Next Issue
Previous Issue

Table of Contents

Micromachines, Volume 9, Issue 3 (March 2018)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Cover Story (view full-size image) Circulating tumor cells (CTCs) are regarded as a strong biomarker which includes clinically [...] Read more.
View options order results:
result details:
Displaying articles 1-47
Export citation of selected articles as:
Open AccessFeature PaperArticle Fabrication of Through via Holes in Ultra-Thin Fused Silica Wafers for Microwave and Millimeter-Wave Applications
Micromachines 2018, 9(3), 138; https://doi.org/10.3390/mi9030138
Received: 14 February 2018 / Revised: 8 March 2018 / Accepted: 16 March 2018 / Published: 20 March 2018
PDF Full-text (1236 KB) | HTML Full-text | XML Full-text
Abstract
Through via holes in fused silica are a key infrastructure element of microwave and millimeter-wave circuits and 3D integration. In this work, etching through via holes in ultra-thin fused silica wafers using deep reactive-ion etching (DRIE) and laser ablation was developed and analyzed.
[...] Read more.
Through via holes in fused silica are a key infrastructure element of microwave and millimeter-wave circuits and 3D integration. In this work, etching through via holes in ultra-thin fused silica wafers using deep reactive-ion etching (DRIE) and laser ablation was developed and analyzed. The experimental setup and process parameters for both methods are presented and compared. For DRIE, three types of mask materials including KMPR 1035 (Nippon Kayaku, Tokyo, Japan) photoresist, amorphous silicon and chromium—with their corresponding optimized processing recipes—were tested, aiming at etching through a 100 μm fused silica wafer. From the experiments, we concluded that using chromium as the masking material is the best choice when using DRIE. However, we found that the laser ablation method with a laser pulse fluence of 2.89 J/cm2 and a pulse overlap of 91% has advantages over DRIE. The laser ablation method has a simpler process complexity, while offering a fair etching result. In particular, the sidewall profile angle is measured to be 75° to the bottom surface of the wafer, which is ideal for the subsequent metallization process. As a demonstration, a two-inch wafer with 624 via holes was processed using both technologies, and the laser ablation method showed better efficiency compared to DRIE. Full article
Figures

Figure 1

Open AccessArticle Topology Optimization of Passive Micromixers Based on Lagrangian Mapping Method
Micromachines 2018, 9(3), 137; https://doi.org/10.3390/mi9030137
Received: 26 January 2018 / Revised: 17 March 2018 / Accepted: 18 March 2018 / Published: 20 March 2018
Cited by 2 | PDF Full-text (4089 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an optimization-based design method of passive micromixers for immiscible fluids, which means that the Peclet number infinitely large. Based on topology optimization method, an optimization model is constructed to find the optimal layout of the passive micromixers. Being different from
[...] Read more.
This paper presents an optimization-based design method of passive micromixers for immiscible fluids, which means that the Peclet number infinitely large. Based on topology optimization method, an optimization model is constructed to find the optimal layout of the passive micromixers. Being different from the topology optimization methods with Eulerian description of the convection-diffusion dynamics, this proposed method considers the extreme case, where the mixing is dominated completely by the convection with negligible diffusion. In this method, the mixing dynamics is modeled by the mapping method, a Lagrangian description that can deal with the case with convection-dominance. Several numerical examples have been presented to demonstrate the validity of the proposed method. Full article
(This article belongs to the Special Issue Passive Micromixers) Printed Edition available
Figures

Figure 1

Open AccessReview Optofluidics Refractometers
Micromachines 2018, 9(3), 136; https://doi.org/10.3390/mi9030136
Received: 31 January 2018 / Revised: 2 March 2018 / Accepted: 16 March 2018 / Published: 20 March 2018
Cited by 1 | PDF Full-text (5243 KB) | HTML Full-text | XML Full-text
Abstract
Refractometry is a classic analytical method in analytical chemistry and biosensing. By integrating advanced micro- and nano-optical systems with well-developed microfluidics technology, optofluidics are shown to be a powerful, smart and universal platform for refractive index sensing applications. This paper reviews recent work
[...] Read more.
Refractometry is a classic analytical method in analytical chemistry and biosensing. By integrating advanced micro- and nano-optical systems with well-developed microfluidics technology, optofluidics are shown to be a powerful, smart and universal platform for refractive index sensing applications. This paper reviews recent work on optofluidic refractometers based on different sensing mechanisms and structures (e.g., photonic crystal/photonic crystal fibers, waveguides, whisper gallery modes and surface plasmon resonance), and traces the performance enhancement due to the synergistic integration of optics and microfluidics. A brief discussion of future trends in optofluidic refractometers, namely volume sensing and resolution enhancement, are also offered. Full article
(This article belongs to the Special Issue Advances in Optofluidics)
Figures

