Deformation of Pyramidal PDMS Stamps During Microcontact Printing

Microcontact printing (MicroCP) is a form of soft lithography that uses the relief patterns on a master polydimethylsiloxane (PDMS) stamp to form patterns of self-assembled monolayers (SAMs) of ink on the surface of a substrate through conformal contact. Pyramidal PDMS stamps have received a lot of attention in the research community in recent years, due to the fact that the use of the pyramidal architecture has multiple advantages over traditional rectangular and cylindrical PDMS stamps. To better understand the dynamic MicroCP process involving pyramidal PDMS stamps, in this paper, numerical studies on frictionless adhesive contact between pyramidal PDMS stamps and transversely isotropic materials are presented. We use a numerical simulation method in which the adhesive interactions are represented by an interaction potential and the surface deformations are coupled by using half-space Green's functions discretized on the surface. It shows that for pyramidal PDMS stamps, the contact area increases significantly with increasing applied load, and thus, this technique is expected to provide a simple, efficient, and low-cost method to create variable two-dimensional arrays of dot chemical patterns for nanotechnology and biotechnology applications. The DMT-type and Johnson–Kendall–Roberts (JKR)-type-to-DMT-type transition regimes have been explored by conducting the simulations using smaller values of Tabor parameters.

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Novel Chemical Approach to Achieve Advanced Soft Lithography by Developing New Stiffer, Photocurable PDMS Stamp Materials

MRS Proceedings ◽

10.1557/proc-820-o6.2 ◽

2004 ◽

Vol 820 ◽

Author(s):

Kyung M. Choi ◽

John A. Rogers

Keyword(s):

Soft Lithography ◽

High Performance ◽

Microcontact Printing ◽

Low Cost ◽

Pdms Stamp ◽

Molecular Modification ◽

Chemical Approach ◽

New Development ◽

Microfabrication Technology ◽

Novel Devices

AbstractRecent advances in microfabrication technology allow us to develop a number of novel devices with high performance. In microfabrication technology, a new development, ‘soft lithography’, is widely used by making stamps, molding, and microcontact-printing due to the low cost and easy processability. The resolution of soft lithography significantly relies on the performance of stamping materials. However, pattern transfers using commercially available PDMS stamp materials often end up with mechanical failures such as collapse or sag due to their low physical stiffness. Additionally, most of those commercial PDMS materials are thermally curable systems, which results in significant thermal deformations. These limitations have motivated us to start this work, which demonstrates a ‘chemical approach’ to overcome those limits by developing new stiff, photocurable PDMS stamp materials with attached designed functionalities. Molecular modification of PDMS materials results in advanced soft lithography, which produces enhanced physical toughness, lower polymerization shrinkage, and photopatterning capability.

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Chemical Force Microscopy

Microscopy and Microanalysis ◽

10.1017/s1431927600013155 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 1253-1254

Author(s):

Charles M. Lieber ◽

Dmitri Vezenov ◽

Aleksandr Noy ◽

Charles Sanders

Keyword(s):

Functional Groups ◽

Adhesive Contact ◽

Adhesion Forces ◽

Friction Forces ◽

Force Microscopy ◽

Chemical Force Microscopy ◽

Water Solvent ◽

Assembled Monolayers ◽

Adhesive Interactions ◽

Chemical Force

Chemical force microscopy (CFM) has been used to measure adhesion and friction forces between probe tips and substrates covalently modified with self-assembled monolayers (SAMs) that terminate in distinct functional groups. Probe tips have been modified with SAMs using a procedure that involves coating commercial Si3N4 cantilever/tip assemblies with a thin layer of polycrystalline Au followed by immersion in a solution of a functionalized thiol. This methodology provides a reproducible means for endowing the probe with different chemical functional groups.A force microscope has been used to characterize the adhesive interactions between probe tips and substrates that have been modified with SAMs which terminate with COOH and CH3 functional groups in ethanol water solvent. Force versus distance curves recorded under ethanol show that the interaction between COOH/COOH > CH3/CH3 > COOH/CH3. The measured adhesive forces were found to agree well with predictions of the Johnson, Kendall, and Roberts (JKR) theory of adhesive contact, and thus show that the observed adhesion forces correlate with the surface free energy

