Microtechnology Applications Research Articles

Z-Ala-Ile-OH, a dipeptide building block suitable for the formation of orthorhombic microtubes.

Self-assembling dipeptides have emerged in the last two decades as promising building blocks for the development of novel biomaterials. Among the various classes of dipeptides, aromatic dipeptides and especially diphenylalanine (Phe-Phe), which forms hexagonal nanotubes, have been the most extensively studied. However, aliphatic peptides or mixed aromatic-aliphatic dipeptides seem just as promising, exhibiting various structures ranging from amyloid fibrils to microtubes. Herein we report the single-crystal structure of an aliphatic dipeptide, alanine-isoleucine (Ala-Ile), C17H24N2O5, protected with a benzyloxycarbonyl (Z) group at the N-terminus. The protected dipeptide crystallizes in the orthorhombic space group P212121 and forms hollow microtubes with orthorhombic symmetry upon evaporation on glass surfaces, as shown by field emission scanning electron microscopy (FESEM). These findings provide an increased understanding of the correlation between the single-crystal structure of the peptide building block and its self-assembly mechanism, and expand the library of available building blocks for microtechnological applications.

Design and fabrication of drug‐delivery systems toward adjustable release profiles for personalized treatment

AbstractAdvanced polymeric controlled delivery systems are designed to effectively treat chronic diseases by adjusting the temporal profile of drug release. Most conventional controlled‐release carriers provide a constant and sustained‐release profile of therapeutics for an extended time. Although these systems have improved the patients’ compliance and adherence and have reduced the administration frequency, they cannot be used for optimal treatment of diseases that require variable patterns of drug release in the treatment regimen. These patterns and the specific rhythms of medical conditions determined by both the body's internal biological clock cycles (i.e., circadian rhythm) and each patient's characteristics call for patient‐specific controlled drug‐delivery systems that can provide adjustable drug release profiles. The importance of individualized therapy and the variety of biodegradable polymers with tunable physicochemical properties promote the design and manufacturing of polymeric delivery systems that release therapeutics at controllable rates. In the past two decades, novel biomaterials and fabrication methods have been utilized to improve the traditional drug‐delivery design and manufacturing technologies. This review article provides a critical discussion of emerging polymeric controlled‐release systems and the mechanisms through which they release their therapeutic agents. Advances and challenges in the design and the fabrication processes of polymeric drug‐delivery systems, particularly solid oral dosage forms and implantable microchips, with controllable release profiles of drugs, are reviewed, focusing on the application of microtechnology and 3D printing techniques in their manufacturing.

Constructivism-Based Teaching and Learning in Indonesian Education

In recent years, constructivism has emerged as the dominant paradigm in education and has made a major intellectual impact on pedagogical development in Indonesia, rooted in Piaget’s cognitive development, and in Vygotsky’s sociocultural theory. Applying constructivism in the classroom is basically rooted from Vygotsky’s psychological theory in which knowledge is not transferred from teachers to students but is constructed in the students’ minds. In this case, the focus of knowledge does not come from teacher to students but from how the students can construct by their own selves. Constructivism has also had a positive impact on the development of science in general in Indonesia. The application of global micro-technology and linguistic research to literacy and the development of constructivist learning narratives has been developed as a substantial approach to teaching in Indonesia. Constructivism is the foundation of teachers because this method represents a shift from behaviorism-based education to cognitive theory-based education. In addition, in recent years, language pedagogy has integrated a variety of instructional approaches that underline the centrality and diversity of learners and their active involvement in authentic and meaningful pursuits as individuals and in the community of learners. This study aimed to reveal the roles of constructivism-based teaching and learning in Indonesian education. In this research, Dewey’s theory of constructivism is the main theory used, in which Dewey states that constructivism can build individual and social knowledge. This study applies a case study approach to ensure the validity of the results of the research conducted as proposed by Kothari (2004). The results showed that constructivism is a promising method and has a positive impact on the progress of education in Indonesia because it can improve students’ abilities. This method also builds students’ knowledge to be creative, and is designed according to their needs.
 Keywords: constructivism, teaching and learning, Indonesian education, Vygotsky’s psychological theory

