Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 38
Filtrar
1.
Sensors (Basel) ; 23(24)2023 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-38139573

RESUMO

Skin-based wearable devices have gained significant attention due to advancements in soft materials and thin-film technologies. Nevertheless, traditional wearable electronics often entail expensive and intricate manufacturing processes and rely on metal-based substrates that are susceptible to corrosion and lack flexibility. In response to these challenges, this paper has emerged with an alternative substrate for wearable electrodes due to its cost-effectiveness and scalability in manufacturing. Paper-based electrodes offer an attractive solution with their inherent properties of high breathability, flexibility, biocompatibility, and tunability. In this study, we introduce carbon nanotube-based paper composites (CPC) electrodes designed for the continuous detection of biopotential signals, such as electrooculography (EOG), electrocardiogram (ECG), and electroencephalogram (EEG). To prevent direct skin contact with carbon nanotubes, we apply various packaging materials, including polydimethylsiloxane (PDMS), Eco-flex, polyimide (PI), and polyurethane (PU). We conduct a comparative analysis of their signal-to-noise ratios in comparison to conventional gel electrodes. Our system demonstrates real-time biopotential monitoring for continuous health tracking, utilizing CPC in conjunction with a portable data acquisition system. The collected data are analyzed to provide accurate heart rates, respiratory rates, and heart rate variability metrics. Additionally, we explore the feasibility using CPC for sleep monitoring by collecting EEG signals.


Assuntos
Nanotubos de Carbono , Dispositivos Eletrônicos Vestíveis , Nanotubos de Carbono/química , Pele , Eletrodos , Sono , Eletrocardiografia
2.
Biomed Microdevices ; 22(3): 50, 2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32725281

RESUMO

For point-of-care diagnosis of tuberculosis (TB), current TB diagnostic approaches need to be further improved for achieving an accurate diagnosis that is rapid and low-cost. This paper presents an immuno-resistive sensor on a plastic film for inexpensive, simple TB screening. The sensor is composed of single-walled carbon nanotubes (SWCNTs) functionalized with polyclonal antibodies raised against the MPT64 surface antigen from Mycobacterium tuberculosis (MTB). The target analyte of either MTB or MPT64 is spiked in tongue swab and sputum samples. Under optimized conditions, targets are directly detected from tongue swab samples by resistive measurement. Target analytes spiked into human sputa are enriched with a magnetic bead protocol followed by resistive detection. This highly sensitive film sensor will facilitate rapid TB screening with the added benefits of a small form factor, simple operation, low power requirement, and low cost.


Assuntos
Programas de Rastreamento/instrumentação , Nanotubos de Carbono/química , Testes Imediatos , Tuberculose/diagnóstico , Humanos , Mycobacterium tuberculosis/imunologia , Mycobacterium tuberculosis/isolamento & purificação , Mycobacterium tuberculosis/fisiologia , Plásticos/química , Escarro/microbiologia
3.
Nanotechnology ; 29(33): 335304, 2018 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-29808828

RESUMO

Single-walled carbon nanotubes (SWCNTs) are used as a key component for chemical sensors. For miniature scale design, a continuous printing method is preferred for electrical conductance without damaging the substrate. In this paper, a non-contact capillary pen printing method is presented by the formation of a nanoink bridge between the nib of a capillary pen and a polyethylene terephthalate film. A critical parameter for stable printing is the advancing contact angle at the bridge meniscus, which is a function of substrate temperature and printing speed. The printed pattern including dots, lines, and films of SWCNTs are characterized by morphology, optical transparency, and electrical properties. Gas and pH sensors fabricated using the non-contact printing method are demonstrated as applications.

