Journal of Micro and Nano-Manufacturing

Journal Information
ISSN / EISSN : 2166-0468 / 2166-0476
Published by: ASME International (10.1115)
Total articles ≅ 349
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Journal of Micro and Nano-Manufacturing; https://doi.org/10.1115/1.4052327

Abstract:
Titanium and its alloys are considered as difficult to cut material classes, and their processing through the traditional machining methods is a painful task. These materials have an outstanding combination of properties like high specific strength, excellent corrosive resistance, and exceptional bio-compatibility; therefore, they have broad fields of application like aerospace, MEMS, bio-medical, etc. Electrochemical micromachining (ECMM) is a very vital process for the production of micro-domain features in difficult-to-machine materials. The machining issue with ECMM for titanium and their alloys is the passive layer formation, which hinders the dissolution and causes stray removal. To overcome these issues, a hybrid ECMM approach has been proposed by using a diamond abrasive tool combined with ECMM. The present study focuses on the detailed characterization of the passive layer formed using the hybrid approach. Through the use abrasive tool, the abrasive grits scoop the passive layer by the mechanical grinding action, formed in micro-drilling on the Ti6Al4V alloy to expose a new surface for further dissolution. The micro-holes were produced incorporating the abrasive tool and then compared by the holes created using a cylindrical tool (tool without abrasive). The taper and the stray dissolution of the micro-holes were also compared, produced at different applied potentials. The minimum average entry overcut and exit overcut of the hole were obtained as 29 µm and 3 µm, respectively, also a micro-hole with the lowest taper of 2.7°, achieved by the use of the abrasive micro tool.
, Guanxiong Miao, Zhijian Pei,
Journal of Micro and Nano-Manufacturing; https://doi.org/10.1115/1.4052253

Abstract:
Feedstock powders used in binder jetting additive manufacturing include nanopowder, micropowder, and granulated powder. Two important characteristics of the feedstock powders are flowability and sinterability. This paper aims to compare the flowability and sinterability of different feedstock powders. Three powders were compared: nanopowder (with a particle size of ~100 nm), micropowder (with a particle size of 70 µm), and granulated powder (with a granule size of ~70 µm) made from the nanopowder by spray freeze drying. Flowability metrics measured included apparent density, tap density, volumetric flow rate, mass flow rate, Hausner ratio, Carr index, and repose angle. Sinterability metrics employed included sintered bulk density, volumetric shrinkage, and densification ratio. Results show that the granulated powder has a higher flowability than the nanopowder and a higher sinterability than the micropowder. Moreover, different flowability metric values of the granulated powder are either higher or lower than those of the micropowder, indicating these two powers have a comparably high flowability. Similarly, different sinterability metric values of the granulated powder are either higher or lower than those of the nanopowder, indicating these two powders have a comparably high sinterability.
Journal of Micro and Nano-Manufacturing, Volume 9; https://doi.org/10.1115/1.4051456

Abstract:
Microneedle arrays contain needlelike microscopic structures, which facilitate drug or vaccine delivery in a minimally invasive way. However, producing hollow microneedles is currently limited by expensive, time consuming and complex microfabrication techniques. In this paper, a novel method to produce hollow polymer microneedles is presented. This method utilizes a femtosecond laser to create hollow microneedle cavities in a mold insert. This mold insert is used in an injection molding process to replicate polymethyl methacrylate microneedles. The combined effect of the mold temperature, volumetric injection rate, and melt temperature on the replication fidelity was evaluated. It was found that the combination of high injection molding parameters facilitated the replication. Furthermore, the functionality of the manufactured hollow microneedles was successfully tested by injecting a controlled flow of colored water into an agarose matrix. The developed methodology enables the production of low-cost, high-volume microneedle devices, which could be a key asset for large scale vaccination campaigns.
Journal of Micro and Nano-Manufacturing; https://doi.org/10.1115/1.4051770

Abstract:
A microfluidic chip requires micro-channels to be created on a substrate. This paper focuses on the design and development of a precision hot embossing machine for replication of microstructures on a PMMA substrate. Kinematic coupling using three spherical balls in radial v-grooves is used to achieve precise positioning of the mold insert with the base. Flexure based parallel guidance mechanism is used for one DOF motion required for the embossing process. The mechanism allows the motion of the mold normal to the substrate surface. Flexure based kinematic coupling with the thermal center is designed to mitigate thermal stress build-up during heating and cooling of the mold insert. An Arduino-based micro-controller is developed to control the temperature profile during the process. A prototype is fabricated and experiments are performed with an aluminium mold insert on a PMMA substrate. The result shows the feasibility of the concept and the set-up can be used to develop a cost-effective precision hot embossing machine for creating micro-patterns for microfluidic applications.
Journal of Micro and Nano-Manufacturing; https://doi.org/10.1115/1.4051631