Figure 1

Open AccessArticle Dielectrophoretic Microfluidic Device for in Vitro Fertilization
Micromachines 2018, 9(3), 135; https://doi.org/10.3390/mi9030135
Received: 30 December 2017 / Revised: 14 March 2018 / Accepted: 15 March 2018 / Published: 20 March 2018
PDF Full-text (4484 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this work was to create a microfluidic platform that uses in vitro fertilization (IVF) and avoids unnecessary damage to oocytes due to the dielectrophoretic force manipulation of the sperms and oocytes that occurs in a traditional IVF operation. The device
[...] Read more.
The aim of this work was to create a microfluidic platform that uses in vitro fertilization (IVF) and avoids unnecessary damage to oocytes due to the dielectrophoretic force manipulation of the sperms and oocytes that occurs in a traditional IVF operation. The device from this research can serve also to decrease medium volumes, as well as the cost of cell culture under evaporation, and to prevent unnecessary risk in intracytoplasmic sperm injection (ICSI). To decrease the impact and destruction of the oocyte and the sperm, we adopted a positive dielectrophoretic force to manipulate both the sperms and the oocyte. The mouse oocytes were trapped with a positive dielectrophoretic (p-DEP) force by using Indium Tin Oxide (ITO)-glass electrodes; the ITO-glass electrode chip was fabricated by wet etching the ITO-glass. The polydimethylsiloxane (PDMS) flow-focusing microfluidic device was used to generate microdroplets of micrometer size to contain the zygotes. The volume of the microdroplets was controlled by adjusting the flow rates of both inlets for oil and the DEP buffer. As a result, the rate of fertilization was increased by about 5% beyond that of the DEP treatment in traditional IVF, and more than 20% developed to the blastocyst stage with a low sperm-oocyte ratio. Full article
Figures

Figure 1

Open AccessArticle Modeling and Analysis of an Opto-Fluidic Sensor for Lab-on-a-Chip Applications
Micromachines 2018, 9(3), 134; https://doi.org/10.3390/mi9030134
Received: 27 February 2018 / Revised: 15 March 2018 / Accepted: 15 March 2018 / Published: 19 March 2018
PDF Full-text (3314 KB) | HTML Full-text | XML Full-text
Abstract
In this work modeling and analysis of an integrated opto-fluidic sensor, with a focus on achievement of single mode optical confinement and continuous flow of microparticles in the microfluidic channel for lab-on-a-chip (LOC) sensing application is presented. This sensor consists of integrated optical
[...] Read more.
In this work modeling and analysis of an integrated opto-fluidic sensor, with a focus on achievement of single mode optical confinement and continuous flow of microparticles in the microfluidic channel for lab-on-a-chip (LOC) sensing application is presented. This sensor consists of integrated optical waveguides, microfluidic channel among other integrated optical components. A continuous flow of microparticles in a narrow fluidic channel is achieved by maintaining the two sealed chambers at different temperatures and by maintaining a constant pressure of 1 Pa at the centroid of narrow fluidic channel geometry. The analysis of silicon on insulator (SOI) integrated optical waveguide at an infrared wavelength of 1550 nm for single mode sensing operation is presented. The optical loss is found to be 5.7 × 10−4 dB/cm with an effective index of 2.3. The model presented in this work can be effectively used to detect the nature of microparticles and continuous monitoring of pathological parameters for sensing applications. Full article
Figures

