Sulfonated-polydimethylsiloxane (PDMS) microdevices with enhanced electroosmotic pumping and stability

2006 ◽  
Vol 84 (4) ◽  
pp. 720-729 ◽  
Author(s):  
Bin Wang ◽  
J Hugh Horton ◽  
Richard D Oleschuk
Keyword(s):  
Electroosmotic Flow ◽  
Aging Effect ◽  
Polymer Materials ◽  
Air Plasma ◽  
Aging Effects ◽  
Pdms Surface ◽  
Electroosmotic Pumping ◽  
Modified Surface ◽  
Pdms Chip ◽  
Chemical Force

Polydimethylsiloxane (PDMS) microfluidic devices offer several advantages in terms of cost and ease of fabrication compared with those fabricated from both glass and silicon materials. PDMS, however, has some potential disadvantages compared with other materials including high hydrophobicity, which makes filling the micron-sized channels difficult, and minimal surface charge resulting in reduced electroosmotic flow (EOF). Here, we describe the oxidation of the PDMS surface to form silanol groups using both air plasma and a discharge from a Tesla coil, and subsequent modification to form sulfonated-PDMS surfaces. The flow performance of freshly prepared and aged sulfonated-PDMS chips was determined at pH 5 and compared with those of unmodified and oxidized PDMS chips. The electroosmotic mobility (µeo) for a sulfonated-PDMS microdevice was determined at various pH values (pH 3~8) and compared with that for an oxidized PDMS chip. The lower pKa of a sulfonic acid modified surface compared with a silanol modified surface generated a stronger EOF over the entire pH range studied. Chemical force titrations were used to characterize the changes in functional groups present on the surface of freshly prepared and aged sulfonated-PDMS surfaces. These experiments show that the sulfonated-PDMS is a superior material for use in microfluidic applications because (i) it supports EOF over a much wider range of pH than similar polymer materials and (ii) is less susceptible to degradation of its EOF rate owing to air aging effects and surface reorganization.Key words: polydimethylsiloxane (PDMS), sulfonated surface modification, electroosmotic flow (EOF), aging effect, chemical force titrations.

Aging Effects on Oxidized and Amine-Modified Poly(dimethylsiloxane) Surfaces Studied with Chemical Force Titrations:  Effects on Electroosmotic Flow Rate in Microfluidic Channels

Langmuir ◽  
2003 ◽  
Vol 19 (23) ◽  
pp. 9792-9798 ◽  
Author(s):  
Bin Wang ◽  
Lu Chen ◽  
Zamin Abdulali-Kanji ◽  
J. Hugh Horton ◽  
Richard D. Oleschuk
Keyword(s):  
Flow Rate ◽  
Electroosmotic Flow ◽  
Microfluidic Channels ◽  
Aging Effects ◽  
Chemical Force

scholarly journals Universal Plasma Jet for Droplet Manipulation on a PDMS Surface towards Wall-Less Scaffolds

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1321
Author(s):  
Cheng-Yun Peng ◽  
Chia-Hung Dylan Tsai
Keyword(s):  
Plasma Treatment ◽  
Treatment Time ◽  
Plasma Jet ◽  
Aging Effect ◽  
Droplet Generation ◽  
Magnetic Actuation ◽  
Pdms Surface ◽  
Polymeric Surface ◽  
Air Jet ◽  
Droplet Manipulation

Droplet manipulation is important in the fields of engineering, biology, chemistry, and medicine. Many techniques, such as electrowetting and magnetic actuation, have been developed for droplet manipulation. However, the fabrication of the manipulation platform often takes a long time and requires well-trained skills. Here we proposed a novel method that can directly generate and manipulate droplets on a polymeric surface using a universal plasma jet. One of its greatest advantages is that the jet can tremendously reduce the time for the platform fabrication while it can still perform stable droplet manipulation with controllable droplet size and motion. There are two steps for the proposed method. First, the universal plasma jet is set in plasma mode for modifying the manipulation path for droplets. Second, the jet is switched to air-jet mode for droplet generation and manipulation. The jetted air separates and pushes droplets along the plasma-treated path for droplet generation and manipulation. According to the experimental results, the size of the droplet can be controlled by the treatment time in the first step, i.e., a shorter treatment time of plasma results in a smaller size of the droplet, and vice versa. The largest and the smallest sizes of the generated droplets in the results are about 6 µL and 0.1 µL, respectively. Infrared spectra of absorption on the PDMS surfaces with and without the plasma treatment are investigated by Fourier-transform infrared spectroscopy. Tests of generating and mixing two droplets on a PDMS surface are successfully achieved. The aging effect of plasma treatment for the proposed method is also discussed. The proposed method provides a simple, fast, and low-cost way to generate and manipulate droplets on a polymeric surface. The method is expected to be applied to droplet-based cell culture by manipulating droplets encapsulating living cells and towards wall-less scaffolds on a polymeric surface.