4.
Sensors (Basel) ; 17(1)2016 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-28025540

RESUMO

Nanostructured tip-shaped biosensors have drawn attention for biomolecule detection as they are promising for highly sensitive and specific detection of a target analyte. Using a nanostructured tip, the sensitivity is increased to identify individual molecules because of the high aspect ratio structure. Various detection methods, such as electrochemistry, fluorescence microcopy, and Raman spectroscopy, have been attempted to enhance the sensitivity and the specificity. Due to the confined path of electrons, electrochemical measurement using a nanotip enables the detection of single molecules. When an electric field is combined with capillary action and fluid flow, target molecules can be effectively concentrated onto a nanotip surface for detection. To enhance the concentration efficacy, a dendritic nanotip rather than a single tip could be used to detect target analytes, such as nanoparticles, cells, and DNA. However, reproducible fabrication with relation to specific detection remains a challenge due to the instability of a manufacturing method, resulting in inconsistent shape. In this paper, nanostructured biosensors are reviewed with our experimental results using dendritic nanotips for sequence specific detection of DNA. By the aid of the Six Sigma approach, the fabrication yield of dendritic nanotips increases from 20.0% to 86.6%. Using the nanotips, DNA is concentrated and detected in a sequence specific way with the detection limit equivalent to 1000 CFU/mL. The pros and cons of a nanotip biosensor are evaluated in conjunction with future prospects.


Assuntos
Técnicas Biossensoriais/métodos , Nanoestruturas/química , Nanotecnologia/métodos , DNA/química , Limite de Detecção , Análise Espectral Raman
5.
Anal Bioanal Chem ; 407(25): 7673-80, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26231690

RESUMO

Multi-drug resistant tuberculosis (MDR-TB) has become a serious concern for proper treatment of patients. As a phenotypic method, dielectrophoresis can be useful but is yet to be attempted to evaluate Mycobacterium tuberculosis complex cells. This paper investigates the dielectrophoretic behavior of Mycobacterium bovis (Bacillus Calmette-Guérin, BCG) cells that are treated with heat or antibiotics rifampin (RIF) or isoniazid (INH). The experimental parameters are designed on the basis of our sensitivity analysis. The medium conductivity (σ(m)) and the frequency (f) for a crossover frequency (f(xo1)) test are decided to detect the change of σ(m)-f(xo1) in conjunction with the drug mechanism. Statistical modeling is conducted to estimate the distributions of viable and nonviable cells from the discrete measurement of f (xo1). Finally, the parameters of the electrophysiology of BCG cells, C(envelope) and σ(cyto), are extracted through a sampling algorithm. This is the first evaluation of the dielectrophoresis (DEP) approach as a means to assess the effects of antimicrobial drugs on M. tuberculosis complex cells.


Assuntos
Antituberculosos/farmacologia , Eletroforese/instrumentação , Isoniazida/farmacologia , Mycobacterium bovis/efeitos dos fármacos , Mycobacterium tuberculosis/efeitos dos fármacos , Rifampina/farmacologia , Tuberculose/veterinária , Animais , Farmacorresistência Bacteriana Múltipla , Desenho de Equipamento , Temperatura Alta , Humanos , Testes de Sensibilidade Microbiana , Mycobacterium bovis/citologia , Mycobacterium tuberculosis/citologia , Tuberculose/tratamento farmacológico , Tuberculose/microbiologia
6.
J Micromech Microeng ; 25: 055013, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26097292

RESUMO

Tuberculosis (TB) has been a major public health problem, which can be better controlled by using accurate and rapid diagnosis in low-resource settings. A simple, portable, and sensitive detection method is required for point-of-care (POC) settings. This paper studies an amperometric biosensor using a microtip immunoassay for a rapid and low cost detection of Mycobacterium Tuberculosis (MTB) in sputum. MTB in sputum is specifically captured on the functionalized microtip surface and detected by electric current. According to the numerical study, the current signal on microtip surface is linearly changed with increasing immersion depth. Using a reference microtip, the immersion depth is compensated for a sensing microtip. On the microtip surface, target bacteria are concentrated and organized by a coffee ring effect, which amplifies the electric current. To enhance the signal-to-noise ratio, both the sample processing- and rinsing steps are presented with use of deionized water as a medium for the amperometric measurement. When applied to cultured MTB cells spiked into human sputum, the detection limit was 100 CFU/mL, comparable to a more labor-intensive fluorescence detection method reported previously.

7.
Analyst ; 139(6): 1340-4, 2014 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-24482797

RESUMO

Immunoassays analyzing interactions between antigens and antibodies can be affected by capillary action together with binding affinity. This paper studies contact-angle changes of bacterial suspensions on antibody immobilized surfaces. The capillary action and the dried pattern of the bacterial suspensions are analyzed and correlated with specific- and nonspecific bindings between bacteria and antibodies.


