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1.
EBioMedicine ; 46: 133-149, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31375425

RESUMO

BACKGROUND: The evaluation for surgical resectability of pancreatic ductal adenocarcinoma (PDAC) patients is not only imaging-based but highly subjective. An objective method is urgently needed. We report on the clinical value of a phenotypic circulating tumor cell (CTC)-based blood test for a preoperative prognostic assessment of tumor metastasis and overall survival (OS) of PDAC patients. METHODS: Venous blood samples from 46 pathologically confirmed PDAC patients were collected prospectively before surgery and immunoassayed using a specially designed TU-chip™. Captured CTCs were differentiated into epithelial (E), mesenchymal and hybrid (H) phenotypes. A further 45 non-neoplastic healthy donors provided blood for cell line validation study and CTC false positive quantification. FINDINGS: A validated multivariable model consisting of disjunctively combined CTC phenotypes: "H-CTC≥15.0 CTCs/2ml OR E-CTC≥11.0 CTCs/2ml" generated an optimal prediction of metastasis with a sensitivity of 1.000 (95% CI 0.889-1.000) and specificity of 0.886 (95% CI 0.765-0.972). The adjusted Kaplan-Meier median OS constructed using Cox proportional-hazard models and stratified for E-CTC < 11.0 CTCs/2 ml was 16.5 months and for E-CTC ≥ 11.0 CTCs/2 ml was 5.5 months (HR = 0.050, 95% CI 0.004-0.578, P = .016). These OS results were consistent with the outcome of the metastatic analysis. INTERPRETATION: Our work suggested that H-CTC is a better predictor of metastasis and E-CTC is a significant independent predictor of OS. The CTC phenotyping model has the potential to be developed into a reliable and accurate blood test for metastatic and OS assessments of PDAC patients. FUND: National Natural Science Foundation of China; Zhejiang Province Science and Technology Program; China Scholarship Council.


Assuntos
Biomarcadores Tumorais , Carcinoma Ductal Pancreático/diagnóstico , Carcinoma Ductal Pancreático/mortalidade , Imunofenotipagem , Células Neoplásicas Circulantes/metabolismo , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/mortalidade , Linhagem Celular Tumoral , Feminino , Humanos , Estimativa de Kaplan-Meier , Masculino , Metástase Neoplásica , Estadiamento de Neoplasias , Células Neoplásicas Circulantes/patologia , Fenótipo , Prognóstico , Modelos de Riscos Proporcionais , Reprodutibilidade dos Testes
2.
J Mech Behav Biomed Mater ; 95: 34-40, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30953807

RESUMO

From a series of experimental measurements and supplemented by results from a computational model, we investigated the static and dynamic size dependent behaviors of a single-strand polycaprolactone (PCL) nanofiber. For the static bending, the fiber stiffness showed a dramatic increase as the fiber diameter is reduced and for the dynamic bending, the resonant frequency exhibited a very similar trend. Employing the strain gradient (SG) theory, we formulated a model that not only accurately captures the magnitude of the experimentally observed size dependent response but it is also, able to correctly predict the onset of the inverse square behavior. Both our experimental data and SG model results showed that the damping term is unaffected by the size-dependency. We introduced an experimentally calibrated fiber length scale parameter to predict the onset and rise of the size dependent response and an effective elastic modulus to characterize the stiffness increase. This understanding of the pronounced enhancement in nanofibers can be used to design a nanofibrous scaffold to keep its structural integrity intact against a sudden static pull of a seeded cell or when subjected to a dynamic loading environment from say, the pulsating peripheral blood.

3.
Adv Mater ; 30(32): e1802074, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29952034

RESUMO

Recently, commercial graphite and other carbon-based materials have shown promising properties as the anode for potassium-ion batteries. A fundamental problem related to those carbon electrodes, significant volume expansion, and structural instability/collapsing caused by cyclic K-ion intercalation, remains unsolved and severely limits further development and applications of K-ion batteries. Here, a multiwalled hierarchical carbon nanotube (HCNT) is reported to address the issue, and a reversible specific capacity of 232 mAh g-1 , excellent rate capability, and cycling stability for 500 cycles are achieved. The key structure of the HCNTs consists of an inner CNT with dense-stacked graphitic walls and a loose-stacked outer CNT with more disordered walls, and individual HCNTs are further interconnected into a hyperporous bulk sponge with huge macropore volume, high conductivity, and tunable modulus. It is discovered that the inner dense-CNT serves as a robust skeleton, and collectively, the outer loose-CNT is beneficial for K-ion accommodation; meanwhile the hyperporous sponge facilitates reaction kinetics and offers stable surface capacitive behavior. The hierarchical carbon nanotube structure has great potential in developing high-performance and stable-structure electrodes for next generation K and other metal-ion batteries.