Conceptual Design of an Experiment for the International Space Station About Shape Memory Composite in Space Environment

2017 ◽  
Author(s):  
Loredana Santo ◽  
Denise Bellisario ◽  
Giovanni Matteo Tedde ◽  
Fabrizio Quadrini
Keyword(s):  
Shape Memory ◽  
International Space Station ◽  
Space Station ◽  
Sun Exposure ◽  
Aging Effect ◽  
Space Environment ◽  
Aging Effects ◽  
Solar Sails ◽  
International Space ◽  
Shape Memory Composite

Shape memory polymers (SMP) and composites (SMPC) may be used for many applications in Space, from self-deployable structures (such as solar sails, panels, shields, booms and antennas), to grabbing systems for Space debris removal, up to new-concept actuators for telescope mirror tuning. Experiments on the International Space Station are necessary for testing prototypes in relevant environment, above all for the absence of gravity which affects deployment of slender structures but also to evaluate the aging effects of the Space environment. In fact, several aging mechanisms are possible, from polymer cracking to cross-linking and erosion, and different behaviors are expected as well, from consolidating the temporary shape to composite degradation. Evaluating the possibility of shape recovery because of sun exposure is another interesting point. In this study, a possible experiment on the ISS is shown with the aim of evaluating the aging effect of Space on material performances. The sample structure is described as well as the testing strategy.

scholarly journals Anti-aging properties of metformin

2021 ◽  
Vol 11 (9) ◽  
pp. 37-42
Author(s):  
Anna Małgorzata Łopuszyńska ◽  
Mateusz Pawlicki ◽  
Magdalena Kozioł ◽  
Aleksandra Krasa ◽  
Ewa Piekarska ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Randomized Trials ◽  
Aging Effect ◽  
Oral Drug ◽  
Aging Effects ◽  
Ampk Signaling ◽  
Anti Cancer ◽  
Aging Properties ◽  
Effects Of Aging

 Introduction: Life expectancy of human population is being constantly prolonged, hence there is a lot of research into drug that will prevent the effects of aging. There are many reports that metformin, which is a drug used in type 2 diabetes, has anti-aging effects. It belongs to the group of biguanides and has been used since the 1950s. It is a relatively safe, cheap and effective drug, which makes it a promising subject for many studies. The purpose of this review is to present the latest developments in this field. Material and methods: PubMed scientific base was searched using following keywords: metformin, aging, anti-aging, in years 2017-2021. Results: Numerous studies show that metformin has an impact on aging through the nutrient pathway, AMPK signaling pathway, and its effects on reactive oxygen species. In addition, it has an anti-cancer effect, inhibiting, among others, rectal cancer cells and p53 mutant colon cancer. Research in rodents has shown that this drug has anti-aging effects on many organs, including the CNS, ovaries, prostate, heart muscle and skin. Conclusions: Metformin, which is the most commonly used oral drug in type 2 diabetes, has many other mechanisms of action. Its anti-aging effect works on many organs in our bodies, which gives hope to find an anti-aging substance. However, multicentre, randomized trials are needed to determine the exact anti-aging dose, its possible side effects, and effects on various organisms. 

scholarly journals Sex-dependent Pathological Aging Effect on Caudate Functional Connectivity in Mild Cognitive Impairment

2021 ◽  
Author(s):  
Zhengshi Yang ◽  
Jessica Z.K. Caldwell ◽  
Jeffrey L. Cummings ◽  
Aaron Ritter ◽  
Jefferson W. Kinney ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Mild Cognitive Impairment ◽  
Functional Connectivity ◽  
Aging Effect ◽  
Analysis Of Covariance ◽  
Aging Effects ◽  
Mixed Effect ◽  
Effect Analysis ◽  
Pathological Aging ◽  
Age Related