Figure 1

Open AccessArticle Fabrication and Study of Micro Monolithic Tungsten Ball Tips for Micro/Nano-CMM Probes
Micromachines 2018, 9(3), 133; https://doi.org/10.3390/mi9030133
Received: 2 February 2018 / Revised: 12 March 2018 / Accepted: 13 March 2018 / Published: 19 March 2018
PDF Full-text (3153 KB) | HTML Full-text | XML Full-text
Abstract
Micro ball tips with high precision, small diameter, and high stiffness stems are required to measure microstructures with high aspect ratio. Existing ball tips cannot meet such demands because of their weak qualities. This study used an arc-discharge melting method to fabricate a
[...] Read more.
Micro ball tips with high precision, small diameter, and high stiffness stems are required to measure microstructures with high aspect ratio. Existing ball tips cannot meet such demands because of their weak qualities. This study used an arc-discharge melting method to fabricate a micro monolithic tungsten ball tip on a tungsten stylus. The principles of arc discharge and surface tension phenomenon were introduced. The experimental setup was designed and established. Appropriate process parameters, such as impulse voltage, electro discharge time, and discharge gap were determined. Experimental results showed that a ball tip of approximately 60 µm in diameter with less than 0.6 µm roundness error and 0.6 µm center offset could be realized on a 100 µm-diameter tungsten wire. The fabricated micro ball tip was installed on a homemade probe, touched by high-precision gauge blocks in different directions. A repeatability of 41 nm (K = 2) was obtained. Several interesting phenomena in the ball-forming process were also discussed. The proposed method could be used to fabricate a monolithic probe ball tip, which is necessary for measuring microstructures. Full article
Figures

Figure 1

Open AccessArticle Single-Wall Carbon Nanotube-Coated Cotton Yarn for Electrocardiography Transmission
Micromachines 2018, 9(3), 132; https://doi.org/10.3390/mi9030132
Received: 21 July 2017 / Revised: 1 March 2018 / Accepted: 14 March 2018 / Published: 19 March 2018
PDF Full-text (4891 KB) | HTML Full-text | XML Full-text
Abstract
We fabricated a type of conductive fabric, specifically single-wall carbon nanotube-coated cotton yarns (SWNT-CYs), for electrocardiography (ECG) signal transmission utilizing a “dipping and drying” method. The conductive cotton yarns were prepared by dipping cotton yarns in SWNTs (single-wall carbon nanotubes) solutions and then
[...] Read more.
We fabricated a type of conductive fabric, specifically single-wall carbon nanotube-coated cotton yarns (SWNT-CYs), for electrocardiography (ECG) signal transmission utilizing a “dipping and drying” method. The conductive cotton yarns were prepared by dipping cotton yarns in SWNTs (single-wall carbon nanotubes) solutions and then drying them at room temperature—a simple process that shows consistency in successfully coating cotton yarns with conductive carbon nanotubes (CNTs). The influence of fabrication conditions on the conductivity properties of SWNT-CYs was investigated. The results demonstrate that our conductive yarns can transmit weak bio-electrical (i.e., ECG) signals without significant attenuation and distortion. Our conductive cotton yarns, which combine the flexibility of conventional fabrics and the good conductivity of SWNTs, are promising materials for wearable electronics and sensor applications in the future. Full article
(This article belongs to the Special Issue Carbon Based Materials for MEMS/NEMS)
Figures

Figure 1

Open AccessArticle Silicon-Based Microfabrication of Free-Floating Neural Probes and Insertion Tool for Chronic Applications
Micromachines 2018, 9(3), 131; https://doi.org/10.3390/mi9030131
Received: 8 January 2018 / Revised: 6 March 2018 / Accepted: 14 March 2018 / Published: 16 March 2018
PDF Full-text (3095 KB) | HTML Full-text | XML Full-text
Abstract
Bidirectional neural interfaces for multi-channel, high-density recording and electrical stimulation of neural activity in the central nervous system are fundamental tools for neuroscience and medical applications. Especially for clinical use, these electrical interfaces must be stable over several years, which is still a
[...] Read more.
Bidirectional neural interfaces for multi-channel, high-density recording and electrical stimulation of neural activity in the central nervous system are fundamental tools for neuroscience and medical applications. Especially for clinical use, these electrical interfaces must be stable over several years, which is still a major challenge due to the foreign body response of neural tissue. A feasible solution to reduce this inflammatory response is to enable a free-floating implantation of high-density, silicon-based neural probes to avoid mechanical coupling between the skull and the cortex during brain micromotion. This paper presents our latest development of a reproducible microfabrication process, which allows a monolithic integration of a highly-flexible, polyimide-based cable with a silicon-stiffened neural probe at a high resolution of 1 µm. For a precise and complete insertion of the free-floating probes into the cortex, a new silicon-based, vacuum-actuated insertion tool is presented, which can be attached to commercially available electrode drives. To reduce the electrode impedance and enable safe and stable microstimulation an additional coating with the electrical conductive polymer PEDOT:PSS is used. The long-term stability of the presented free-floating neural probes is demonstrated in vitro and in vivo. The promising results suggest the feasibility of these neural probes for chronic applications. Full article
(This article belongs to the Special Issue Silicon-based Micro/Nanofabrication for Biomedical Applications)
Figures

