system which takes the degree of uniform temperature of blank as the objective function of optimization. The aim is to find a method of optimizing hot stamping mold cooling system based on ANSYS Parametric Design Language (APDL) with ANSYS Mechanical/LS-DYNA software and lay the foundation for designing hot stamping mold. And the work mainly consists of three sections, building parametric finite element model, simulating the process of quenching and optimizing the location parameters and radiuses of each coolant duct. Finally, contrast the optimal result with the initial result and get the conclusion, and moreover, point out the future work.

The Investigation of Multi-Stage Sheet Metal Stamping Process for Deep Drawing

Based on empirical analysis and FEA modeling of multi-stage sheet metal stamping, the optimal sheet metal stamping process can be supplied. Concurrently, the effects of process parameters on formability are found by numerical simulation. Taking an example of deep drawing part, the results got from the numerical simulation are compared with experimental results, which proves that finite element analysis (FEA) is effective and accurate in optimizing the process design of multi-stage sheet metal progressive stamping.

Mechanics of reversible adhesion

By pressure-controlled surface contact area, reversible adhesion can be achieved with strengths tunable by 3 orders of magnitude. This capability facilitates robust transfer printing of active materials and devices onto any surface for the development of stretchable and/or curvilinear electronics. The most important parameter in designing the surfaces of stamps for this process is the height of the microtips relief: tall microtips may fail to pick up electronics from their growth substrate, while short ones may fail to print electronics on the receiver substrate. Mechanics models are developed to determine the range of the microtip height for successful transfer printing. Analytical expressions for the minimum and maximum heights are obtained, which are very useful for stamp design.

An investigation of the detrimental impact of trapped air in thermoplastic micro-embossing

In hot micro-embossing, a thermally softened polymer is forced into the cavities of a patterned stamp. If embossing is performed in normal atmospheric surroundings, it is possible for air to become trapped inside the cavities of the stamp, impeding pattern replication. We present a fast simulation technique that captures the impact of trapped air in the micro-embossing process. The technique can predict the extent of stamp cavity filling for any given stamp design and linear viscoelastic polymer properties, under the assumption that air, once trapped inside a cavity, is unable to escape. We find that the smaller the effective stiffness of the softened polymer relative to the surrounding atmospheric pressure, the more severe the impact of trapped air. Moreover, the trapping of air becomes more detrimental as the widths of stamp cavities become a larger proportion of their lateral spacing. The results of embossing experiments with two widely used thermoplastic polymers, Zeonor 1060R and polymethylmethacrylate, agree with simulation results and indicate that there is little permeation of trapped air in these materials during a typical embossing process of up to 15 min duration, carried out at between 5 and 45 °C above their glass-transition temperatures.

RADIOCARBON CHRONOLOGY OF NEOLITHIC AND BRONZE AGE CULTURES IN YAKUTIA

Based on 92 radiocarbon dates (some unpublished) obtained from 30 sites subjected to dendrochronological calibration, previous chronologies of the Late Neolithic and Bronze Age cultures of Yakutia are revised and a new “calendar chronology” proposed. During the Bronze Age, two newly described cultures existed in addition to the Ust-Mil culture: Ulakhan Segelennyakh and Sugunnakh, the latter being a derivative of Ymyiakhtakh. In the 2nd millennium BC, the Ulakhan Segelennyakh culture became distributed throughout southern, southwestern, and southeastern Yakutia. The distinctive feature of this culture is perceived as being its ceramics which are decorated with punched nodes, stamp, and impressed designs. According to radiocarbon dating, the Sugunnakh culture existed in the transpolar regions of Yakutia from the 1st millennium BC at least until the first centuries AD. All the three Bronze Age cultures of Yakutia evidently originated from the Late Neolithic Ymyiakhtakh culture.

3D visualization of mold filling stages in thermal nanoimprint by white light interferometryand atomic force microscopy

A method for continuous 3D visualization of the mold filling at a microscopic level during athermoplastic nanoimprint process was developed. It is based on superposition ofmicrographs of a series of different stages of imprint. It was applied to two common3D microscopies with different resolution limitations. Due to advanced imageprocessing, the animated movie sequence, available as supplementary multimediainformation in the online version of this journal, gives an unprecedented insightinto the complex polymer flow and shows how voids are forming and vanishingduring the imprint process around micropillars. The method has advantages overcurrent real-time methods and can be used as an analytical tool for optimization ofprocesses and improvement of stamp design down to the sub-10 nm nanometer range.

A computationally simple method for simulating the micro-embossing of thermoplastic layers

We demonstrate a highly computationally efficient approach to simulating the embossing of micrometer-scale, feature-rich patterns on to thermoplastic polymeric layers. The method employs a linear viscoelastic model for the embossed layer and computes the distribution of contact pressure between the polymeric layer and a rigid embossing stamp that is consistent with the progression of the polymer deformation. An approximation to the embossed topography of the polymeric layer is thereby generated as a function of the material being embossed, the stamp's design, and the embossing process's temperature, duration and applied load. For a stamp design described with an 800 × 800 matrix of topographical heights, simulation can be completed within 30–100 s using a personal computer with an Intel Pentium 4 processor and 2 GB RAM. Our method is sufficiently fast for it to be employed iteratively for designing a pattern to be embossed or for selecting processing parameters. The viscoelastic properties of three polymeric materials—polymethylmethacrylate, polycarbonate and Zeonor 1060R, a cyclic olefin polymer—have been experimentally calibrated. For a test pattern having features with diameters of 5 µm to 90 µm, simulated and experimental topographies agree with rms errors of less than 2 µm across all processing conditions tested, with absolute topographical heights ranging up to 30 µm.

Microplasma stamps for selective surface modification: design and characterization

Microplasma stamps are based upon the principle of dielectric barrier discharges. They are applied to a new type of area-selective surface modification process at atmospheric pressure. This process integrates the surface treatment and lateral microstructuring within one process step. For this purpose the plasma is ignited in cavities which are formed temporarily by compressing the microplasma stamp and the substrate to be treated. The advantage of the microplasma stamp designs described in this work is the use of polydimethylsiloxane (PDMS) as a dielectric barrier. Because of its flexibility, PDMS enables a good adjustment to varying surfaces and with it ensures completely closed cavities. In this work the design of two different microplasma stamps is presented. Both designs are characterized considering the influence of the aspect ratio on the ignition and breakdown voltage as well as the ignition under varying conditions. All experiments have been carried out at atmospheric pressure with medium frequency excitation (33 kHz). Furthermore the experimental results are verified by simulations using an SIPDP and FEM model.

Design and optimization of dielectric barrier discharge microplasma stamps

Microplasma stamps based upon the principle of dielectric barrier discharges are applied to a new type of area-selective surface modification process at atmospheric pressure. This process integrates the surface treatment and lateral microstructuring within one process step. For this purpose the plasma is ignited in cavities which are formed temporarily by compressing the microplasma stamp and the substrate to be treated. In this work we compare different microplasma stamp designs with the objective of minimizing the ignition voltage to the smallest possible value. Several experiments with regard to the ignition voltage have been conducted, operating in air at atmospheric pressure with medium frequency excitation (33 kHz). They contrast the influence of different types of electrical contacts as well as different electrode types and cavity sizes (diameter 100–500 µm) on the ignition voltage. Furthermore the influence of different substrates to be treated and the compression force have been analysed.