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1.
Rev Sci Instrum ; 90(7): 076108, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31370467

RESUMO

A vast majority of syringe pumps operate on stepper motors, which limits their effectiveness for precision fluid delivery using estimation algorithms. Such a system also hampers the ability to ascertain if the infusion or aspiration instruction has been correctly carried out in the event of power interruptions. To address this issue, a linear servo based actuator system is described to provide absolute indications of the plunger position. System performance in terms of linearity and reliability of plunger translation were verified using a camera tracking system with syringe capacities ranging from 3 to 50 ml and at syringe plunger speeds ranging from 1 to 6.6 mm/s when distilled water was used as the medium. In investigations involving more viscous liquids, the system revealed similarly linear characteristics with 50% glycerol-water (v/v), but cyclical stick-slip behavior with Freund's adjuvant.

2.
Microsc Res Tech ; 82(10): 1741-1747, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31295381

RESUMO

In this work a single glycerol-water mixture, determined to be most apt at 30% (wt/vol), was used to immobilize Drosophila samples as well as to create a liquid lens for smartphone magnification viewing. This provides the advantage of being able to observe immobilized insects directly in the field rather than in the laboratory. In order to avoid having bubbles in the liquid lens and immobilizing medium that hinder visibility, an approach was developed where a stable pendant drop is moved in tandem with the dispensing tip by gravity and stopped abruptly so that sufficient momentum is transferred to the drop for its dislodgement. With 30% glycerol-water (wt/vol) mixtures, applying a minimal stroke of 10 mm with longitudinal impact delivered a momentum of 0.1464 N/s that allowed transfer of a preselected liquid volume for the processes.


Assuntos
Drosophila/anatomia & histologia , Entomologia/instrumentação , Entomologia/métodos , Microscopia/instrumentação , Microscopia/métodos , Smartphone , Animais
3.
Adv Mater ; 31(16): e1804434, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30848003

RESUMO

Properly controlling the rheological properties of nanoparticle inks is crucial to their printability. Here, it is reported that colloidal gels containing a dynamic network of graphene oxide (GO) sheets can display unusual rheological properties after high-rate shearing. When mixed with polyaniline nanofiber dispersions, the GO network not only facilitates the gelation process but also serves as an effective energy-transmission network to allow fast structural recovery after the gel is deformed by high-rate shearing. This extraordinary fast recovery phenomenon has made it possible to use the conventional air-brush spray technique to print the gel with high-throughput and high fidelity on nonplanar flexible surfaces. The as-printed micro-supercapacitors exhibit an areal capacitance 4-6 times higher than traditionally spray-printed ones. This work highlights the hidden potential of 2D materials as functional yet highly efficient rheological enhancers to facilitate industrial processing of nanomaterial-based devices.

4.
Mater Sci Eng C Mater Biol Appl ; 96: 599-605, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30606571

RESUMO

Superhydrophobic substrates facilitate low adhesion for biological liquid handling but are hampered by wetting state changes due to condensation. Here, meshed near-superhydrophobic substrates, that are easier to produce than two-tiered architecture substrates, are shown to provide good immunity to wetting state changes while imbuing high positional resistance to roll-off by tilting when tested with 5 and 10 µL volume drops (18° and 13° respectively) of human IgG antibodies in aqueous solution at both room temperature and 4 °C. Pneumatic actuation was applied to elicit horizontal drop movement over the near-SH surface without any fragmentation, wherein higher velocities can be achieved when smaller drops and higher air pressures are used (0.385 m/s at 33 mbar with the 5 µL drop). A non-contact mode of translating a protein drop towards a highly viscous oil-based adjuvant dispensed from a steel tip allowed for both drops to be combined and aspirated back up into the tip such that subsequent repeated cycles of pendant drop formation and upward aspiration allows for effective mixing to achieve a stable emulsion. The findings here advance the development of devices that enable improved antigen-adjuvant preparation by reducing the amount of reagents required and product losses from surface adsorption.


Assuntos
Interações Hidrofóbicas e Hidrofílicas , Imunoglobulina G/química , Emulsões , Humanos
5.
Rev Sci Instrum ; 89(10): 106102, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30399692

RESUMO

The ability to conduct en-route centrifugation of samples improves quality and timeliness in the pre-analytical phase. This is demonstrated here on a quadcopter whereby the propellers were adapted to house and apply centrifugal forces to sample-containing capillary tubes instead of incorporating a centrifuge. Tests revealed the ability of the method to separate non-homogenized milk into a cream portion and a skim milk portion, and human whole blood into plasma, buffy coat, and red blood cell components.