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ALL-ORGANIC FLEXIBLE AND TRANSARENT AMBIPOLAR FETs WITH ORGANIC BULK HETEROJUNCTIONS

MRS Proceedings ◽

10.1557/proc-1029-f09-20 ◽

2007 ◽

Vol 1029 ◽

Author(s):

Piero Cosseddu ◽

Annalisa Bonfiglio ◽

Ingo Salzmann ◽

Jurge P. Rabe ◽

Norbert Koch

Keyword(s):

Buffer Layer ◽

Double Layer ◽

Soft Lithography ◽

Microcontact Printing ◽

Field Effect Transistors ◽

Layer Structure ◽

Low Cost ◽

Semiconductor Layer ◽

Bulk Heterojunctions ◽

Transparent Plastic

AbstractWe report on the realization of flexible and transparent all-organic Ambipolar Field Effect Transistors. The devices were assembled on a flexible plastic foil, i.e. Mylar®, and the contacts were realized with poly(ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and patterned by means of Soft Lithography, MicroContact Printing (μCP). As semiconductor layer we used organic bulk heterojunctions of pentacene/C60 realized either by co-deposition of the two different molecules or by a double layer structure in which pentacene was used as buffer layer at the interface with the gate dielectric. Interestingly, all devices (co-deposited and double layer), measured in air, worked in accumulation mode as ambipolar OFETs, however some interesting differences between the two structures can be pointed out. Supported by Atomic Force Microscopy, we demonstrated that growing C60 on a pre-deposited pentacene buffer layer leads to a clear improvement in the morphology and crystallinity of the deposited film allowing to improve n-type conduction by two orders of magnitude. This work is particularly interesting because on one hand it confirms the importance of the substrate properties for the ordered growth of organic semiconductors, which determines the transport properties of organic materials; moreover, it demonstrates, also for n-type and ambipolar transistors, the possibility of avoiding problems normally associated to metal contacts: the lack of mechanical robustness, flexibility, and the unfeasibility of realizing contacts with low cost techniques like printing or soft lithography. The flexibility and transparency of the final OFET structure and the simple low cost fabrication technique employed pave the way for an economic mass production of large area transparent “Plastic Electronics”.

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Study of parameters affecting microcontact printing of thiols on gold-coated substrate

International Journal of Modern Physics B ◽

10.1142/s0217979220400408 ◽

2019 ◽

Vol 34 (01n03) ◽

pp. 2040040

Author(s):

Swapna A. Jaywant ◽

Khalid Mahmood Arif

Keyword(s):

Molecular Weight ◽

Soft Lithography ◽

Ph Value ◽

Microcontact Printing ◽

Gold Surface ◽

Self Assembled Monolayers ◽

Wide Range ◽

Assembled Monolayers ◽

Time Required ◽

Compound Concentration

Microcontact printing ([Formula: see text]CP) is a type of soft-lithography technique, which is widely used for patterning self-assembled monolayers (SAMs). It is a convenient method to form SAMs of bio/chemical ink onto different surfaces such as polymers, palladium, silver and gold. A wide range of applications of this technology includes micromachining, patterning proteins, cells or DNA in biosensors. However, the application primarily depends on the type of the ink used. Here, we present an experimental study that provides information about the parameters that affect the [Formula: see text]CP process. Two different thiol inks (dithiothreitol (DTT) and glutathione (GSH)) have been used for obtaining SAMs on gold-coated substrates. Our findings suggest that transferring the alkanethiols over the gold surface is extremely dependent upon the molecular weight of thiol compound, concentration of the thiol solution and pH value of the buffer used. Furthermore, higher the molecular weight, concentration and pH value of the ink, lower is the time required for the process of [Formula: see text]CP.