Figure 1

Open AccessArticle Crack-Configuration Analysis of Metal Conductive Track Embedded in Stretchable Elastomer
Micromachines 2018, 9(3), 130; https://doi.org/10.3390/mi9030130
Received: 28 February 2018 / Revised: 9 March 2018 / Accepted: 9 March 2018 / Published: 15 March 2018
PDF Full-text (17887 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports the analysis of the crack configuration of a stretched metal conductive track that is embedded in a stretchable elastomer. The factor determining the crack configurations is analyzed by modeling as well as experiments. The modeling analysis indicates that the crack
[...] Read more.
This paper reports the analysis of the crack configuration of a stretched metal conductive track that is embedded in a stretchable elastomer. The factor determining the crack configurations is analyzed by modeling as well as experiments. The modeling analysis indicates that the crack configuration is determined by the ratio of the elongation stiffness of the track and elastomer, and is classified into two types: multiple-crack growth and single-crack growth. When the track stiffness is considerably lower than the elastomer stiffness, multiple-crack growth type occurs; in the opposite case, single-crack growth type occurs. Hence, to verify the modeling analysis, metal conductive tracks with different thicknesses are fabricated, and the cracks are studied with respect to the crack width, number of cracks, and crack propagation speed. In this study, two conventional metal-track shapes are studied: straight-shaped tracks with track thickness of 0.04–1.17 µm, and wave-shaped tracks with track thickness of 2–10 µm. For straight-shaped tracks, multiple-crack growth type occurred, when the track thickness was 0.04 µm, and the crack configuration gradually changed to a single crack, with the increase in the track thickness. For wave-shaped tracks with track thickness of 2–10 µm, only single-crack growth type occurred; however, the crack propagation speed decreased and the maximum stretchability of the track increased, with the increase in the track thickness. Full article
Figures

Figure 1

Open AccessArticle A Label Free Disposable Device for Rapid Isolation of Rare Tumor Cells from Blood by Ultrasounds
Micromachines 2018, 9(3), 129; https://doi.org/10.3390/mi9030129
Received: 7 February 2018 / Revised: 4 March 2018 / Accepted: 12 March 2018 / Published: 15 March 2018
PDF Full-text (2765 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The use of blood samples as liquid biopsy is a label-free method for cancer diagnosis that offers benefits over traditional invasive biopsy techniques. Cell sorting by acoustic waves offers a means to separate rare cells from blood samples based on their physical properties
[...] Read more.
The use of blood samples as liquid biopsy is a label-free method for cancer diagnosis that offers benefits over traditional invasive biopsy techniques. Cell sorting by acoustic waves offers a means to separate rare cells from blood samples based on their physical properties in a label-free, contactless and biocompatible manner. Herein, we describe a flow-through separation approach that provides an efficient separation of tumor cells (TCs) from white blood cells (WBCs) in a microfluidic device, “THINUS-Chip” (Thin-Ultrasonic-Separator-Chip), actuated by ultrasounds. We introduce for the first time the concept of plate acoustic waves (PAW) applied to acoustophoresis as a new strategy. It lies in the geometrical chip design: different to other microseparators based on either bulk acoustic waves (BAW) or surface waves (SAW, SSAW and tSAW), it allows the use of polymeric materials without restrictions in the frequency of work. We demonstrate its ability to perform high-throughput isolation of TCs from WBCs, allowing a recovery rate of 84% ± 8% of TCs with a purity higher than 80% and combined viability of 85% at a flow rate of 80 μL/min (4.8 mL/h). The THINUS-Chip performs cell fractionation with low-cost manufacturing processes, opening the door to possible easy printing fabrication. Full article
(This article belongs to the Special Issue Microfluidics for Circulating Biomarkers)
Figures