Abstract Purpose To assess the pathological aging effect on caudate functional connectivity among mild cognitive impairment (MCI) participants and examine whether and how sex and amyloid contribute to this process. Materials and Methods 277 functional magnetic resonance imaging (fMRI) sessions from 163 cognitive normal (CN) older adults and 309 sessions from 139 participants with MCI were included as the main sample in our analysis. Pearson’s correlation was used to characterize the functional connectivity (FC) between caudate and each brain region, then caudate nodal strength was computed to quantify the overall caudate FC strength. Association analysis between caudate nodal strength and age was carried out in MCI and CN separately using linear mixed effect (LME) model with covariates (education, handedness, sex, Apolipoprotein E4 and intra-subject effect). Analysis of covariance was conducted to investigate sex, amyloid status and their interaction effects on aging with the fMRI data subset having amyloid status available. LME model was applied to women and men separately within MCI group to evaluate aging effects on caudate nodal strength and each region’s connectivity with caudate. We then evaluated the roles of sex and amyloid status in the associations of neuropsychological scores with age or caudate nodal strength. An independent cohort was used to validate the sex-dependent aging effects in MCI. Results The MCI group had significantly stronger age-related increase of caudate nodal strength compared to the CN group. Analyzing women and men separately revealed that the aging effect on caudate nodal strength among MCI participants was significant only for women (left: P=6.23x10−7, right: P=3.37x10−8), but not for men (P>0.3 for bilateral caudate). The aging effects on caudate nodal strength were not significantly mediated by brain amyloid burden. Caudate connectivity with ventral prefrontal cortex substantially contributed to the aging effect on caudate nodal strength in women with MCI. Higher caudate nodal strength is significantly related to worse cognitive performance in women but not in men with MCI. Conclusion Sex modulates the pathological aging effects on caudate nodal strength in MCI regardless of amyloid status. Caudate nodal strength may be a sensitive biomarker of pathological aging in women with MCI.

Hygrothermal aging effect on the properties of PMMA nanocomposites reinforced by ceramic nanoparticles

2021 ◽  
pp. 002199832110539
Author(s):  
Shervin Jodatnia ◽  
Samrand Rash-Ahmadi
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
Mechanical Properties ◽  
Moisture Absorption ◽  
Aging Effect ◽  
Superior Performance ◽  
Multi Criteria Decision Making ◽  
Aging Effects ◽  
Hygrothermal Aging ◽  
Scanning Electron

This paper aimed to evaluate hygrothermal aging effects on polymethyl methacrylate modified with TiO2, SiO2, and Al2O3 nanoparticles in 0.5, 1, and 2% weight fractions. The distribution of nanoparticles was characterized by the scanning electron microscopy (SEM) method. Moisture absorption behavior and mechanical properties of samples in terms of elastic modulus, tensile strength, impact strength, and hardness were investigated. Furthermore, the coefficient of hygrothermal expansion (CHE) for each sample was calculated thanks to experimental data. Finally, by applying the multi-criteria decision making (MCDM) technique, the optimum composition for superior performance was obtained in 0.5 wt% of nanoparticles, more specifically for SiO2.

scholarly journals Studies on Modification of Surface Properties in Polycarbonate (PC) Film Induced by DC Glow Discharge Plasma

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
K. A. Vijayalakshmi ◽  
M. Mekala ◽  
C. P. Yoganand ◽  
K. Navaneetha Pandiyaraj
Keyword(s):  
Contact Angle ◽  
Glow Discharge ◽  
Plasma Treatment ◽  
Polymer Surface ◽  
Peel Test ◽  
Glow Discharge Plasma ◽  
Polar Component ◽  
Air Plasma ◽  
Modified Surface ◽  
Surface Modified

The polycarbonate film (PC) surface was treated using glow discharge low-pressure air plasma. The modified surface was characterized by contact angle, FTIR, XRD, AFM, and XPS analysis. The surface-modified samples were further investigated using T-peel test for technical applications. The surface energy of the sample was estimated by measuring contact angle. The results show that, after plasma treatment, the root mean square (RMS) roughness of PC film was gradually increased with exposure time. Plasma treatment modified the chemical composition of the polymer surface and it made the surface to be highly hydrophilic. It was found that the air plasma treatment increases the polar component of PC film.

scholarly journals Generic Aging Management Programs for License Renewal of BWR Reactor Coolant System Components