4.
Cancer Res ; 78(14): 4073-4085, 2018 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-29789419

RESUMO

The increasing incidence of bladder cancer and its high rate of recurrence over a 5-year period necessitate the need for diagnosis and surveillance amelioration. Cystoscopy and urinary cytology are the current tools, and molecular techniques such as BTA stat, NMP22, survivin mRNA, and urovysion FISH have attracted attention; however, they suffer from insufficient sensitivity or specificity. We developed a novel microfluidic approach for harvesting intact urinary-exfoliated tumor cells (UETC), either individually or in clusters, in a clean and segregated environment, which is crucial to minimize cross-contamination and misreads. To reliably and accurately identify UETC, our quantitative immunoassay involved concurrent use of two oncoproteins CK20 and CD44v6 antigen. CK20 is an intermediate filament protein overexpressed in urothelial tumors, and CD44v6 is a membrane adhesion molecule closely associated with cell invasion, tumor progression, and metastatic spread. Single-cell whole-genome sequencing on 12 captured UETCs and copy number alteration analysis showed that 11/12 (91.7%) of the immunofluorescence-identified UETCs possessed genomic instability. A total of 79 patients with bladder cancer and 43 age-matched normal controls (NC) were enrolled in the study. We detected considerably higher UETC counts in patients with bladder cancer versus the NC group [53.3 (10.7-1001.9) vs. 0.0 (0-3.0) UETCs/10 mL; P < 0.0001]. For bladder cancer detection, a stratified 10-fold cross-validation of training data reveals an overall predictive accuracy of 0.84 [95% confidence interval (CI), 0.76-0.93] with an 89.8% (95% CI, 71.5%-86.4%) for sensitivity and 71.5% (95% CI, 59.7%-83.3%) for specificity. Overall, the microfluidic immunoassay demonstrates increased sensitivity and specificity compared with other techniques for the detection of bladder cancer.Significance: A unique and promising diagnostic assay for bladder cancer is proposed with potential clinical utility as a complement for cytology. Cancer Res; 78(14); 4073-85. ©2018 AACR.


Assuntos
Variações do Número de Cópias de DNA/genética , Neoplasias da Bexiga Urinária/genética , Neoplasias da Bexiga Urinária/patologia , Idoso , Antígenos de Neoplasias/genética , Estudos de Casos e Controles , Linhagem Celular Tumoral , Cistoscopia/métodos , DNA/genética , Feminino , Humanos , Imunoensaio/métodos , Masculino , Microfluídica/métodos , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/genética , Recidiva Local de Neoplasia/patologia , Sensibilidade e Especificidade , Análise de Célula Única/métodos , Bexiga Urinária/patologia
5.
ACS Appl Mater Interfaces ; 10(17): 14622-14631, 2018 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-29652482

RESUMO

Heterogeneous nanostructuring of MoSe2 over a carbon nanotube (CNT) sponge as a free-standing electrode not only brings higher performance but also eliminates the need for dead elements such as a binder, conductive carbon, and supportive current collectors. Further, the porous CNT sponge can be easily compacted via an intense densification of the active material MoSe2 to produce an electrode with a high mass loading for a significantly improved areal capacity. In this work, we present a tunable coating of MoSe2 on a CNT sponge to fabricate a core-shell MoSe2@CNT anode. The three-dimensional nanotubular sponge is synthesized via a solvothermal process, followed by thermal annealing to improve crystallization. Structural and morphological studies revealed that MoSe2 grew as a layered structure ( d = 0.66 nm), where numbers of layers can be controlled to yield optimized results for Li+ storage. We showed that the 10-layer core-shell CNT@MoSe2 hybrid sponge delivered a discharge capacity of 820.5 mAh g-1 after 100 cycles at 100 mA g-1 with a high cyclic stability and rate capability. Further, an ex situ structural and morphological analysis revealed that ionic storage causes a phase change in MoSe2 from a crystalline to a partial amorphous state for a continuous increase in the capacity with extended cycling. We believe that the strategy developed here will assist users to tune the electrode materials for future energy-storage devices, especially how the materials are changing with the passage of time and their effects on the device performance.