Abstract:
Pneumatic micro-extrusion (PME) is a direct-write additive manufacturing process, which has emerged as a robust, high-resolution method for the fabrication of a broad spectrum of biological tissues and organs. PME allows for non-contact multi-material deposition of functional inks for tissue engineering applications. In spite of the advantages and engendered potential applications, the PME process is inherently complex, governed by not only complex physical phenomena, but also material-process interactions. Consequently, investigation of the influence of PME process parameters as well as the underlying physical phenomena behind material transport and deposition in PME would be inevitably a need. The overarching goal of this research work is to fabricate biocompatible, porous bone tissue scaffolds for the treatment of osseous fractures, defects, and diseases. In pursuit of this goal, the objectives of the work are: (i) to investigate the influence of seven consequential scaffold design factors and PME process parameters on the mechanical properties of fabricated bone tissue scaffolds; (ii) to explore the underlying dynamics behind material transport in the PME process, using a 3D computational fluid dynamics (CFD) model. To investigate the effects of the design and process parameters, a series of experiments were designed and conducted. Layer height was identified as the most significant factor in this study. An increase in the layer height led to less overlap between subsequent layers, which allowed for more shrinkage and ultimately a reduction in scaffold diameter. In addition, print speed appeared as an influential factor in this study. An increase in the print speed resulted in a decline in linear mass density and thus in the extent of fusion between subsequent deposited layers. Besides, it was observed that there was a strong correlation between deposition mass and compression modulus. Overall, the results of this study pave the way for future investigation of PME-deposited PCL scaffolds with optimal functional and medical properties for incorporation of stem cells toward the treatment of osseous fractures and defects.
Journal of Micro and Nano-Manufacturing; https://doi.org/10.1115/1.4051581

Abstract:
Core-sheath electrospinning is a rapid microfabrication process for creating multi-layer polymer microfibers. This paper presents a process based on core-sheath electrospinning to fabricate poly(L-lactic acid) (PLLA) microtubes with nanopores on the tube wall. The morphology of the microtubes mimics human fenestrated capillary vessels. This study investigates the effects of the viscosities of the core and the sheath solutions on the microtube outer diameter and the nanopore size. The core solution shows a dominating influence on the microtube diameter. At the same core solution viscosity level, the microtube diameter is negatively correlated to the core-to-sheath viscosity ratio. The pore size is positively correlated to the microtube diameter. Understanding the effects of solution viscosity on microtube morphology is the prerequisite for process control and microtube product development for future biomedical applications.
Journal of Micro and Nano-Manufacturing; https://doi.org/10.1115/1.4051473

Abstract:
The Plastics Engineering program at the University of Massachusetts Lowell has taught mold design and engineering to undergraduate students for over 60 years. In 2020, the unexpected arrival of the COVID-19 pandemic in March forced the instructors to revisit the class program and objectives. Similar to other academic courses, the class became virtual. This meant redesigning an intensive hands-on manufacturing class into one that could be taught and taken from our home offices while maintaining academic rigor and continuing to meet critical student learning objectives. The timing of the pandemic meant that students, who were completing tooling split designs and starting CNC programming, could not move forward with machining, assembly, and molding. Instead, their projects became virtual learning experiences. This paper provides the analysis and discussion of how new ideas in teaching were implemented to virtually introduce engineering students to the world of plastic manufacturing. The students' work was carried out on plastic part designs of their choice, some of which included thin walls (<2 mm) and micro-scale features (~ 800 ?m) typical of a micro injection molding process.
Journal of Micro and Nano-Manufacturing; https://doi.org/10.1115/1.4051472

Abstract:
Natural nanomechanisms such as capillaries, neurotransmitters, and ion channels play a vital role in the living systems. But the design principles developed by nature through evolution are not well understood and, hence, not applicable to engineered nanomachines. Thus, the design of nanoscale mechanisms with prescribed functions remains a challenge. Here, we present a systematic approach based on established kinematics techniques to designing, analyzing, and controlling manufacturable nanomachines with prescribed mobility and function built from a finite but extendable number of available "molecular primitives." Our framework allows the systematic exploration of the design space of irreducibly simple nanomachines, built with prescribed motion specification by combining available nanocomponents into systems having constrained, and consequently controllable motions. We show that the proposed framework has allowed us to discover and verify a molecule in the form of a seven link, seven revolute (7R) close loop spatial linkage with mobility (degree of freedom) of one. Furthermore, our experiments exhibit the type and range of motion predicted by our simulations. Enhancing such a structure into functional nanomechanisms by exploiting and controlling their motions individually or as part of an ensemble could galvanize development of the multitude of engineering, scientific, medical, and consumer applications that can benefit from engineered nanomachines.
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