Dynamics analysis of microparticles in inertial microfluidics for biomedical applications

Inertial microfluidics-based devices have recently attracted much interest and attention due to their simple structure, high throughput, fast processing and low cost. They have been utilised in a wide range of applications in microtechnology, especially for sorting and separating microparticles. This novel class of microfluidics-based devices works based on intrinsic forces, which cause microparticles to migrate laterally and locate at their equilibrium positions. In this article, a comprehensive theoretical formulation is presented for the dynamics of ultrasmall particles in microfluidics-based devices. Explicit expressions are presented for various important forces, which act on a microparticle, such as drag, Magnus, Saffman and wall-induced forces. In addition, the drag coefficient, diffusion phenomenon and Peclet number are formulated. Finally, the influences of particle size, as a crucial parameter, on various intrinsic forces including drag, Magnus and Saffman forces as well as the wall-induced force, are investigated. It is found that the drag, wall-induced and Saffman forces have an important role to play in the dynamics of microparticles in inertial microfluidics while the effects of Magnus force and diffusion can be ignored in most applications.

Experimental investigation on micro-fabrication of wearable dry-patching flexible substrate using transparent superhydrophobic polyimide

Recently, flexible/stretchable devices have drawn much attention owing to their various applications and functions, which necessitates the development of flexible dry-patching platforms. Since wet-patching substrates display a short-term adhesive characteristic, we focused on developing a dry-patching platform that will not only be lightweight, transparent, and flexible, but will also maintain its patching performance for a long time without additional treatments. In this study, we investigated the fabrication of a dry-patching substrate using a polyimide superhydrophobic surface with self-cleaning and water-repellent properties. Polyimide substrates are widely used in microelectronics and micro-technology applications owing to their suitable properties (mechanical, thermal, optical, and chemical properties). To fabricate superhydrophobic surfaces, two key features are required: a material having a low surface energy and surface roughness, for this purpose, the polymer casting method used to fabricate cylindrical micropillar structures. Further, we determined the effect of pillar height and pitch on the surface contact angle. We achieved a contact angle of 179° with a minimum contact angle hysteresis of 10° and an imidized film transparency of 88%. Our approach will minimize the use of liquid gel in wearable devices, which causes unfavorable skin interaction, leading to limited application of wearable devices in daily life.

Direct Metal Forming of a Microdome Structure with a Glassy Carbon Mold for Enhanced Boiling Heat Transfer.

The application of microtechnology to traditional mechanical industries is limited owing to the lack of suitable micropatterning technology for durable materials including metal. In this research, a glassy carbon (GC) micromold was applied for the direct metal forming (DMF) of a microstructure on an aluminum (Al) substrate. The GC mold with microdome cavities was prepared by carbonization of a furan precursor, which was replicated from the thermal reflow photoresist master pattern. A microdome array with a diameter of 8.4 μm, a height of ~0.74 μm, and a pitch of 9.9 μm was successfully fabricated on an Al substrate by using DMF at a forming temperature of 645 °C and an applied pressure of 2 MPa. As a practical application of the proposed DMF process, the enhanced boiling heat transfer characteristics of the DMF microdome Al substrate were analyzed. The DMF microdome Al substrate showed 20.4 ± 2.6% higher critical heat flux and 34.1 ± 5.3% higher heat transfer coefficient than those of a bare Al substrate.