Assuntos
Anticorpos Imobilizados/química , Complexo Antígeno-Anticorpo/imunologia , Escherichia coli/isolamento & purificação , Imunoensaio/instrumentação , Mycobacterium bovis/isolamento & purificação , Animais , Bovinos , Desenho de Equipamento , Escherichia coli/imunologia , Infecções por Escherichia coli/microbiologia , Mycobacterium bovis/imunologia , Tuberculose Bovina/microbiologia
8.
Analyst ; 138(11): 3135-8, 2013 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-23594970

RESUMO

A single-step concentration and elution method is developed for detection of DNA in buffer, saliva, and blood. A nanotip capturing DNA using an electric field and capillary action is directly dissolved in buffer for qPCR analysis. The concentration yield and the relative parameters are compared with those of a commercial kit.


Assuntos
Métodos Analíticos de Preparação de Amostras/métodos , DNA/genética , DNA/isolamento & purificação , Nanotecnologia/métodos , Reação em Cadeia da Polimerase/métodos , Bacteriófago lambda/genética , Compostos Inorgânicos de Carbono/química , DNA/análise , DNA/sangue , DNA Viral/análise , DNA Viral/genética , Genoma Humano/genética , Humanos , Nanofios/química , Saliva/química , Compostos de Silício/química , Fatores de Tempo
9.
Nanotechnology ; 24(18): 185502, 2013 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-23579415

RESUMO

Rapid and sensitive detection of low-abundance viral particles is strongly demanded in health care, environmental control, military defense, and homeland security. Current detection methods, however, lack either assay speed or sensitivity, mainly due to the nanosized viral particles. In this paper, we compare a dendritic, multi-terminal nanotip ('dendritic nanotip') with a single terminal nanotip ('single nanotip') for dielectrophoretic (DEP) concentration of viral particles. The numerical computation studies the concentration efficiency of viral particles ranging from 25 to 100 nm in radius for both nanotips. With DEP and Brownian motion considered, when the particle radius decreases by two times, the concentration time for both nanotips increases by 4-5 times. In the computational study, a dendritic nanotip shows about 1.5 times faster concentration than a single nanotip for the viral particles because the dendritic structure increases the DEP-effective area to overcome the Brownian motion. For the qualitative support of the numerical results, the comparison experiment of a dendritic nanotip and a single nanotip is conducted. Under 1 min of concentration time, a dendritic nanotip shows a higher sensitivity than a single nanotip. When the concentration time is 5 min, the sensitivity of a dendritic nanotip for T7 phage is 10(4) particles ml(-1). The dendritic nanotip-based concentrator has the potential for rapid identification of viral particles.


Assuntos
Eletricidade , Nanotecnologia/métodos , Tamanho da Partícula , Vírion/química , Bacteriófago T7/ultraestrutura , Simulação por Computador , Análise Numérica Assistida por Computador , Fatores de Tempo , Vírion/ultraestrutura
10.
J Clin Microbiol ; 50(11): 3575-80, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22933596

RESUMO

Successful long-term preservation of Mycobacterium tuberculosis cells is important for sample transport, research, biobanking, and the development of new drugs, vaccines, biomarkers, and diagnostics. In this report, Mycobacterium bovis bacillus Calmette-Guérin and M. tuberculosis H37Ra were used as models of M. tuberculosis complex strains to study cryopreservation of M. tuberculosis complex cells in diverse sample matrices at different cooling rates. Cells were cryopreserved in diverse sample matrices, namely, phosphate-buffered saline (PBS), Middlebrook 7H9 medium with or without added glycerol, and human sputum. The efficacy of cryopreservation was quantified by microbiological culture and microscopy with BacLight LIVE/DEAD staining. In all sample matrices examined, the microbiological culture results showed that the cooling rate was the most critical factor influencing cell viability. Slow cooling (a few degrees Celsius per minute) resulted in much higher M. tuberculosis complex recovery rates than rapid cooling (direct immersion in liquid nitrogen) (P < 0.05). Among the three defined cryopreservation media (PBS, 7H9, and 7H9 plus glycerol), there was no significant differential effect on viability (P = 0.06 to 0.87). Preincubation of thawed M. tuberculosis complex cells in 7H9 broth for 20 h before culture on solid Middlebrook 7H10 plates did not help the recovery of the cells from cryoinjury (P = 0.14 to 0.71). The BacLight LIVE/DEAD staining kit, based on Syto 9 and propidium iodide (PI), was also applied to assess cell envelope integrity after cryopreservation. Using the kit, similar percentages of "live" cells with intact envelopes were observed for samples cryopreserved under different conditions, which was inconsistent with the microbiological culture results. This implies that suboptimal cryopreservation might not cause severe damage to the cell wall and/or membrane but instead cause intracellular injury, which leads to the loss of cell viability.