6.
Oncotarget ; 9(7): 7522-7533, 2018 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-29484129

RESUMO

Lacking a satisfactory screening test, ovarian cancer is frequently diagnosed at a late stage, leading to poor patient outcomes. This study investigated the diagnostic value of circulating tumor cells (CTCs) in peripheral blood from patients with suspected ovarian tumors. Sixty-one women suspected of having an ovarian mass were prospectively enrolled in this study. CTCs were identified and counted using microfluidic isolation and immunofluorescent staining of CD45, HE4, and epithelial and mesenchymal (E&M) markers (epithelial cell adhesion molecule, cytokeratins, and vimentin). Thirty (49%) of the patients were diagnosed with ovarian cancer. DAPI+/E&M+/CD45-/HE4+ CTC counts were higher in these patients than in patients with benign tumors (p = 0.016). The receiver operating characteristic (ROC) curve showed that the sensitivity of CTCs was 73.3%, which was superior to that of CA125 (56.7%). In patients with elevated CA125 levels (≥35 U/ml), CTC counts still showed good specificity (86.7%). Our findings suggest the DAPI+/E&M+/CD45-/HE4+ CTC count is a useful diagnostic indicator in patients with suspected ovarian cancer.

7.
Respir Physiol Neurobiol ; 249: 23-31, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29294356

RESUMO

The study aims to study the effects of short duration deep breathing on the EEG power with topography based on parallel group randomized controlled trial design which was lacking in prior reports. 50 participants were split into 4 groups: control (CONT), deep breathing (DB) for 5 (DB5), 7 (DB7), and 9 (DB9) minutes. EEG recordings were obtained during baseline, deep breathing session, after deep breathing, and a follow-up session after 7 days of consecutive practice. Frontal theta power of DB5 and DB9 was significantly larger than that of CONT after the deep breathing session (p = 0.027 and p = 0.006, respectively) and the profound finding showed that the theta topography obtained a central-focused distribution for DB7 and DB9. The result obtained was consistent with previous literature, albeit for certain deep breathing durations only, indicating a possible linkage between the deep breathing duration and the neurophysiology of the brain.


Assuntos
Mapeamento Encefálico , Exercícios Respiratórios/métodos , Potenciais Evocados/fisiologia , Respiração , Adulto , Eletroencefalografia , Feminino , Humanos , Masculino , Fatores de Tempo , Adulto Jovem
8.
J Mech Behav Biomed Mater ; 77: 314-320, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28961518

RESUMO

The stiffness of a nano-fibrous scaffold is generally enhanced due to the size-dependency of the thin nanofibers contained in the scaffold. We proposed a model that incorporates size-dependency of single nanofibers to predict the scaffold effective modulus, in which the fibers' random or orientation distribution are considered. In the model the fiber segments between rigid fiber-fiber bonds can be stretching, shearing and bending. Using deformation energy equilibrium between sum of individual fibers and the plate of nano-fibrous scaffold, the scaffold effective modulus was derived explicitly. The model was verified via finite element analysis (FEA) and published experimental results. The parametric studies revealed that the fiber diameter is the dominant parameter to stiffen the scaffold beyond the fiber density and fiber aspect ratio when the fiber diameter is reduced below the onset value of size-dependencies. As a result, the scaffold stiffness can maintain its higher value and lower decrease rate because of the size-dependency with a decreasing diameter of the nanofiber as a result of biodegradation. This inspires the idea of selecting nanofibers near the onset value of size-dependency to obtain a controlled tuning of the scaffold stiffness in the design of novel nano-fibrous scaffolds.


