New biological identity of inhaled nanoparticles revealed
(ACS Nano, 2017) – Yi ZuoZuo’s study showed that once the inhaled nanoparticles enter the lungs, they are quickly wrapped with a biomolecular corona made of the natural pulmonary surfactant. The entire surface of the lungs is lined with a lipid-protein pulmonary surfactant film which serves an important physiological function of host defense and surface tension reduction. The pulmonary surfactant corona provides the inhaled nanoparticles with a new identity in their subsequent interactions with the biological system, such as their clearance and cellular toxicity.

Nonlinear mechanics of interlocking cantilevers
(ASME Journal of Applied Mechanics, 2017) – Joseph J. BrownMotivated by their recent work in nanostructure design for microfabricated adhesive surfaces, the authors created and tested a mathematical model for interlocking systems, with comparison to finite-element simulation, iterative modeling, and experiment. The paper’s results show a geometric origin for snap-through motion, and that varying the angle of retention tabs can vary the ratio of insertion force to retention force by 50× or more. The authors anticipate that, in addition to providing a basis for further work in large-deflection mechanics, the work in the paper will contribute to design of new part assembly mechanisms for manufacturing and medical materials. Some possible applications include ultrahigh temperature joints, medical adhesives, joining of dissimilar materials, and assembly of complex or flexible parts.

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Low-cost zeta potentiometry
(Advanced Materials, 2017) – Sangwoo ShinShin et al. have invented a prototype for a low-cost measurement device that can simultaneously measure the zeta potential of colloidal particles and solid surfaces. Colloidal particles are microscopic solid particles suspended in fluid, and their behavior is highly influenced by the zeta potential. The invented method allows measurement of the zeta potential at a significantly lower cost than utilizing a current state-of-the-art device, which sells for more than $50,000.

Falling Walls Hawaiʻi
(presentation based on Nature Comm. paper) – Sangwoo ShinSangwoo Shin has won the competition to present at the prestigious Falling Walls Conference in Berlin, Germany, later this year. Shin was one of 10 participants at Hawaiʻi’s inaugural Falling Walls Lab competition, hosted by the UH Mānoa Institute for Astronomy, with his presentation, “Breaking the Walls of Water Treatment.”

Membraneless water filtration using CO2

(Nature Communications, 2017) – Sangwoo ShinShin et al. have demonstrated a technique for using CO2 in a low-cost water treatment system that eliminates the need for costly and complex filters. The system injects CO2 gas into a stream of water as a method of filtering out particles. The gas, which mixes with the water in a system of channels, temporarily changes the water’s chemistry. The chemical changes cause the contaminating particles to move to one side of the channel depending on their electrical charge. By taking advantage of this migration, the researchers are able to split the water stream and filter out suspended particles. The system is low energy, with bottled carbon dioxide as the only moving part (besides the pump responsible for the flow), and has no physical filter or membrane that can clog or require replacement.

Mechanisms of Wing Beat Sound in Flapping Wings of Beetles
(2017 American Physical Society Division of Fluid Dynamics Conference) – John AllenWhile the aerodynamic aspects of insect flight have received recent attention, the mechanisms of sound production by flapping wings is not well understood. Though the harmonic structure of wing beat frequency modulation has been reported with respect to biological implications, few studies have rigorously quantified it with respect directionality, phase coupling and vortex tip scattering. Moreover, the acoustic detection and classification of invasive species is both of practical as well scientific interest. In this study, the acoustics of the tethered flight of the Coconut Rhinoceros Beetle (Oryctes rhinoceros) is investigated with four element microphone array in conjunction with complementary optical sensors and high speed video. The different experimental methods for wing beat determination are compared in both the time and frequency domain. Flow visualization is used to examine the vortex and sound generation due to the torsional mode of the wing rotation. Results are compared with related experimental studies of the Oriental Flower Beetle.

A student-built fixed-wing UAS for simulated search-and-rescue missions

(HKN Bridge, 2017) – variousUnmanned aerial systems (UAS) have become increasingly popular, especially as multidisciplinary projects in the engineering curriculum. This paper describes a student-built UAS that was entered in the 2017 Association for Unmanned Vehicle Systems International (AUVSI) Seafarer Student Unmanned Aerial System (SUAS) Competition, which simulates a search-and-rescue mission. A fixed-wing UAS was selected for its aerial endurance and long-range capabilities, and was equipped with autonomous capabilities, aerial data transfer, and aerial image capture with onboard image processing. The UAS is capable of autonomously navigating to a designated area and conducting a search for alphanumeric targets over the competition’s 370,000-m2 search area. The onboard image processing and computer-vision algorithms can correctly detect and define the alphanumeric targets with 75% accuracy. The UAS is capable of a 30-minute mission, which also includes dropping a water bottle to a simulated lost hiker.