Dielectrophoresis for manipulation of micro/nano particles in microfluidic systems

Dielectrophoretic (DEP) force is exerted when a neutral particle is polarized in a non-uniform electric field, and depends on the dielectric properties of the particle and the suspending medium. The integration of DEP and microfluidic systems offers numerous applications for the separation, trapping, assembling, transportation, and characterization of micro/nano particles. This article reviews the applications of DEP forces in microfluidic systems. It presents the theory of dielectrophoresis, different configurations, and the applications of such systems for particle manipulation and device fabrication.

Testosterone manipulation post-castration does not alter cloacal gland growth differences in male quail selected for divergent plasma corticosterone stress response

Japanese quail selected for reduced (low-stress, LS) rather than exaggerated (high-stress, HS) plasma corticosterone response to brief restraint have consistently shown greater cloacal gland (CG) development, an androgen-dependent trait. In this study, the effects of testosterone implants on levels of plasma testosterone and CG development in castrated LS and HS quail were determined. Stress-line males were castrated and randomly allocated to 1 of 3 testosterone treatments: the empty testosterone (ET), low testosterone (LT), or high testosterone (HT) implant group. Cloacal gland volume was determined at 4 weekly intervals that represented ranges of 1 to 9 d, 8 to 17 d, 15 to 24 d, and 22 to 31 d after castration and testosterone implantation. Levels of plasma testosterone were also assessed at the end of the study. Development of the CG was affected by quail line (LS > HS), testosterone treatment (HT > LT > ET), and time of measurement (1 to 9 d < 8 to 17 d < 15 to 24 d = 22 to 31 d after castration and testosterone implantation). A significant interaction between testosterone treatment and time of measurement on CG volume was also detected (with CG volume generally increasing with time in LT- and HT-treated quail, but not in ET-treated quail). However, even though HT implant treatments induced higher CG development than did LT treatments beyond the first interval of CG volume measurement, and despite the finding of greater CG volumes in LS than HS quail during the last 2 measurement intervals within each of the LT and HT groups, no interaction was observed between testosterone implant dosages and quail stress line on CG volume. Thus, by the end of the study, regardless of testosterone dose, CG volume was consistently greater in LS quail than in their HS counterparts. In addition, although, as expected, the testosterone implant treatment significantly altered levels of plasma testosterone (HT > LT > ET), neither quail line nor its interaction with testosterone treatment affected plasma testosterone. The present findings suggest that the often-observed depressed CG development in the HS line may be independent of testosterone effects

Novel dielectrophoretic platforms for manipulation and separation of particles

This research presents the development of a microfluidic system which takes advantage of dielectrophoresis to manipulate particles. The system utilises curved microelectrodes to create strong dielectrophoretic forces within the microchannel, and exploits a novel operating strategy by patterning carbon nanotubes between the microelectrodes to trap low-conductive particles.

Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome

Background and Aim:  Reduction of short-chain poorly absorbed carbohydrates (FODMAPs) in the diet reduces symptoms of irritable bowel syndrome (IBS). In the present study, we aimed to compare the patterns of breath hydrogen and methane and symptoms produced in response to diets that differed only in FODMAP content.
Methods:  Fifteen healthy subjects and 15 with IBS (Rome III criteria) undertook a single-blind, crossover intervention trial involving consuming provided diets that were either low (9 g/day) or high (50 g/day) in FODMAPs for 2 days. Food and gastrointestinal symptom diaries were kept and breath samples collected hourly over 14 h on day 2 of each diet.
Results:  Higher levels of breath hydrogen were produced over the entire day with the high FODMAP diet for healthy volunteers (181 ± 77 ppm.14 h vs 43 ± 18; mean ± SD P < 0.0001) and patients with IBS (242 ± 79 vs 62 ± 23; P < 0.0001), who had higher levels during each dietary period than the controls (P < 0.05). Breath methane, produced by 10 subjects within each group, was reduced with the high FODMAP intake in healthy subjects (47 ± 29 vs 109 ± 77; P = 0.043), but was not different in patients with IBS (126 ± 153 vs 86 ± 72). Gastrointestinal symptoms and lethargy were significantly induced by the high FODMAP diet in patients with IBS, while only increased flatus production was reported by healthy volunteers.
Conclusions:  Dietary FODMAPs induce prolonged hydrogen production in the intestine that is greater in IBS, influence the amount of methane produced, and induce gastrointestinal and systemic symptoms experienced by patients with IBS. The results offer mechanisms underlying the efficacy of the low FODMAP diet in IBS.