A quick method to fabricate large glass micromodel networks

The study of multi-phase fluid flow in microfluidic devices provides an opportunity for researchers to characterize effective factors and mechanisms in microscale. The application of microtechnology in various fields of science and engineering has always raised different technical problems that require further research and developments. This paper aims to address the associated challenges with micromodel studies that employ the chemical (wet) etching method for making glass micromodels. To overcome these challenges, recent advances in chemical etching are modified and combined to decrease the construction time and costs. The general steps in the chemical etching process are masking, etching, and bonding. First, the common masking step [projecting the designed pattern (regular or irregular) on the acid-resistant layer] in this work is simplified by engraving the mirror plates with a CO2 laser. This new technique skips the required facilities for photoresist layer deposition and UV lithography by using direct laser beam machining of pre-coated soda lime glasses (mirror). Moreover, the variety of mirror products and flexible functionality of laser machines make it possible to create larger size models with any desirable flow pattern. Next, the general composition of solution used in the etching step and the operating conditions of thermal bonding step are modified based on recent investigations in literature to enhance the mechanical strength of the micromodel. Finally, the fabricated model with this procedure is applied in a two-phase flow visualization study to examine the practical features under experimental conditions.

Advance in quality assessment of Chinese materia medica using microscopic and morphological methods

Quality evaluation plays a vital role in ensuring safety and effectiveness of Chinese materia medica (CMM). Microscopic and morphological technologies can be used to distinguish CMM's characteristics, such as shape, size, texture, section, and smell, for authenticity and quality control of CMM. The microscopic and morphological applications of novel micro-technology, colorimeter, and texture analyzer for CMM identification are summarized and the future prospect is discussed in this paper. Various styles and complex sources of CMM are systemically reviewed, including cormophyte medicinal materials, fruit and seeds, pollen grain, and spore materials.

Two-Level Finite Difference Methods for Simulating the High-Dimensional Lagging Models of Heat Conduction

ABSTRACTHeat transfer at microscale plays an important role in microtechnology applications. First, this paper is concerned with the numerical solution of a two-dimensional (2D) heat transfer equation at microscale through a second-order alternating direction implicit (ADI) method. By the discrete energy method, it is shown that the ADI solution converges to the exact solution with a convergence order of in L2-norm. Second, the ADI method is generalized to numerically solve the three-dimensional (3D) problem, and provides numerical solutions of order two in both time and space. Finally, numerical results testify the temporal and spatial accuracy of the ADI method.

Design, development and analysis of a haptic-enabled modular flexure-based manipulator

The development of many applications of microtechnology requires flexible new manipulation tools to perform micromanipulation tasks. A modular piezo-actuated translational flexure-based mechanism is investigated as a basis for the construction of bespoke micromanipulators. The design allows individual single degree of freedom (DOF) translational modules to be serially coupled to form manipulators with multiple DOFs. When the resulting system is controlled through a teleoperated haptic control scheme, it enables a human operator to intuitively perform a broad range of micromanipulation tasks. The mechanical design of the modular system and the haptic control architecture is presented in this paper. Computational analysis is conducted to verify the design methodology, and a planar 2-DOF manipulator experimentally studied to validate the modular concept. Utilizing the 2-DOF system, the haptic control scheme is demonstrated to accurately track user motions, and guide task performance.

Highly Accurate Compact Difference Scheme for SPL Heat Conduction Model of General Body

Abstract Heat transport based on SPL model is of vital importance in microtechnological applications. The heat transport equation is different from the traditional heat conduction equation due to the presence of lagging parameter. In this article, the heat transport in the general body based on SPL heat conduction model under Neumann (insulated) boundary condition is solved by high-order compact difference scheme. The solution is obtained by extending the idea of Dai for discretising Neumann (insulated) boundary condition of heat conduction to the SPL heat conduction model and avoid the need of discretising Neumann boundary conditions. The stability of the numerical scheme has been discussed and observed that the present scheme is unconditionally stable. Model is validated for the thin film of silicon and found that SPL model give the satisfactory results in the macro- and microtemporal scales and up to microspatial scale. A numerical example of particular interest has been studied and discussed in details.

Reversed Janus Micro/Nanomotors with Internal Chemical Engine.