6.
Biochem Mol Biol Educ ; 46(3): 245-252, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29488323

RESUMO

The appreciation and understanding of gas generation through processes is vital in biochemical education. In this work, an augmented reality tool is reported to depict the redox reaction between hydrogen peroxide and sodium hypochlorite solutions, two ubiquitous oxidizing agents, to create oxygen, a combustible gas. As it operates out of smartphones or tablets, students are able to conduct the exercise collaboratively, respond in a manner similar to an actual physical experiment, and able to depict the oxygen volume changes in relation to the volume of hydrogen peroxide of different concentrations used. The tool offers to help students acquire bench skills by limiting handing risks and to mitigate possible student anxiety on handling chemical materials and implements in the laboratory. The feedback received from Year 11 and 12 high school student participants in an outreach exercise indicate the overall effectiveness of this tool. © 2018 by The International Union of Biochemistry and Molecular Biology, 46(3):245-252, 2018.


Assuntos
Peróxido de Hidrogênio/química , Oxigênio/química , Aprendizagem Baseada em Problemas , Hipoclorito de Sódio/química , Estudantes , Compreensão , Humanos , Instituições Acadêmicas
7.
Anal Biochem ; 545: 1-3, 2018 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-29307634

RESUMO

Autonomous systems for sample transport to the laboratory for analysis can be improved in terms of timeliness, cost and error mitigation in the pre-analytical testing phase. Drones have been reported for outdoor sample transport but incorporating devices on them to attain homogenous mixing of reagents during flight to enhance sample processing timeliness is limited by payload issues. It is shown here that flipping maneuvers conducted with quadcopters are able to facilitate complete and gentle mixing. This capability incorporated during automated sample transport serves to address an important factor contributing to pre-analytical variability which ultimately impacts on test result reliability.


Assuntos
Testes Imediatos , Impressão Tridimensional , Biomarcadores/análise , Humanos , Testes Imediatos/economia , Impressão Tridimensional/economia , Impressão Tridimensional/instrumentação
8.
ACS Omega ; 3(8): 9310-9317, 2018 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-31459064

RESUMO

Facile creation of multiple drops at appropriate volumes on surfaces without the use of sophisticated instrumentation facilitates downstream evaporative preconcentration of liquid samples for analytical purposes. In this work, a superhydrophobic (SH) substrate comprising wells with a perforated mesh base was developed for simultaneous drop creation in a quick and convenient manner. In contrast to the method of pouring liquid directly over the SH wells, consistent liquid filling was readily achieved by a simple immersion approach. This method works well even for challenging situations where well diameters are smaller than 3.4 mm. Despite the poor liquid-retention properties of SH surfaces, inverting the wells did not result in liquid detachment under gravitational force, indicating strong pinning effects afforded by the well architecture. The perforated base of the well allowed the liquid to be completely removed from the well by compressed air. High-speed camera image processing was used to study the evolution of drop contact angle and displacement with time. It was found that the liquid body was able to undergo strong oscillations. Optical spectroscopy was used to confirm the ability of evaporative preconcentration of silver nanoparticles.

9.
Langmuir ; 33(48): 13892-13898, 2017 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-29116806

RESUMO

Valves used to control liquid filling and draining processes from storage typically need to be actuated. Here, we show that similar flow enabling and restricting operations can be achieved through millimeter scale holes that function according to the amount of hydrostatic pressure applied without any other intervention. This phenomena is exhibited using receptacles where the base is made of either a hydrophilic or superhydrophobic substrate with hole sizes ranging from 1.0-2.0 mm. The construction is such that the drainage flow velocities are of the same order in both substrates and follow Torricelli's law trends. Nevertheless, the primary mechanisms responsible for resisting the onset of flow in each substrate are different; nonbreaching of the advancing contact angle threshold in the former, and stable maintenance of an elastic-like deformation of the liquid-gas interface that is connected to the surrounding plastron in the latter. These differences are demonstrated using an upward jet of water delivered to the orifice, where a discharging flow from the hydrophilic base occurred before the threshold hydrostatic pressure condition was attained, while liquid from the jet is subsumed into the liquid body of the receptacle with the superhydrophobic base without any leakage. These findings portend advantages in simplicity and robustness for a myriad of liquid-related processes.