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New Advances in Molding and Printing Processes for Organic/Plastic Electronics Using Chemically Modified Stiff, Photocured Poly (dimethylsiloxane) (PDMS) Elastomers Designed for Nano-Resolution Soft Lithography

MRS Proceedings ◽

10.1557/proc-788-l9.6 ◽

2003 ◽

Vol 788 ◽

Cited By ~ 1

Author(s):

Kyung M. Choi ◽

John A. Rogers

Keyword(s):

Soft Lithography ◽

High Performance ◽

Low Cost ◽

Pattern Transfer ◽

Pdms Stamp ◽

Organic Plastic ◽

Plastic Electronics ◽

Design And Synthesis ◽

Nano Scale ◽

Printing Processes

ABSTRACTThe development of new materials for organic/plastic electronics allows us to fabricate novel devices through unconventional approaches. The ‘soft lithography technique’ has been widely used in replicating and fabricating small features. This technique is a low cost alternative to photolithography by generating structures from masters to substrates, which employ ‘elastomeric materials’, such as highly stretchable silicon elastomer, polydimethylsiloxane (PDMS) to replicate or transfer the original features to a variety of substrates by molding and printing processes. Since the resolution of pattern transfer significantly relies on the performance of polydimethylsiloxane (PDMS) stamp materials, commercial PDMS materials have shown limitations in high fidelity pattern transfer due to their low physical toughness and high thermal expansion coefficients. For those reasons, pattern fabrications using conventional PDMS materials are unable to satisfy our set of diverse demands, especially in the area of nano-scale replication. To achieve high performance in molding and printing, here we introduce a new strategy, design and synthesis of a modified PDMS silicon elastomer that is a stiffer and photocurable element to achieve our specific task of nano-scale resolution soft lithography. We then demonstrated its unique capabilities for the case of nano-features (300 nm wide) with narrow and tall heights (600 nm height) of photoresist, which is one of the most challenging ‘nano-patterning’ tasks in advanced soft lithography, which is often limited in its use at the nano-scale with other commercially available elastomers.

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New Simplified Low Cost Simulation Method for SME Manufacturing System

International Review of Mechanical Engineering (IREME) ◽

10.15866/ireme.v9i2.5765 ◽

2015 ◽

Vol 9 (2) ◽

pp. 206

Author(s):

Tawfik Benabdallah ◽

Nor Nait Sadi ◽

Mustapha Kamel Abdi

Keyword(s):

Manufacturing System ◽

Low Cost ◽

Simulation Method ◽

Cost Simulation

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Attractive forces slow contact formation between deformable bodies underwater

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2104975118 ◽

2021 ◽

Vol 118 (41) ◽

pp. e2104975118

Author(s):

Mengyue Sun ◽

Nityanshu Kumar ◽

Ali Dhinojwala ◽

Hunter King

Keyword(s):

Three Dimensional ◽

Adhesive Contact ◽

Final State ◽

Underwater Adhesion ◽

Frustrated Total Internal Reflection ◽

Solid Deformation ◽

Hydrophilic Surfaces ◽

Deformable Bodies ◽

Adhesive Interactions

Thermodynamics tells us to expect underwater contact between two hydrophobic surfaces to result in stronger adhesion compared to two hydrophilic surfaces. However, the presence of water changes not only energetics but also the dynamic process of reaching a final state, which couples solid deformation and liquid evacuation. These dynamics can create challenges for achieving strong underwater adhesion/friction, which affects diverse fields including soft robotics, biolocomotion, and tire traction. Closer investigation, requiring sufficiently precise resolution of film evacuation while simultaneously controlling surface wettability, has been lacking. We perform high-resolution in situ frustrated total internal reflection imaging to track underwater contact evolution between soft-elastic hemispheres of varying stiffness and smooth–hard surfaces of varying wettability. Surprisingly, we find the exponential rate of water evacuation from hydrophobic–hydrophobic (adhesive) contact is three orders of magnitude lower than that from hydrophobic–hydrophilic (nonadhesive) contact. The trend of decreasing rate with decreasing wettability of glass sharply changes about a point where thermodynamic adhesion crosses zero, suggesting a transition in mode of evacuation, which is illuminated by three-dimensional spatiotemporal height maps. Adhesive contact is characterized by the early localization of sealed puddles, whereas nonadhesive contact remains smooth, with film-wise evacuation from one central puddle. Measurements with a human thumb and alternatively hydrophobic/hydrophilic glass surface demonstrate practical consequences of the same dynamics: adhesive interactions cause instability in valleys and lead to a state of more trapped water and less intimate solid–solid contact. These findings offer interpretation of patterned texture seen in underwater biolocomotive adaptations as well as insight toward technological implementation.