Assuntos
Criopreservação/métodos , Viabilidade Microbiana/efeitos da radiação , Mycobacterium bovis/fisiologia , Mycobacterium bovis/efeitos da radiação , Mycobacterium tuberculosis/fisiologia , Mycobacterium tuberculosis/efeitos da radiação , Contagem de Colônia Microbiana , Meios de Cultura/química , Microscopia , Coloração e Rotulagem
11.
Nanotechnology ; 23(48): 485707, 2012 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-23137928

RESUMO

Electric field-induced concentration has the potential for application in highly sensitive detection of nanoparticles (NPs) for disease diagnosis and drug discovery. Conventional two-dimensional planar electrodes, however, have shown limited sensitivity in NP concentration. In this paper, the dielectrophoretic (DEP) concentration of low-abundance NPs is studied using a nanostructured tip where a high electric field of 3 × 10(7) V m(-1) is generated. In experimental studies, individual 2, 10, and 100 nm Au NPs are concentrated to a nanotip using DEP concentration and are detected by scanning transmission and scanning electron microscopes. The DEP force on Au NPs near the end of a nanotip is computed according to the distance, and then compared with Brownian motion-induced force. The computational study shows qualitative agreement with the experimental results. When the experimental conditions for DEP concentration are optimized for 8 nm-long oligonucleotides, the sensitivity of a nanotip is 10 aM (10 attomolar; nine copies in a 1.5 µl sample volume). This DEP concentrator using a nanotip can be used for molecular detection without amplification.


Assuntos
Ouro/química , Nanopartículas/análise , Nanoestruturas/química , Nanotecnologia/instrumentação , Oligonucleotídeos/isolamento & purificação , Eletricidade , Eletrodos , Nanopartículas/ultraestrutura , Tamanho da Partícula
12.
Sensors (Basel) ; 12(5): 5725-51, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22778610

RESUMO

Various nanowire or nanotube-based devices have been demonstrated to fulfill the anticipated future demands on sensors. To fabricate such devices, electric field-based methods have demonstrated a great potential to integrate one-dimensional nanostructures into various forms. This review paper discusses theoretical and experimental aspects of the working principles, the assembled structures, and the unique functions associated with electric field-based assembly. The challenges and opportunities of the assembly methods are addressed in conjunction with future directions toward high performance sensors.

13.
J Plast Reconstr Aesthet Surg ; 75(4): 1408-1416, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-34952807

RESUMO

The study investigated the osteogenic capacity of a prefabricated periosteal flap created using only skeletonized pedicle transfer without fascia or muscle for vascular induction in rabbit calvarium. A critical-sized bone defect was made in the parietal bone centered on the sagittal suture, and the demineralized bone matrix was implanted. The periosteofascia over the defect was used as a form of prefabricated periosteofascial flap (PPF group, N=10), conventional periosteofascial flap (CPF group, N=10), and nonvascularized free periosteofascial graft (FPG group, N=6). The prefabricated flap was designed via vascular induction by transferring the central artery and vein of the right auricle onto the periosteofascia for 4 weeks prior to flap elevation. A quantitative comparison of volume restoration and radiodensity in the bone defect and a histological study were performed after 6 weeks of covering the bone defect with periosteofascia. The volume restoration of the bone defect covered with the PPF (43.4%) was not different from that of the CPF (46.2%), but significantly increased compared with that of the FPG (24.6%). The radiodensity of the bone defect covered with the PPF (-186.3 HU) was not different from that of the CPF (-153.6 HU), but significantly increased compared with that of the FPG (-329.8 HU). The results were based on adequate vascular development of the periosteum and were closely related to the osteogenic changes in the implanted demineralized bone matrix (DBM). In conclusion, even in the PPF created by transferring only skeletonized vascular pedicles, the osteogenic capacity of the periosteofascial flap is well maintained.