Figure 1

Open AccessArticle Method of Measuring the Mismatch of Parasitic Capacitance in MEMS Accelerometer Based on Regulating Electrostatic Stiffness
Micromachines 2018, 9(3), 128; https://doi.org/10.3390/mi9030128
Received: 29 January 2018 / Revised: 25 February 2018 / Accepted: 2 March 2018 / Published: 15 March 2018
PDF Full-text (2082 KB) | HTML Full-text | XML Full-text
Abstract
For the MEMS capacitive accelerometer, parasitic capacitance is a serious problem. Its mismatch will deteriorate the performance of accelerometer. Obtaining the mismatch of the parasitic capacitance precisely is helpful for improving the performance of bias and scale. Currently, the method of measuring the
[...] Read more.
For the MEMS capacitive accelerometer, parasitic capacitance is a serious problem. Its mismatch will deteriorate the performance of accelerometer. Obtaining the mismatch of the parasitic capacitance precisely is helpful for improving the performance of bias and scale. Currently, the method of measuring the mismatch is limited in the direct measuring using the instrument. This traditional method has low accuracy for it would lead in extra parasitic capacitive and have other problems. This paper presents a novel method based on the mechanism of a closed-loop accelerometer. The strongly linear relationship between the output of electric force and the square of pre-load voltage is obtained through theoretical derivation and validated by experiment. Based on this relationship, the mismatch of parasitic capacitance can be obtained precisely through regulating electrostatic stiffness without other equipment. The results can be applied in the design of decreasing the mismatch and electrical adjusting for eliminating the influence of the mismatch. Full article
(This article belongs to the Special Issue MEMS Accelerometers)
Figures

Figure 1

Open AccessArticle Experimental Investigation on Ductile Mode Micro-Milling of ZrO2 Ceramics with Diamond-Coated End Mills
Micromachines 2018, 9(3), 127; https://doi.org/10.3390/mi9030127
Received: 12 February 2018 / Revised: 4 March 2018 / Accepted: 12 March 2018 / Published: 14 March 2018
PDF Full-text (8399 KB) | HTML Full-text | XML Full-text
Abstract
ZrO2 ceramics are currently used in a broad range of industrial applications. However, the machining of post-sintered ZrO2 ceramic is a difficult task, due to its high hardness and brittleness. In this study, micro-milling of ZrO2 with two kinds of
[...] Read more.
ZrO2 ceramics are currently used in a broad range of industrial applications. However, the machining of post-sintered ZrO2 ceramic is a difficult task, due to its high hardness and brittleness. In this study, micro-milling of ZrO2 with two kinds of diamond-coated end mills has been conducted on a Kern MMP 2522 micro-milling center (Kern Microtechnik GmbH, Eschenlohe, Germany). To achieve a ductile mode machining of ZrO2, the feed per tooth and depth of cut was set in the range of a few micrometers. Cutting force and machined surface roughness have been measured by a Kistler MiniDynamometer (Kistler Group, Winterthur, Switzerland) and a Talysurf 120 L profilometer (Taylor Hobson Ltd., Leicester, UK), respectively. Machined surface topography and tool wear have been examined under SEM. Experiment results show that the material can be removed in ductile mode, and mirror quality surface with Ra low as 0.02 μm can be achieved. Curled and smooth chips have been collected and observed. The axial cutting force Fz is always bigger than Fx and Fy, and presents a rising trend with increasing of milling length. Tool wear includes delamination of diamond coating and wear of tungsten carbide substrate. Without the protection of diamond coating, the tungsten carbide substrate was worn out quickly, resulting a change of tool tip geometry. Full article
(This article belongs to the Special Issue Micro-Machining: Challenges and Opportunities)
Figures

Figure 1

Open AccessArticle Micro-UFO (Untethered Floating Object): A Highly Accurate Microrobot Manipulation Technique
Micromachines 2018, 9(3), 126; https://doi.org/10.3390/mi9030126
Received: 2 February 2018 / Revised: 3 March 2018 / Accepted: 12 March 2018 / Published: 14 March 2018
PDF Full-text (7304 KB) | HTML Full-text | XML Full-text
Abstract
A new microrobot manipulation technique with high precision (nano level) positional accuracy to move in a liquid environment with diamagnetic levitation is presented. Untethered manipulation of microrobots by means of externally applied magnetic forces has been emerging as a promising field of research,
[...] Read more.
A new microrobot manipulation technique with high precision (nano level) positional accuracy to move in a liquid environment with diamagnetic levitation is presented. Untethered manipulation of microrobots by means of externally applied magnetic forces has been emerging as a promising field of research, particularly due to its potential for medical and biological applications. The purpose of the presented method is to eliminate friction force between the surface of the substrate and microrobot. In an effort to achieve high accuracy motion, required magnetic force for the levitation of the microrobot was determined by finite element method (FEM) simulations in COMSOL (version 5.3, COMSOL Inc., Stockholm, Sweden) and verified by experimental results. According to position of the lifter magnet, the levitation height of the microrobot in the liquid was found analytically, and compared with the experimental results head-to-head. The stable working range of the microrobot is between 30 µm to 330 µm, and it was confirmed in both simulations and experimental results. It can follow the given trajectory with high accuracy (<1 µm error avg.) at varied speeds and levitation heights. Due to the nano-level positioning accuracy, desired locomotion can be achieved in pre-specified trajectories (sinusoidal or circular). During its locomotion, phase difference between lifter magnet and carrier magnet has been observed, and relation with drag force effect has been discussed. Without using strong electromagnets or bulky permanent magnets, our manipulation approach can move the microrobot in three dimensions in a liquid environment. Full article
(This article belongs to the Special Issue Micro/Nano Robotics, Volume II)
Figures