Assuntos
Módulo de Elasticidade , Teste de Materiais/métodos , Nanofibras/química , Polímeros/química , Engenharia Tecidual/métodos , Tecidos Suporte/química , Materiais Biocompatíveis/química , Análise de Elementos Finitos , Poliésteres/química , Estresse Mecânico , Resistência à Tração
9.
Biomaterials ; 150: 112-124, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29035737

RESUMO

Traditionally, liquid biopsy is a blood test involving the harvesting of tumor materials from peripheral blood. Tumor cells from non-blood body fluids have always been clinically available in cytological examinations but limited for use in differential diagnosis due to the low sensitivity of conventional cytopathology. With the recent significant progress in microfluidic and downstream molecular technologies, liquid biopsies have now evolved to include harvesting tumor cells and DNA fragments in all kinds of non-blood body fluids. This expansion into general body fluids presages the notion that liquid biopsy could soon be used in competition, as well as, in complementarity with tissue biopsy. Preliminary research of fluid-harvested tumor materials to spot early-stage tumors, monitor disease progression for metastasis and recurrence, and detect chemoresistance have been reported. To reflect the propagation of tumor cells in non-blood body fluids, we introduced the term Mobile Tumor Cells (MTCs), in lieu of the widely accepted term of circulating tumor cells (CTCs) resident in the bloodstream. Our review starts with a discussion on the clinical significance of MTCs, followed by a presentation of microfluidic techniques for MTC capture and various strategies for their identification. Hopefully, the phenotypic and genomic data acquired from harvested MTCs can be used to guide and improve cancer treatment decisions.


Assuntos
Líquidos Corporais/citologia , Biópsia Líquida/métodos , Microfluídica/métodos , Neoplasias/diagnóstico , Células Neoplásicas Circulantes/patologia , Humanos , Análise de Sequência de DNA , Análise de Célula Única
10.
PeerJ ; 5: e3857, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29018605

RESUMO

OBJECTIVES: Practitioners of mindfulness are reported to have greater cognitive control especially in conflict monitoring, response inhibition and sustained attention. However, due to the various existing methods in each mindfulness practices and also, the high commitment factor, a barrier still exists for an individual to pick up the practices. Therefore, the effect of short duration deep breathing on the cognitive control is investigated here. METHODS: Short duration guided deep breathing videos consisting of 5, 7 and 9 min respectively were created and used on subjects training. The effect on cognitive control was assessed using a Go/NoGo task along with event-related potential (ERP) measurements at Fz, Cz, and Pz. RESULTS: From the study, the significant outcome showed at the follow-up session in which participants engaged for 5 min deep breathing group showed a profound NoGo N2 amplitude increment as compared to the control group, indicating an enhanced conflict monitoring ability. An inverse relationship between the NoGo N2 amplitude and the breathing duration is observed as well at the follow-up session. CONCLUSION: These results indicated the possibility of performing short duration deep breathing guided by a video to achieve an enhanced conflict monitoring as an alternative to other mindfulness practices and 5 min is found to be the optimum practice duration. SIGNIFICANT: This study is the first to establish a relationship between deep breathing and conflict monitoring through ERP. The study population of young adults taken from the same environment reduces the variance in ERP results due to age and environment. LIMITATION: A larger sample size would provide a greater statistical power. A longer duration of deep breathing should be investigated to further clarify the relationship between the practice duration and the NoGo N2 amplitude. The result can be split by gender and analyzed separately due to the different brain structure of males and females.

11.
PLoS One ; 12(7): e0181249, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28704506

RESUMO

BACKGROUND: Circulating endothelial cells (CECs) are widely reported as a promising biomarker of endothelial damage/dysfunction in coronary artery disease (CAD). The two popular methods of CEC quantification include the use of immunomagnetic beads separation (IB) and flow cytometry analysis (FC); however, they suffer from two main shortcomings that affect their diagnostic and prognostic responses: non-specific bindings of magnetic beads to non-target cells and a high degree of variability in rare cell identification, respectively. We designed a microfluidic chip with spatially staggered micropillars for the efficient harvesting of CECs with intact cellular morphology in an attempt to revisit the diagnostic goal of CEC counts in CAD patients with angina pectoris. METHODS: A label-free microfluidic assay that involved an in-situ enumeration and immunofluorescent identification (DAPI+/CD146+/VEGFR1+/CD45-) of CECs was carried out to assess the CEC count in human peripheral blood samples. A total of 55 CAD patients with angina pectoris [16 with chronic stable angina (CSA) and 39 with unstable angina (UA)], together with 15 heathy controls (HCs) were enrolled in the study. RESULTS: CEC counts are significantly higher in both CSA and UA groups compared to the HC group [respective medians of 6.9, 10.0 and 1.5 cells/ml (p < 0.01)]. Further, a significant elevation of CEC count was observed in the three UA subgroups [low risk (5.3) vs. intermediate risk (10.8) vs. high risk (18.0) cells/ml, p < 0.001) classified in accordance to the TIMI NSTEMI/UA risk score system. From the receiver-operating characteristic curve analysis, the AUCs for distinguishing CSA and UA from HC were 0.867 and 0.938, respectively. The corresponding sensitivities were 87.5% and 84.6% and the specificities were 66.7% and 86.7%, respectively. CONCLUSIONS: Our microfluidic assay system is efficient and stable for CEC capture and enumeration. The results showed that the CEC count has the potential to be a promising clinical biomarker for the assessment of endothelial damage/dysfunction in CAD patients with angina pectoris.