Self-motile Janus colloids are important for enabling a wide variety of microtechnology applications as well as for improving our understanding of the mechanisms of motion of artificial micro- and nanoswimmers. We present here micro/nanomotors which possess a reversed Janus structure of an internal catalytic “chemical engine”. The catalytic material (here platinum (Pt)) is embedded within the interior of the mesoporous silica (mSiO2)-based hollow particles and triggers the decomposition of H2O2 when suspended in an aqueous peroxide (H2O2) solution. The pores/gaps at the noncatalytic (Pt) hemisphere allow the exchange of chemical species in solution between the exterior and the interior of the particle. By varying the diameter of the particles, we observed size-dependent motile behavior in the form of enhanced diffusion for 500 nm particles, and self-phoretic motion, toward the nonmetallic part, for 1.5 and 3 μm ones. The direction of motion was rationalized by a theoretical model based on self-phoresis. For the 3 μm particles, a change in the morphology of the porous part is observed, which is accompanied by a change in the mechanism of propulsion via bubble nucleation and ejection as well as a change in the direction of motion.

Microtechnology-based organ systems and whole-body models for drug screening.

After drug administration, the drugs are absorbed, distributed, metabolized, and excreted (ADME). Because ADME processes affect drug efficacy, various in vitro models have been developed based on the ADME processes. Although these models have been widely accepted as a tool for predicting the effects of drugs, the differences between in vivo and in vitro systems result in high attrition rates of drugs during the development process and remain a major limitation. Recent advances in microtechnology enable more accurate mimicking of the in vivo environment, where cellular behavior and physiological responses to drugs are more realistic; this has led to the development of novel in vitro systems, known as "organ-on-a-chip" systems. The development of organ-on-a-chip systems has progressed to include the reproduction of multiple organ interactions, which is an important step towards "body-on-a-chip" systems that will ultimately predict whole-body responses to drugs. In this review, we summarize the application of microtechnology for the development of in vitro systems that accurately mimic in vivo environments and reconstruct multiple organ models.

Microfluidics: an enabling screening technology for enhanced oil recovery (EOR).

Oil production is a critical industrial process that affects the entire world population and any improvements in its efficiency while reducing its environmental impact are of utmost societal importance. The paper reviews recent applications of microfluidics and microtechnology to study processes of oil extraction and recovery. It shows that microfluidic devices can be useful tools in investigation and visualization of such processes used in the oil & gas industry as fluid propagation, flooding, fracturing, emulsification and many others. Critical macro-scale processes that define oil extraction and recovery are controlled by the micro-scale processes based on wetting, adhesion, surface tension, colloids and other concepts of microfluidics. A growing number of research efforts demonstrates that microfluidics is becoming, albeit slowly, an accepted methodology in this area. We propose several areas of development where implementation of microfluidics may bring about deeper understanding and hence better control over the processes of oil recovery based on fluid propagation, droplet generation, wettability control. Studies of processes such as hydraulic fracturing, sand particle propagation in porous networks, high throughput screening of chemicals (for example, emulsifiers and surfactants) in microfluidic devices that simulate oil reservoirs are proposed to improve our understanding of these complicated physico-chemical systems. We also discuss why methods of additive manufacturing (3D printing) should be evaluated for quick prototyping and modification of the three-dimensional structures replicating natural oil-bearing rock formations for studies accessible to a wider audience of researchers.

Features of Microsystems for Cultivation and Characterization of Stem Cells with the Aim of Regenerative Therapy.

Stem cells have infinite potential for regenerative therapy thanks to their advantageous ability which is differentiable to requisite cell types for recovery and self-renewal. The microsystem has been proved to be more helpful to stem cell studies compared to the traditional methods, relying on its advantageous feature of mimicking in vivo cellular environments as well as other profitable features such as minimum sample consumption for analysis and multiprocedures. A wide variety of microsystems were developed for stem cell studies; however, regenerative therapy-targeted applications of microtechnology should be more emphasized and gain more attractions since the regenerative therapy is one of ultimate goals of biologists and bioengineers. In this review, we introduce stem cell researches harnessing well-known microtechniques (microwell, micropattern, and microfluidic channel) in view point of physical principles and how these systems and principles have been implemented appropriately for characterizing stem cells and finding possible regenerative therapies. Biologists may gain information on the principles of microsystems to apply them to find solutions for their current challenges, and engineers may understand limitations of the conventional microsystems and find new chances for further developing practical microsystems. Through the well combination of engineers and biologists, the regenerative therapy-targeted stem cell researches harnessing microtechnology will find better suitable treatments for human disorders.