Parasitized snails take the heat : a case of host manipulation?

Infection-induced changes in a host’s thermal physiology can represent (1) a generalized host response to infection, (2) a pathological side-effect of infection, or (3), provided the parasite’s development is temperature-dependent, a subtle case of host manipulation. This study investigates parasite-induced changes in the thermal biology of a first intermediate host infected by two castrating trematodes (genera Maritrema and Philophthalmus) using laboratory experiments and Weld surveys. The heat tolerance and temperatures selected by the snail, Zeacumantus subcarinatus, displayed alterations upon infection that differed between the two trematodes. Upon heating, snails infected by Maritrema sustained activity for longer durations than uninfected snails, followed by a more rapid recovery, and selected higher temperatures in a thermal gradient. These snails were also relatively abundant in high shore localities in the summer only, corresponding with seasonal elevated microhabitat temperatures. By contrast, Philophthalmus infected snails fell rapidly into a coma upon heating and did not display altered thermal preferences. The respective heat tolerance of each trematode corresponded with the thermal responses induced in the snail: Maritrema survived exposure to 40°C, while Philophthalmus was less heat tolerant. Although both trematodes infect the same tissues, Philophthalmus leads to a reduction in the host’s thermal tolerance, a response consistent with a pathological side effect. By contrast, Maritrema induces heat tolerance in the snail and withstood exposure to high heat. As the developmental rate and infectivity of Maritrema increase with temperature up to 25°C, one adaptive explanation for our findings is that Maritrema manipulates the snail’s thermal responses to exploit warm microhabitats.

Data-driven computation of contact dynamics during two-point manipulation of deformable objects

This study represents a preliminary step towards data-driven computation of contact dynamics during manipulation of deformable objects at two points of contact. A modeling approach is proposed that characterizes the individual interaction at both points and the mutual effects of the two interactions on each other via a set of parameters. Both global as well as local coordinate systems are tested for encoding the contact mechanics. Artificial neural networks are trained on simulated data to capture the object behavior. A comparison of test data with the output of the trained system reveals a mean squared error percentage between 1% and 3% for simple interactions.

A haptic platform to enable fingertip grasping and manipulation

Haptic technologies allow human users to haptically interact with virtual environments. Haptics has been employed in many application domains including operator training, virtual exploration and teleoperation. Currently, most commercially available haptic devices focus on a single point of haptic interaction. While single-point haptics have been successfully employed in many applications, they remain limited to particular types of haptic interaction. Multi-point haptic devices are a logical progression and facilitate a far wider range of interactions including object grasping, multi-finger object manipulation and size discrimination. The ability to effectively achieve such interactions offers significant benefits for many applications including virtual training, telesurgery and telemanipulation. In such applications, the ability to use multi-point haptic interactions can provide far more effective user interaction as well improved perception of the virtual environment.

The effect of lumbosacral manipulation on corticospinal and spinal reflex excitability on asymptomatic participants

Objective The aim of the study was to examine the effects of a high-velocity, low-amplitude (HVLA) manipulation to the lumbosacral joint on corticospinal excitability, as measured by motor evoked potentials (MEPs) using transcranial magnetic stimulation, and spinal reflex excitability, as measured by the Hoffman reflex (H-reflex).

Methods In a randomized, controlled, crossover design, 14 asymptomatic volunteers (mean age, 23 ± 5.4 years; 10 men; 4 women) were measured for MEPs and H-reflexes immediately before and after a randomly allocated intervention. The interventions consisted of HVLA applied bilaterally to the lumbosacral joint and a control intervention. Participants returned a week later, and the same procedures were performed using the other intervention. Data for H-reflex and MEP amplitudes were normalized to the M-wave maximum amplitude and analyzed using 2-way analysis of variance with repeated measures.