Assuntos
Microcirurgia , Retalhos Cirúrgicos , Animais , Humanos , Microcirurgia/métodos , Osteogênese , Periósteo/transplante , Coelhos , Crânio , Retalhos Cirúrgicos/irrigação sanguínea
14.
Biosens Bioelectron ; 197: 113786, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34801797

RESUMO

Rapid and accurate clinical assessment of hemostasis is essential for managing patients who undergo invasive procedures, experience hemorrhages, or receive antithrombotic therapies. Hemostasis encompasses an ensemble of interactions between the cellular and non-cellular blood components, but current devices assess only partial aspects of this complex process. In this work, we describe the development of a new approach to simultaneously evaluate coagulation function, platelet count or function, and hematocrit using a carbon nanotube-paper composite (CPC) capacitance sensor. CPC capacitance response to blood clotting at 1.3 MHz provided three sensing parameters with distinctive sensitivities towards multiple clotting elements. Whole blood-based hemostasis assessments were conducted to demonstrate the potential utility of the developed sensor for various hemostatic conditions, including pathological conditions, such as hemophilia and thrombocytopenia. Results showed good agreements when compared to a conventional thromboelastography. Overall, the presented CPC capacitance sensor is a promising new biomedical device for convenient non-contact whole-blood based comprehensive hemostasis evaluation.


Assuntos
Técnicas Biossensoriais , Transtornos da Coagulação Sanguínea , Nanotubos de Carbono , Coagulação Sanguínea , Hemostasia , Humanos
15.
Biosensors (Basel) ; 12(3)2022 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-35323418

RESUMO

Current point-of-care (POC) screening of Coronavirus disease 2019 (COVID-19) requires further improvements to achieve highly sensitive, rapid, and inexpensive detection. Here we describe an immunoresistive sensor on a polyethylene terephthalate (PET) film for simple, inexpensive, and highly sensitive COVID-19 screening. The sensor is composed of single-walled carbon nanotubes (SWCNTs) functionalized with monoclonal antibodies that bind to the spike protein of SARS-CoV-2. Silver electrodes are silkscreen-printed on SWCNTs to reduce contact resistance. We determine the SARS-CoV-2 status via the resistance ratio of control- and SARS-CoV-2 sensor electrodes. A combined measurement of two adjacent sensors enhances the sensitivity and specificity of the detection protocol. The lower limit of detection (LLD) of the SWCNT assay is 350 genome equivalents/mL. The developed SWCNT sensor shows 100% sensitivity and 90% specificity in clinical sample testing. Further, our device adds benefits of a small form factor, simple operation, low power requirement, and low assay cost. This highly sensitive film sensor will facilitate rapid COVID-19 screening and expedite the development of POC screening platforms.


Assuntos
Técnicas Biossensoriais , COVID-19 , Nanotubos de Carbono , Técnicas Biossensoriais/métodos , COVID-19/diagnóstico , Humanos , Limite de Detecção , Sistemas Automatizados de Assistência Junto ao Leito , SARS-CoV-2
16.
Lab Chip ; 10(22): 3178-81, 2010 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-20862443

RESUMO

Rapid, low cost screening of tuberculosis requires an effective enrichment method of Mycobacterium tuberculosis (MTB) cells. Currently, microfiltration and centrifugation steps are frequently used for sample preparation, which are cumbersome and time-consuming. In this study, the size-selective capturing mechanism of a microtip-sensor is presented to directly enrich MTB cells from a sample mixture. When a microtip is withdrawn from a spherical suspension in the radial direction, the cells that are concentrated by AC electroosmosis are selectively enriched to the tip due to capillary- and viscous forces. The size-selectivity is characterized by using polystyrene microspheres, which is then applied to size-selective capture of MTB from a sample mixture. Our approach yields a detection limit of 800 cells mL(-1), one of the highest-sensitivity immunosensors to date.