Assuntos
Angina Pectoris/sangue , Células Sanguíneas/citologia , Doença da Artéria Coronariana/sangue , Células Endoteliais/citologia , Endotélio Vascular/citologia , Microfluídica/métodos , Idoso , Angina Pectoris/complicações , Angina Pectoris/diagnóstico , Biomarcadores/sangue , Contagem de Células Sanguíneas , Estudos de Casos e Controles , Separação Celular/métodos , Células Cultivadas , Doença da Artéria Coronariana/complicações , Doença da Artéria Coronariana/diagnóstico , Feminino , Células Endoteliais da Veia Umbilical Humana/citologia , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico
12.
Adv Mater ; 28(46): 10175-10181, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27690278

RESUMO

Heterogeneous inorganic nanotube structures consisting of multiwalled carbon nanotubes coated by long, continuous MoS2 sheets with tunable sheet number are synthesized using a carbon-nanotube sponge as a template. The resulting 3D porous hybrid sponges have potential applications as high-performance freestanding anodes for Li-ion batteries with excellent specific capacity and cycling stability.

13.
Nat Commun ; 6: 8031, 2015 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-26271603

RESUMO

Harnessing random micromeso-scale ambient energy is not only clean and sustainable, but it also enables self-powered sensors and devices to be realized. Here we report a robust and self-powered kinematic vector sensor fabricated using highly pliable organic films that can be bent to spread over curved and uneven surfaces. The device derives its operational energy from a close-proximity triboelectrification of two surfaces: a polytetrafluoroethylene film coated with a two-column array of copper electrodes that constitutes the mover and a polyimide film with the top and bottom surfaces coated with a two-column aligned array of copper electrodes that comprises the stator. During relative reciprocations, the electrodes in the mover generate electric signals of ±5 V to attain a peak power density of ≥65 mW m(-2) at a speed of 0.3 ms(-1). From our 86,000 sliding motion tests of kinematic measurements, the sensor exhibits excellent stability, repeatability and strong signal durability.

14.
J Mech Behav Biomed Mater ; 42: 26-31, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25460923

RESUMO

As the name implies, tensile size-dependency refers to the size-dependent response under uniaxial tension. It defers markedly from bending size-dependency in terms of onset and magnitude of the size-dependent response; the former begins earlier but rises to a smaller value than the latter. Experimentally, tensile size-dependent behavior is much harder to capture than its bending counterpart. This is also true in the computational effort; bending size-dependency models are more prevalent and well-developed. Indeed, many have questioned the existence of tensile size-dependency. However, recent experiments seem to support the existence of this phenomenon. Current strain gradient elasticity theories can accurately predict bending size-dependency but are unable to track tensile size-dependency. To rectify this deficiency a higher-order strain gradient elasticity model is constructed by including the second gradient of the strain into the deformation energy. Tensile experiments involving 10 wt% polycaprolactone nanofibers are performed to calibrate and verify our model. The results reveal that for the selected nanofibers, their size-dependency begins when their diameters reduce to 600 nm and below. Further, their characteristic length-scale parameter is found to be 1095.8 nm.


