Research Papers

J. Micro Nano-Manuf. 2017;5(2):021001-021001-7. doi:10.1115/1.4035391.

Lapping is a key processing step for precision parts, which directly affects machining quality, precision, and efficiency. Due to some drawbacks of free-abrasive lapping such as deep scratches on the lapped surface, lower lapping efficiency for lower lapping speed, severe waste of abrasive, high-processing cost, and so on, conventional fixed-abrasive lapping (CFL) technology was proposed and developed recently. Meanwhile, considering the unique advantages of the ultrasonic-assisted machining during the processing of those hard and brittle materials and the effect of ultrasonic vibration on the self-sharpening characteristic of abrasive pellet, a novel ultrasonic-assisted fixed-abrasive lapping (UAFL) technology is put forward and corresponding lapping device for engineering ceramics cylindrical part is developed in this paper. Meanwhile, UAFL mechanism and characteristics were studied theoretically and experimentally. Research results show that superimposed ultrasonic vibration changes the lapping movement characteristics and material removal mechanism to a certain extent, helping to heighten material removal rate, smoothen the waveform of tangential force, reduce the average tangential force, and improve surface machining quality. UAFL can be regarded as a high efficiency and precision processing technology for engineering ceramics cylindrical part.

Topics: Grinding , Ceramics
Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2017;5(2):021002-021002-11. doi:10.1115/1.4035619.

Oscillating microprobes avoid high stress and the sticking effect during contact between microprobe and measured surface. The full performance and application scope of oscillating microprobes can be explored and utilized once the reliable prediction of the microprobe contact behavior is understood. Here, an improved contact model considering adhesion forces, surface roughness, and viscoelastic damping for oscillating microprobes is presented and it is validated by exemplary measurements utilizing a uniaxially oscillating electrostatic microprobe. These results show that the nondestructive identification of material classes seems to be feasible by evaluating the phase shift between the sinusoidal signals of sensor and actuator, respectively.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2017;5(2):021003-021003-7. doi:10.1115/1.4035807.

This paper presents smart tooling concepts applied to ultraprecision machining, particularly through the development of smart tool holders, two types of smart cutting tools, and a smart spindle for high-speed drilling and precision turning purposes, respectively. The smart cutting tools presented are force-based devices, which allow measuring the cutting force in real-time. By monitoring the cutting force, a suitable sensor feedback signal can be captured, which can then be applied for the smart machining. Furthermore, an overview of recent research projects on smart spindle development is provided, demonstrating that signal feedback is very closely correlated to the drilling through a multilayer composite board. Implementation aspects on the proposed smart cutting tool are also explored in the application of hybrid dissimilar material machining.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2017;5(2):021004-021004-8. doi:10.1115/1.4035953.

The initial microdot and microline patterns were first ink-jet printed onto the surface of polished AISI420 stainless steel mold. This masked mold substrate was nitrided at 693 K for 7.2 ks at 70 Pa by using the high-density plasma nitriding system. The unmasked parts were selectively nitrided to have higher hardness than 1200 HV. This hardness-profiled substrate was mechanically sand-blasted to fabricate the microtextured mold. Microdisk patterned plastic cover-case for cellular phones were injection-molded by using this method for practical demonstration. Both the selective hardening and anisotropic inner nitriding processes were experimentally discussed as a key step in the present processing.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2017;5(2):021005-021005-9. doi:10.1115/1.4035955.

In this paper, polypropylene (PP) filled with different levels of multiwalled carbon nanotubes (MWCNTs) manufactured by injection molding was closed-loop recycled in order to investigate the effect of recycling and reprocessing on its rheological, electrical, and mechanical properties. It was found that the PP/MWCNT composites keep the flow performance after mechanical recycling. Moreover, the stress and strain at break increase after one reprocessing cycle (mechanical recycling and injection molding), whereas no statistically significant changes in electrical conductivity, Young's modulus, and tensile strength of the PP/MWCNT composites filled with 1, 3, and 5 wt.% were observed.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2017;5(2):021006-021006-6. doi:10.1115/1.4036112.

In this work, we demonstrate a novel scalable microscale manufacturing technique that uses structural self-assembly to create controlled ring-shaped periodic perturbations in the form of wrinkles on a polymer fiber concentric to the fiber axis. The wrinkles are generated by stretching a soft polymer fiber made of polydimethylsiloxane (PDMS) to strains ranging from 10% to 200%, followed by an ultraviolet (UV)/ozone exposure to create a hard SiOx film over the soft fiber before releasing the fiber strain. We identified the key variables controlling the wavelength of the microscale wrinkles. Possible applications of the method in optical and other devices are discussed.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2017;5(2):021007-021007-8. doi:10.1115/1.4036037.

Laser-induced chemical solution synthesis has been recently developed as a new generic method to create porous nanostructured materials for complex and miniaturized devices. The material made by this approach is successfully demonstrated for electrochemical catalytic, nanoscale powders, protective coatings, and other applications. One question has therefore been raised: What are the mechanical properties of the porous materials deposited by the laser-induced chemical solution synthesis? This paper has attempted to explore the mechanical properties of such porous nanostructured materials deposited by this new nanomanufacturing method. This process also offers an innovative opportunity to study the strength of a very simple bonding in additive manufacturing. A thin-film of copper nanoparticles is deposited on copper substrates; then, the microstructure of the deposited film is characterized by scanning electron microscope (SEM), and mechanical properties are investigated by a variety of experiments, such as microhardness test, nano-indentation test, bending test, and adhesion test. The mechanical properties of substrates with surface deposition have been shown to have adequate bond strength (>60 g/mm) to allow effective usage in intended applications. Based on the test results, statistical regression and significant tests have also been carried out. A new model for the nano-indentation of the porous coating (film) is proposed. The empirical results have shown that the effect of coating thickness is more prominent on mechanical properties in the case of thick coating deposition.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2017;5(2):021008-021008-8. doi:10.1115/1.4035956.

We report on periodic, homogeneous nanoripples fabricated on stainless steel (SS), copper (Cu), and aluminum (Al) substrates using an ytterbium pulsed femtosecond laser. These structures called laser induced periodic surface structures (LIPSS) are processed at a relatively high-speed and over large areas. This paper investigates the effect of LIPSS on a wettability behavior of SS, Cu, and Al surfaces. It is shown that nanoripples significantly influenced the wettability character of these metals turning them from hydrophilic to hydrophobic behavior.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Micro Nano-Manuf. 2017;5(2):024501-024501-5. doi:10.1115/1.4035954.

A novel hybrid heating method which combines the conventional electric-resistance specimen heating with microcoil heating of specimen ends to achieve uniform heating over the gauge length is presented. Resistive heating of a miniature specimen develops a parabolic temperature profile with lowest temperature at the grip ends because of the heat loss to the gripper. Coil heating at the specimen ends compensates for this heat loss resulting in uniform temperature distribution over the central segment of the specimen. Thermo-electric finite element simulations were carried out to analyze the transient and steady temperature distribution in miniature specimens followed by experimental validation.

Commentary by Dr. Valentin Fuster

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