Tunable Terahertz Plasmonic Perfect Absorber Based on T-Shaped InSb Array

High absorption efficiency is particularly desirable for various microtechnological applications. In this paper, a nearly perfect terahertz absorber for transverse magnetic (TM) polarization based on T-shaped InSb array is proposed and numerically investigated. Incident wave at the Fabry-Perot resonant frequency can be totally absorbed into the narrow grooves between the two adjacent T-shaped InSb arms. The absorption mechanism is theoretically and numerically studied by using the Fabry-Perot model and the finite element method (FEM), respectively. It is found that the proposed absorber has large angle tolerance. Moreover, the absorption peak can be controlled by varying the temperature. Furthermore, a new absorption peak will emerge while breaking the symmetry of the T-shaped InSb array. This tunable and angle-independent THz perfect absorber may find important applications in THz devices such as microbolometers, coherent thermal emitters, solar cells, photo detectors, and sensors.

Editorial (Hot Topic: Current Applications of Micro and Nano Technology in Human Islet Transplantation)

Editorial (Hot Topic: Current Applications of Micro and Nano Technology in Human Islet Transplantation)

Microsystem for Stem Cell-Based Cardiovascular Research

The emergence of microsystem offers a tool to analyze the biophysical and biochemical functions of individual cells for biosensing, disease diagnostics, drug screening, and fundamental research. With the rapid expansion and eager need for stem cell-based regenerative medicine, introducing microsystem to stem cell research allows locating, culturing, and reprogramming stem cells under a highly controlled microenvironment, including geometrical restriction, surface biochemistry, extracellular matrix (ECM) composites, and cell–cell interactions. This review focused on the application of microtechnology in stem cell-based cardiovascular research to discuss the creation of biomimetic cardiac microenvironment and its influence on stem cell cardiomyogenic differentiation and stem cell–cardiomyocyte interaction. This review was divided into four sections: three-dimensional tissue construction, two-dimensional cell alignment, single-cell micropatterning and analysis, and development of advanced microsystem “heart-on-a-chip”.

A local adaptive differential quadrature method for solving multi-dimensional heat transport equation at the microscale

In this article, we employed the local adaptive differential quadrature method to solve multi-dimensional heat transport equation at the microscale. The local adaptive differential quadrature method was employed to tackle the boundary conditions by using both localized interpolation basis functions and exterior grid points. We found that accurate numerical solution can be obtained by using a small number of gird points for boundary treatments. The governing equation of heat transport was employed to describe the thermal behavior of microstructures, which was of vital importance in microtechnology applications. Four examples showed the effectiveness and accuracy of our algorism in providing excellent estimates of unknown temperature from the given data. We found that the proposed scheme is applicable to the heat transport equation at the microscale.

Diamond-like carbon films as piezoresistors in highly sensitive force sensors

Diamond-like carbon (DLC) films have a high potential as piezoresistors in sensors for microtechnology applications. Since it has been reported that some films show very high strain sensitivity, DLC seems well suited for the use in highly sensitive sensors, e.g. force sensors for the nano Newton region. For DLC films produced by PECVD from hydrocarbons, the process parameters influencing the piezoresistive properties were systematically investigated. Therefore, pressure, gas flow, and substrate bias voltage were varied. The influence of the different parameters, especially on the strain sensitivity of the films, is discussed in this paper. An increase in gas flow and pressure leads to an increased gauge factor. Furthermore, higher strain sensitivity is achieved at lower substrate bias voltages. The different process parameters were optimized for the use of DLC films as piezoresistors in highly sensitive force sensors.