10.
ACS Omega ; 2(9): 6211-6222, 2017 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31457866

RESUMO

Drops with larger volumes placed over a superhydrophobic (SH) surface with a hole do not fall through unless they are evaporated to a size that is small enough. This feature offers the ability to preconcentrate samples for biochemical analysis. In this work, the influence of pinning on the behavior of drops placed on a 0.1 mm thick SH substrate with a 2 mm diameter hole as they evaporated was investigated. With 16 µL of water dispensed, the sessile drop component volume was initially higher than that of the overhanging drop component and maintained this until the later stages where almost identical shapes were attained and full evaporation was achieved without falling off the hole. With 15 µL of water dispensed, the volume of the sessile drop was initially higher than that of the overhanging drop component but the liquid body was able to squeeze through the hole after 180 s due to the contact line not having sufficient pinning strength when it encountered the edge of the hole. This resulted in the liquid body either falling through the hole or remaining pinned with an oval-like shape. When it did not fall-off, the liquid body had volume and contact angle characteristics for the sessile drop and overhanging drop components that were reversed. In the later stages, however, nearly identical shapes were again attained and full evaporation was achieved without falling off the hole. The effects of pinning, despite the substrate being SH, offer another path toward achieving practical outcomes with liquid bodies without the need for chemical surface functionalization. Similarities and differences could be seen in the behavior of a sessile drop on a SH plate that was inclined at 30° to the horizontal and evaporated.

11.
Rev Sci Instrum ; 87(11): 115107, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27910552

RESUMO

A method to measure the contact angle, which is indicative of wetting, using small liquid volumes dispensed directly on microplate wells is described and demonstrated. Experiments with enhanced green protein samples of volumes 4.4-6 µl showed no measured variance in the contact angle. Experiments with phosphate buffer solution with varied concentrations of a non-ionic detergent (Tween 20) dissolved, however, revealed smaller contact angles with increased detergent concentration. It is experimentally shown that drops can be located up to 7° from the lowest position of the well without affecting the accuracy of contact angle measurements. Numerical simulations confirm the ability of the drops to manifest the correct contact angle despite the lack of axis-symmetry in their shape while residing on a circular surface. This method offers a convenient means to determine the wetting characteristics of different liquid samples in different microplates.

12.
Langmuir ; 32(33): 8550-6, 2016 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-27479030

RESUMO

In this work, 2 µL water drops are placed on substrates that are created to have a circular hydrophilic region bounded by superhydrophobicity so that they exhibit high contact angles. When the substrate is translated by a linear stepper actuator, the random force components present in the actuator are shown to cause the drop to rock resonantly. When the substrate is translated downward at inclination angles of up to 6° with respect to the horizontal, the contact angle hysteresis increases progressively to a limiting condition. When the substrate is moved up at inclined angles, alternatively, the contact angle hysteresis increases initially to the limiting condition before it is progressively restored to its static state. These behaviors are accounted for by the reversible micro-Cassie to Wenzel wetting state transformations that are made possible by the hierarchical microscale and nanoscale structures present in the superhydrophobic regions.

13.
Anal Biochem ; 506: 28-30, 2016 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-27156813

RESUMO

During the collection phase of the dried blood spot method, practitioners need to ensure that there is no smearing of the blood sample on the filter paper or else readings from it will be invalid. This can be difficult to accomplish in the field if there is relative motion between the site of blood discharge on the finger and the filter paper. In this article, a gyroscope stabilization method is introduced and demonstrated to provide consistent and improved dried blood spot collection within a circular guide region notwithstanding the presence of rocking.


Assuntos
Teste em Amostras de Sangue Seco/instrumentação , Teste em Amostras de Sangue Seco/métodos , Humanos
14.
J Lab Autom ; 21(6): 799-805, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26882923

RESUMO

Flexible automation systems provide the needed adaptability to serve shorter-term projects and specialty applications in biochemical analysis. A low-cost selective compliant articulated robotic arm designed for liquid spillage avoidance is developed here. In the vertical-plane robotic arm movement test, the signals from an inertial measurement unit (IMU) and accelerometer were able to sense collisions. In the horizontal movement test, however, only the signals from the IMU enabled collision to be detected. Using a calculation method developed, it was possible to chart the regions where the obstacle was likely to be located when a collision occurred. The low cost of the IMU and its easy incorporation into the robotic arm offer the potential to meet the pressures of lowering operating costs, apply laboratory automation in resource-limited venues, and obviate human intervention in response to sudden disease outbreaks.