2002 ◽  
Author(s):  
V. N. Shah ◽  
Y. Y. Liu
Keyword(s):  
Operating Experience ◽  
Extended Period ◽  
Aging Effect ◽  
Lessons Learned ◽  
Monitoring And Control ◽  
Aging Effects ◽  
Management Activity ◽  
Reactor Coolant ◽  
License Renewal ◽  
Coolant System

The paper reviews the existing generic aging management programs (AMPs) for the reactor coolant system (RCS) components in boiling water reactors (BWRs), including the reactor pressure vessel and internals, the reactor recirculation system, and the connected piping. These programs have been evaluated in the U.S. Nuclear Regulatory Commission (NRC) report, Generic Aging Lessons Learned (GALL), NUREG-1801, for their use in the license renewal process to manage several aging effects, including loss of material, crack initiation and growth, loss of fracture toughness, loss of preload, wall thinning, and cumulative fatigue damage. The program evaluation includes a review of ten attributes (scope of program, preventive actions, parameters monitored/inspected, detection of aging effects, monitoring and trending, acceptance criteria, corrective actions, confirmative process, administrative control, and operating experience) for their effectiveness in managing a specific aging effect in a given component(s). The generic programs are based on the ASME Section XI inservice inspection requirements; industry guidelines for inspection and evaluation of aging effects in BWR reactor vessel, internals, and recirculation piping; monitoring and control of BWR water chemistry; and operating experience as reported in the USNRC generic communications and industry reports. The review concludes that all generic AMPs are acceptable for managing aging effects in BWR RCS components during an extended period of operation and do not need further evaluation. However, the plant-specific programs for managing aging in certain RCS components during an extended period of operation do require further evaluation. For some plant-specific AMPs, the GALL report recommends an aging management activity to verify their effectiveness. An example of such an activity is a one-time inspection of Class 1 small-bore piping to ensure that service-induced weld cracking is not occurring in the piping. Several of the AMPs, which do not require further evaluation, do need enhancements to allow for an extended period of reactor operation. The paper concludes that the GALL report systematically evaluates the generic AMPs for their effectiveness during an extended period of operation and provides a technical basis for their acceptance. The use of the GALL report should facilitate both preparation of a license renewal application and timely and uniform review by the NRC staff.

Surface Modification of Poly(Ethylene Terephthalate) in Air Plasma

2019 ◽  
Vol 27 (1) ◽  
pp. 128-136
Author(s):  
Mioara Drobota ◽  
Alexandru Trandabat ◽  
Marius Pislaru
Keyword(s):  
Contact Angle ◽  
Room Temperature ◽  
Ethylene Terephthalate ◽  
Film Surface ◽  
Air Plasma ◽  
Poly Ethylene Terephthalate ◽  
Modified Surface ◽  
Poly Ethylene ◽  
Pet Films ◽  
Polyester Film

Abstract This paper reports the modification of a polyester film surface in air plasma at room temperature. In order to evaluate the efficiency of the plasma treatment, the modified surface of the PET films was characterized by contact angle and ATR-FTIR spectroscopy.

Improving the Electrokinetic Properties of PDMS With Surface Treatments

2010 ◽  
Author(s):  
Zeyad Almutairi ◽  
Carolyn Ren ◽  
Leonardo Simon
Keyword(s):  
Fluid Flow ◽  
Zeta Potential ◽  
Electric Double Layer ◽  
Electroosmotic Flow ◽  
Fast Response ◽  
Ionic Concentration ◽  
Microfluidic Chips ◽  
Electrokinetic Properties ◽  
Electroosmotic Pumping ◽  
Hydrophobic Nature

PDMS (Polydimethylsiloxane) is widely used as a microfluidic chip material for various applications due to its desirable properties [1, 2]. However PDMS has several drawbacks that limit its utilization in a number of microfluidic applications [1–4]. Properties such as the hydrophobic nature, sample absorption, and low electrokinetic properties (low zeta potential) are some issues that must be considered before using PDMS for numerous applications [3]. In many PDMS based chips electroosmotic pumping is used for fluid flow and sample transport along the microchannel networks. Simplicity of implementation in microfluidic chips, fast response time, and the plug-like velocity profile are the major advantages of electroosmotic flow compared to other fluid pumping techniques [2]. This type of flow utilizes the formation of electric double layer (EDL) in microchannels and the movement of ions under an applied external electric field. Thus, the surface properties of the channel material and liquid properties (ionic concentration, pH, and viscosity) play major roles in electroosmotic pumping for different solutions in microchannels.

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