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A Very Low-Cost, Labor-Efficient, and Simple Method to Block Scattered Ultraviolet Light in PDMS Microfluidic Devices by Inserting Aluminum Foil Strips

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4041436 ◽

2018 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Shuo Wang ◽

Peter Shankles ◽

Scott Retterer ◽

Yong Tae Kang ◽

Chang Kyoung Choi

Keyword(s):

Soft Lithography ◽

Uv Light ◽

Low Cost ◽

Microfluidic Devices ◽

Aluminum Foil ◽

Material Synthesis ◽

Simple Method ◽

Micro Particles ◽

Complex Shapes ◽

The Cost

Abstract Opto-microfluidic methods have advantages for manufacturing complex shapes or structures of micro particles/hydrogels. Most of these microfluidic devices are made of polydimethylsiloxane (PDMS) by soft lithography because of its flexibility of designing and manufacturing. However, PDMS scatters ultraviolet (UV) light, which polymerizes the photocrosslinkable materials at undesirable locations and clogs the microfluidic devices. A fluorescent dye has previously been employed to absorb the scattered UV light and shift its wavelength to effectively solve this issue. However, this method is limited due to the cost of the materials (tens of dollars per microchip), the time consumed on synthesizing the fluorescent material and verifying its quality (two to three days). More importantly, significant expertise on material synthesis and characterization is required for users of the opto-microfluidic technique. The cost of preliminary testing on multiple iterations of different microfluidic chip designs would also be excessive. Alternatively, with a delicate microchannel design, we simply inserted aluminum foil strips (AFS) inside the PDMS device to block the scattered UV light. By using this method, the UV light was limited to the exposure region so that the opto-microfluidic device could consistently generate microgels longer than 6 h. This is a nearly cost- and labor-free method to solve this issue.

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Micropipette-Based Microfluidic Device for Monodisperse Microbubbles Generation

Micromachines ◽

10.3390/mi9080387 ◽

2018 ◽

Vol 9 (8) ◽

pp. 387

Author(s):

Carlos Toshiyuki Matsumi ◽

Wilson José da Silva ◽

Fábio Kurt Schneider ◽

Joaquim Miguel Maia ◽

Rigoberto E. M. Morales ◽

...

Keyword(s):

Electric Fields ◽

Microfluidic Device ◽

Soft Lithography ◽

Low Cost ◽

Characteristic Curve ◽

Microfluidic Devices ◽

Average Diameter ◽

Internal Diameter ◽

Medical Diagnostic ◽

Average Size

Microbubbles have various applications including their use as carrier agents for localized delivery of genes and drugs and in medical diagnostic imagery. Various techniques are used for the production of monodisperse microbubbles including the Gyratory, the coaxial electro-hydrodynamic atomization (CEHDA), the sonication methods, and the use of microfluidic devices. Some of these techniques require safety procedures during the application of intense electric fields (e.g., CEHDA) or soft lithography equipment for the production of microfluidic devices. This study presents a hybrid manufacturing process using micropipettes and 3D printing for the construction of a T-Junction microfluidic device resulting in simple and low cost generation of monodisperse microbubbles. In this work, microbubbles with an average size of 16.6 to 57.7 μm and a polydispersity index (PDI) between 0.47% and 1.06% were generated. When the device is used at higher bubble production rate, the average diameter was 42.8 μm with increased PDI of 3.13%. In addition, a second-order polynomial characteristic curve useful to estimate micropipette internal diameter necessary to generate a desired microbubble size is presented and a linear relationship between the ratio of gaseous and liquid phases flows and the ratio of microbubble and micropipette diameters (i.e., Qg/Ql and Db/Dp) was found.

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