Results A significant interaction of treatment by time was found for MEP (F1,13 = 4.87, P = .04), and post hoc analyses showed that the MEP/M-wave maximum ratio decreased significantly in the HVLA treatment (P = .02; effect size, 0.68). For H-reflex, there was a significant effect of time (F1,13 = 8.186, P = .01) and treatment and time interaction (F1,13 = 9.05, P = .01), with post hoc analyses showing that H-reflexes were significantly reduced after the HVLA manipulation (P = .004; effect size, 0.94). There were no significant changes in MEP latency or silent period duration.

Conclusion An HVLA manipulation applied to the lumbosacral joint produced a significant decrease in corticospinal and spinal reflex excitability, and no significant change occurred after the control intervention. The changes in H-reflexes were larger than those in MEPs, suggesting a greater degree of inhibition at the level of the spinal cord.

Use of a photographic manipulation tool to assess corneal vascular response

Purpose. Corneal vasculature change in contact lens wearers has been linked to the level of hypoxia within the cornea. To assess the impact a treatment has on limbal vessels, a sensitive method of measurement and quantification is required.

Methods. A group of 21 highly myopic, hydrogel wearers, with preexisting signs of corneal hypoxia, were enrolled into a study where they wore sifilcon A silicone hydrogel lenses (Dk/t = 117), on a daily wear basis for 9 months. At all scheduled visits, photographs were taken of the superior, inferior, temporal, and nasal limbal regions which were then imported into Adobe Photoshop. A red-free filter was applied to enhance the contrast of the blood columns. In each quadrant, the length of the longest visible blood column was measured and the blood columns that penetrated >0.5 mm into the cornea were counted. A control group of 11 non-lens wearers was recruited. Their photographs were taken at the beginning of the study and 9 months later. An independent, masked observer assessed the photographs.

Results. There was a significant decrease in the maximum penetration of the blood column in all quadrants (p < 0.001) from baseline to the 9-month visit (e.g., superior: baseline 0.84 ± 0.39 mm; 9 months 0.63 ± 0.20 mm). There was also significant reduction in the number of visible blood columns longer than 0.5 mm in each quadrant (p < 0.001) from baseline to 9 months in all quadrants (e.g., superior: baseline 14.0 ± 8.2; 9 months 6.5 ± 6.0). The control group showed no change over time for the maximum blood column length (p = 0.638) or the number of columns >0.5 mm (p = 0.341).

Conclusions. A group of highly myopic subjects exhibited reduction in the maximum length and number of blood columns in the cornea when refit with a highly permeable silicone hydrogel material. The use of photography, along with Adobe Photoshop software, provides a reliable way of measuring corneal vascular responses over time.

Magnetic liquid marbles, their manipulation and application in optical probing

Magnetic liquid marbles, an encapsulation of liquid droplet with hydrophobic magnetic particles, show remarkable responsiveness to external magnetic force and great potential to be used as a discrete droplet microfluidic system. In this study, we presented the manipulation of a magnetic liquid marble under an external magnetic field and calculated the maximum frictional force, the magnetic force required for actuating the liquid marbles and the effective surface tension of the magnetic liquid marble, as well as the threshold volume for the transition from quasi-spherical to puddle-like shape. By taking advantage of the unique feature of being opened and closed reversibly, we have proven the encapsulated droplets can be detected optically with a reflection-mode probe. Combining the open-close and optical detection also enables to probe chemical reactions taking place within liquid marbles. These remarkable features offer a simple yet powerful alternative to conventional discrete microfluidic systems and may have wide applications in biomedical and drug discovery. © 2012 The Author(s).

Robotic object grasping in context of human grasping and manipulation

This paper presents experimental and deductive findings that shed new light on grasp force estimation, which improves robot’s chances to grasp and manipulate the object close to optimum conditions on the first attempt, which in turn improves robot’s object manipulation dexterity.
This paper proposes that object slippage detection in the human hand is not detected based purely on microvibrations sensed by the human skin during incipient slippage but also on load sensing at each finger and movement of fingers relative to each other while holding an object.