Measurement of fluid flow generated by artificial cilia

We observed and measured the fluid flow that was generated by an artificial cilium. The cilium was composed of superparamagnetic microspheres, in which magnetic dipole moments were induced by an external magnetic field. The interaction between the dipole moments resulted in formation of long chains-cilia, and the same external magnetic field was also used to drive the cilia in a periodic manner. Asymmetric periodic motion of the cilium resulted in generation of fluid flow and net pumping of the surrounding fluid. The flow and pumping performance were closely monitored by introducing small fluorescent tracer particles into the system. By detecting their motion, the fluid flow around an individual cilium was mapped and the flow velocities measured. We confirm that symmetric periodic beating of one cilium results in vortical motion only, whereas asymmetry is required for additional translational motion. We determine the effect of asymmetry on the pumping performance of a cilium, verify the theoretically predicted optimal pumping conditions, and determine the fluid behaviour around a linear array of three neighbouring cilia. In this case, the contributions of neighbouring cilia enhance the maximal flow velocity compared with a single cilium and contribute to a more uniform translational flow above the surface.     

Fluid flow due to collective non-reciprocal motion of symmetrically-beating artificial cilia

Using a magneto-mechanical solid-fluid numerical model for permanently magnetic artificial cilia, we show that the metachronal motion of symmetrically beating cilia establishes a net pressure gradient in the direction of the metachronal wave, which creates a unidirectional flow. The flow generated is characterised as a function of the cilia spacing, the length of the metachronal wave, and a dimensionless parameter that characterises the relative importance of the viscous forces over the elastic forces in the cilia.     

Refillable and magnetically actuated drug delivery system using pear-shaped viscoelastic membrane

We report a refillable and valveless drug delivery device actuated by an external magnetic field for on-demand drug release to treat localized diseases. The device features a pear-shaped viscoelastic magnetic membrane inducing asymmetrical deflection and consecutive touchdown motion to the bottom of the dome-shaped drug reservoir in response to a magnetic field, thus achieving controlled discharge of the drug. Maximum drug release with 18 ± 1.5 μg per actuation was achieved under a 500 mT magnetic flux density, and various controlled drug doses were investigated with the combination of the number of accumulated actuations and the strength of the magnetic field.     

Muscle-fiber array inspired,multiple-mode,pneumatic artificial muscles through planar design and one-step rolling fabrication

Advances in development of artificial muscles have enabled creation of soft robots with biological dexterity and self-adaption in unstructured environments; however, production of scalable artificial muscles with multiple-mode actuations remains elusive. Inspired by muscle-fiber arrays in muscular hydrostats, we present a class of versatile artificial muscles called MAIPAMs (muscle-fiber array inspired pneumatic artificial muscles), capable of multiple-mode actuations (such as parallel elongation-bending-spiraling actuations, 10 parallel bending actuations and cascaded elongation-bending-spiraling actuations). Our MAIPAMs consist of active 3D elastomer-balloon arrays reinforced by a passive elastomer membrane, achieved through a planar design and one-step rolling fabrication approach. We introduce prototypical designs for the MAIPAMs and demonstrate their muscle-mimic structures and versatility, as well as their scalable ability to integrate flexible but non-stretchable layers for contraction and twisting actuation modes and compliant electrodes for self-sensing. We further demonstrate that this class of artificial muscles shows potential for versatile robotic applications, such as carrying a camera for recording videos, gripping or manipulating objects, and climbing a pipe-line.     

Adiabatic flow of hydrogen gas through a rocket nozzle with and without composition change

A procedure is described for determining the characteristics of adiabatic flow through a rocket nozzle with and without composition change. The method of calculation is illustrated for the expansion of pure hydrogen gas from a chamber temperature of 306° K. and a pressure of 20.42 atm. to atmospheric pressure.The study indicates that the exhaust velocity and temperature are highest for flow where complete equilibrium is reached at each temperature with respect to the reaction

$\text{H}{}_2\text{?2H}$

Flow with composition change requires a nozzle exit to nozzle throat area ratio somewhat greater than that determined for adiabatic flow without composition change for the same ratio of chamber pressure to exit pressure.The residence time in a given temperature range is computed as a function of gas temperature for the two types of flow. The results of this calculation may be used to determine the minimum required reaction rates which allow composition changes during flow through the nozzle.     

Development of flow through dielectrophoresis microfluidic chips for biofuel production: Sorting and detection of microalgae with different lipid contents

In this study, a continuous flow dielectrophoresis (DEP) microfluidic chip was fabricated and utilized to sort out the microalgae (C. vulgaris) with different lipid contents. The proposed separation scheme is to allow that the microalgae with different lipid contents experience different negative or no DEP force at the separation electrode pair under the pressure-driven flow. The microalgae that experience stronger negative DEP will be directed to the side channel while those experience less negative or no DEP force will pass through the separation electrode pair to remain in the main channel. It was found that the higher the lipid content inside the microalgae, the higher the crossover frequency. Separation of the microalgae with 13% and 21% lipid contents, and 24% and 30%–35% lipid contents was achieved at the operating frequency 7 MHz, and 10 MHz, respectively. Moreover, separation can be further verified by measurement of the fluorescence intensity of the neutral lipid inside the sorted algal cells.     

Defining the determinants of online impulse buying through a shopping process of integrating perceived risk,expectation-confirmation model,and flow theory issues

Since much online shopping is attributed to online impulse buying, it is important to define this particular shopping process. This process has three important issues, perceived risk for virtual stores as well as e-store design and psychological state for online shopping. This is because consumers are both system users and impulse buyers when shopping on e-stores. E-store design is based on the interaction of customers with e-stores and the expectation-confirmation model supports examination of this issue with a wide familiarity in IT use. Psychological state is emotional responses to the stimulus of products in e-stores and flow theory, with task skill and task challenge as precursors, is suitable for exploring this issue. Grounding on the three issues, this study proposes a new research model with these considerations to thoroughly examine the determinants of online impulse buying. Flow state and customer satisfaction also interact with each other. Empirical research shows an important link for the three defined issues of online impulse buying.