Assuntos
Elasticidade , Teste de Materiais , Nanofibras , Poliésteres/química , Resistência à Tração , Modelos Teóricos , Estresse Mecânico
15.
ACS Nano ; 8(4): 3836-42, 2014 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-24601567

RESUMO

Reciprocating motion is a widely existing form of mechanical motion in natural environment. In this work we reported a case-encapsulated triboelectric nanogenerator (cTENG) based on sliding electrification to convert reciprocating motion into electric energy. Patterned with multiple sets of grating electrodes and lubricated with polytetrafluoroethylene (PTFE) nanoparticles, the cTENG exported an average effective output power of 12.2 mW over 140 kΩ external load at a sliding velocity of 1 m/s, in corresponding to a power density of 1.36 W/m(2). The sliding motion can be induced by direct-applied forces as well as inertia forces, enabling the applicability of the cTENG in addressing ambient vibration motions that feature large amplitude and low frequency. The cTENG was demonstrated to effectively harvest energy from human body motions and wavy water surface, indicating promising prospects of the cTENG in applications such as portable and stand-alone self-powered electronics.


Assuntos
Fontes de Energia Elétrica , Movimento (Física) , Nanotecnologia/instrumentação , Cápsulas , Condutividade Elétrica , Análise de Elementos Finitos , Humanos , Movimento , Nanopartículas , Politetrafluoretileno/química
16.
Biomicrofluidics ; 7(3): 34109, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24404029

RESUMO

For cancer patients, the enumeration of rare circulating tumor cells (CTCs) in peripheral blood is a strong prognostic indicator of the severity of the cancer; for the general population, the capture of CTCs is needed for use as a clinical tool for cancer screening, early detection, and treatment assessment. Here, we present a fast, high-purity (∼90%) and high-efficiency (>90%) method for the segregation and undamaged recovery of CTCs using a spatially gradated microfluidic chip. Further, by lysing the red blood cells we achieved not only a significant reduction in the overall processing time but also mitigated the blood clogging problem commonly encountered in microfluidic-based CTC isolation systems. To clinically validate the chip, we employed it to detect and capture CTCs from 10 liver cancer patients. Positive CTC enumeration was observed in all the blood samples, and the readings ranged from a low of 1-2 CTCs (1 patient) to a high of >20 CTCs (2 patients) with the balance having 3-20 CTCs per 3-ml blood sample. The work here indicates that our system can be developed for use in cancer screening, metastatic assessment, and chemotherapeutic response and for pharmacological and genetic evaluation of single CTCs.

17.
ACS Nano ; 5(2): 1476-82, 2011 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-21194200

RESUMO

A method for the large-scale fabrication of patterned organic nanowire (NW) arrays is demonstrated by the use of laser interference patterning (LIP) in conjunction with inductively coupled plasma (ICP) etching. The NW arrays can be fabricated after a short ICP etching of periodic patterns produced through LIP. Arrays of NWs have been fabricated in UV-absorbent polymers, such as PET (polyethylene terephthalate) and Dura film (76% polyethylene and 24% polycarbonate), through laser interference photon ablation and in UV transparent polymers such as PVA (polyvinyl acetate) and PP (polypropylene) through laser interference lithography of a thin layer of photoresist coated atop the polymer surface. The dependence of the structure and morphology of NWs as a function of initial pattern created by LIP and the laser energy dose in LIP is discussed. The absence of residual photoresist atop the NWs in UV-transparent polymers is confirmed through Raman spectroscopy.


Assuntos
Nanotecnologia/métodos , Nanofios/química , Polímeros/química , Lasers , Raios Ultravioleta
18.
Nanotechnology ; 19(45): 455706, 2008 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-21832795

RESUMO

We present a strain gradient (SG) theory to explain the strongly inverse size dependence between the elastic modulus and fiber diameter in polymeric nanofibers. For centrosymmetric and isotropic materials we showed that the three length-scale parameters can be combined into a single parameter that can be used to predict the onset of the size-dependent trend when the fiber diameter is reduced past its critical size. To address the issue of whether the SG offers a plausible explanation of the size-dependent behavior we conducted a series of uniaxial tensile and static bending tests involving polycaprolactone nanofibers. Since the elastic modulus is highly sensitive to the fiber diameter, it is necessary to correct the experimental data to account for the lack of circularity in the cross-section of the real fiber. Additionally, we applied the SG model to study the size-dependent elastic properties of polypyrrole nanotubes. By approaching the SG theory from a dynamics point of view, our model is able to capture size-dependent effects in the mechanics of fine-scale materials for both static and dynamic responses.

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