Figure 1

Open AccessFeature PaperCommunication Digital Manufacturing of Selective Porous Barriers in Microchannels Using Multi-Material Stereolithography
Micromachines 2018, 9(3), 125; https://doi.org/10.3390/mi9030125
Received: 1 February 2018 / Revised: 9 March 2018 / Accepted: 13 March 2018 / Published: 14 March 2018
PDF Full-text (1949 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a sequential stereolithographic co-printing process using two different resins for fabricating porous barriers in microfluidic devices. We 3D-printed microfluidic channels with a resin made of poly(ethylene glycol) diacrylate (MW = 258) (PEG-DA-258), a UV photoinitiator, and a UV sensitizer. The
[...] Read more.
We have developed a sequential stereolithographic co-printing process using two different resins for fabricating porous barriers in microfluidic devices. We 3D-printed microfluidic channels with a resin made of poly(ethylene glycol) diacrylate (MW = 258) (PEG-DA-258), a UV photoinitiator, and a UV sensitizer. The porous barriers were created within the microchannels in a different resin made of either PEG-DA (MW = 575) (PEG-DA-575) or 40% (w/w in water) PEG-DA (MW = 700) (40% PEG-DA-700). We showed selective hydrogen ion diffusion across a 3D-printed PEG-DA-575 porous barrier in a cross-channel diffusion chip by observing color changes in phenol red, a pH indicator. We also demonstrated the diffusion of fluorescein across a 3D-printed 40% PEG-DA-700 porous barrier in a symmetric-channel diffusion chip by measuring fluorescence intensity changes across the porous barrier. Creating microfluidic chips with integrated porous barriers using a semi-automated 3D printing process shortens the design and processing time, avoids assembly and bonding complications, and reduces manufacturing costs compared to micromolding processes. We believe that our digital manufacturing method for fabricating selective porous barriers provides an inexpensive, simple, convenient and reproducible route to molecule delivery in the fields of molecular filtration and cell-based microdevices. Full article
(This article belongs to the Special Issue 3D Printed Microfluidic Devices)
Figures

Figure 1

Open AccessArticle Microstructure Formation of Functional Polymers by Evaporative Self-Assembly under Flexible Geometric Confinement
Micromachines 2018, 9(3), 124; https://doi.org/10.3390/mi9030124
Received: 30 January 2018 / Revised: 2 March 2018 / Accepted: 8 March 2018 / Published: 12 March 2018
PDF Full-text (13384 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Polymer microstructures are widely used in optics, flexible electronics, and so forth. We demonstrate a cost-effective bottom-up manner for patterning polymer microstructures by evaporative self-assembly under a flexible geometric confinement at a high temperature. Two-parallel-plates confinement would become curve-to-flat shape geometric confinement as
[...] Read more.
Polymer microstructures are widely used in optics, flexible electronics, and so forth. We demonstrate a cost-effective bottom-up manner for patterning polymer microstructures by evaporative self-assembly under a flexible geometric confinement at a high temperature. Two-parallel-plates confinement would become curve-to-flat shape geometric confinement as the polydimethylsiloxane (PDMS) cover plate deformed during solvent swelling. We found that a flexible cover plate would be favorable for the formation of gradient microstructures, with various periodicities and widths obtained at varied heights of clearance. After thermal annealing, the edge of the PMMA (Poly-methylmethacrylate) microstructures would become smooth, while the RR-P3HT (regioregular-poly(3-hexylthiophene)) might generate nanocrystals. The morphologies of RR-P3HT structures included thick films, straight lines, hierarchical stripes, incomplete stripes, and regular dots. Finally, a simple field-effect transistor (FET) device was demonstrated with the RR-P3HT micropattern as an active layer. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
Figures

Figure 1

Back to Top