Assuntos
Automação Laboratorial/métodos , Robótica/métodos , Manejo de Espécimes/métodos , Automação Laboratorial/economia , Custos e Análise de Custo , Humanos , Robótica/economia
15.
Eur Phys J E Soft Matter ; 38(11): 119, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26577818

RESUMO

We advance a scheme in which a liquid body on a stationary tip in contact with a rotating superhydrophobic surface is able to maintain resonance primarily from stick-slip events. With tip-to-surface spacing in the range 2.73 ≤ h < 2.45 mm for a volume of 10 µL, the liquid body was found to exhibit resonance independent of the speed of the drum. The mechanics were found to be due to a surface-tension-controlled vibration mode based on the natural frequency values determined. With spacing in the range 2.45 ≤ h < 2.15 mm imposed for a volume of 10 µL, the contact length of the liquid body was found to vary with rotation of the SH drum. This was due to the stick-slip events being able to generate higher energy fluctuations causing the liquid-solid contact areas to vary since the almost oblate spheroid shape of the liquid body had intrinsically higher surface energies. This resulted in the natural frequency perturbations being frequency- and amplitude-modulated over a lower frequency carrier. These findings have positive implications for microfluidic sensing.


Assuntos
Microfluídica , Nanoestruturas/química , Interações Hidrofóbicas e Hidrofílicas , Rotação , Propriedades de Superfície
16.
Soft Matter ; 11(38): 7474-7, 2015 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-26305149

RESUMO

Captive bubbles that reside on superhydrophobic surfaces with plastrons move uncontrollably when tilted. A system based on creating moveable local apexes on flexible superhydrophobic foils is shown to allow controlled transport. Simulations done reveal that specific bubble transport speeds are needed to form concentration gradients suited for aerotaxis study and sensing.


Assuntos
Gases/química , Técnicas Analíticas Microfluídicas/instrumentação , Água/química , Simulação por Computador , Desenho de Equipamento , Interações Hidrofóbicas e Hidrofílicas , Modelos Químicos , Movimento (Física) , Propriedades de Superfície
17.
Environ Toxicol Pharmacol ; 40(1): 187-90, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26141660

RESUMO

There are significant challenges in assessing the toxicity of nanoparticles in the environment in which effective methods for detection are crucial. An inexpensive method that uses superhydrophobic well with an evaporating droplet followed by a simple squeeze flow is described here and found to provide practical high nanoparticle collection from samples for detection. The process could be hastened by placing a radiant heater close to the droplet if temperature rises in the sample can be tolerated.


Assuntos
Monitoramento Ambiental , Nanopartículas
18.
Langmuir ; 31(24): 6695-703, 2015 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-25986160

RESUMO

Captive bubbles on a superhydrophobic (SH) surface have been shown to increase in volume via injection of air through the surrounding plastron. The experimental contact diameter against volume trends were found to follow that predicted by the Surface Evolver simulation generally but corresponded with the simulated data at contact angle (CA) = 158° when the volume was 20 µL but that at CA = 170° when the volume was increased to 180 µL. In this regime, there was a simultaneous outward movement of the contact line as well as a small reduction in the slope that the liquid-air interface makes with the horizontal as air was injected. At volumes higher than 180 µL, air injection caused the diameter to reduce progressively until detachment. The inward movement of the contact line in this regime allowed the bubble body to undergo shape deformations to stay attached onto the substrate with larger volumes (300 µL) than predicted (220 µL at CA = 170°) using simulation. In experiments to investigate the effect of translating the SH surface, movement of captive bubbles was possible with 280 µL volume but not with 80 µL volume. This pointed to the possibility of transporting gas-phase samples on SH surfaces using larger captive bubble volumes.

19.
Opt Lett ; 40(5): 697-700, 2015 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-25723410

RESUMO

Flow-based measures to automate optical trapping have significant limitations. A scheme is advanced here where a spherical bead is first located in a trap, and a second bead below the focus point is selectively drawn into the trap to replace the original particle. Experimentation conducted showed that it was possible to do so with little perturbation of other surrounding particles. Simulations done allowed for a clearer description of the exchange mechanism.

20.
Lab Chip ; 15(4): 991-5, 2015 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-25511936

RESUMO

Superhydrophobic surfaces aid biochemical analysis by limiting sample loss. A system based on wells here tolerated tilting up to 20° and allowed air logic transfer with evidence of mixing. Conditions for intact transfer on 15 to 60 µL drops using compressed air pressure operation were also mapped.


Assuntos
Ar , Técnicas Analíticas Microfluídicas , Pressão do Ar , Interações Hidrofóbicas e Hidrofílicas , Técnicas Analíticas Microfluídicas/instrumentação , Tamanho da Partícula , Propriedades de Superfície , Temperatura Ambiente
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