Assuntos
Separação Celular/métodos , Mycobacterium tuberculosis/isolamento & purificação , Animais , Técnicas Bacteriológicas , Linhagem Celular , Separação Celular/instrumentação , Drosophila/citologia , Imunofluorescência/métodos , Microscopia Eletrônica de Varredura , Microesferas , Mycobacterium tuberculosis/citologia , Tamanho da Partícula , Poliestirenos , Sensibilidade e Especificidade , Tuberculose/diagnóstico , Tuberculose/microbiologia , Viscosidade
17.
J Spinal Disord Tech ; 23(6): 377-82, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20124917

RESUMO

STUDY DESIGN: Restrospective case series. OBJECTIVE: To determine changes in the end vertebra and neutral vertebra, and in the magnitudes of coronal and rotational deformities according to position and anesthesia in patients with adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Although it is known that coronal deformity of scoliosis has a tendency to decrease by position and anesthesia, there have been few reports on the effects of position and anesthesia on the rotational deformity of scoliosis. End vertebra and neutral vertebra can change after positioning and anesthesia, but little is known about it. METHODS: Sixty-two structural curves in 31 patients were evaluated using standing, supine, side bending, postanesthesia, and postoperative anteroposterior plain radiographs. Cobb angles and rotation angles by Perdriolle torsionmeter were measured, and the end vertebra and neutral vertebra were identified in each radiograph. RESULTS: Coronal Cobb angles decreased significantly with the correction rates of 25.0%, 31.7%, 59.5%, and 74.0%, and rotational deformities decreased with the correction rates of 6.1%, 24.5%, 6.2%, and 25.7% by supine position, anesthesia, side bending, and surgery, respectively. The end vertebrae changed in 18 patients (58.1%) in both supine and postanesthesia radiographs, and the neutral vertebrae changed in 10 patients (32.3%) in supine radiographs and in 20 patients (64.5%) in postanesthesia radiographs. CONCLUSIONS: Coronal deformities are significantly corrected by supine position and anesthesia. Anesthesia significantly corrects axial rotation, but further correction cannot be achieved by rod derotation. The end vertebra and neutral vertebra have a tendency to vary by position and anesthesia, which gives rise to confusion in the determination of fusion levels.


Assuntos
Anestesia/métodos , Posicionamento do Paciente , Escoliose/cirurgia , Fusão Vertebral/métodos , Adolescente , Adulto , Criança , Feminino , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/cirurgia , Masculino , Radiografia , Estudos Retrospectivos , Escoliose/diagnóstico por imagem , Vértebras Torácicas/diagnóstico por imagem , Vértebras Torácicas/cirurgia , Resultado do Tratamento
18.
Lab Chip ; 9(3): 449-55, 2009 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-19156295

RESUMO

One of the critical challenges in nanostructured biosensors is to manufacture an addressable array of nanopatterns at low cost. The addressable array (1) provides multiplexing for biomolecule detection and (2) enables direct detection of biomolecules without labeling and amplification. To fabricate such an array of nanostructures, current nanolithography methods are limited by the lack of either high throughput or high resolution. This paper presents a high-resolution and high-throughput nanolithography method using the compensated shadow effect in high-vacuum evaporation. The approach enables the fabrication of uniform nanogaps down to 20 nm in width across a 100 mm silicon wafer. The nanogap pattern is used as a template for the routine fabrication of zero-, one-, and two-dimensional nanostructures with a high yield. The method can facilitate the fabrication of nanostructured biosensors on a wafer scale at a low manufacturing cost.


Assuntos
Técnicas Biossensoriais/instrumentação , Dispositivos Lab-On-A-Chip , Nanoestruturas , Nanotecnologia , Algoritmos , Técnicas Biossensoriais/economia , Análise de Fourier , Procedimentos Analíticos em Microchip/economia , Nanoestruturas/química , Nanoestruturas/economia , Silício/química
19.
Lab Chip ; 9(11): 1561-6, 2009 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-19458863

RESUMO

This paper presents a bio-mimetic microfluidic device that mimics the high compliance and the beating frequency of biological cilia in order to achieve bio-compatible manipulation of microfluidics. Because the highly compliant cilia can easily collapse due to interaction energy and surface tension, the major challenge in developing a bio-mimetic device is the manufacturing of highly compliant cilia. An underwater fabrication method is developed to avoid the cilia collapse by lowering the surface energy of the cilia. Another challenge is to mimic the low beating frequency (10-100 Hz) of biological cilia. The proposed microfluidic device is excited by a piezo actuator to resonate the cilia in water. Due to the highly compliant nature of the silicone cilia, the resulting actuation frequency is in the beating frequency range of biological cilia. Simulations and experiments are presented to demonstrate microfluidic manipulation by resonance of the assembled cilia array.


Assuntos
Materiais Biomiméticos/química , Cílios , Técnicas Analíticas Microfluídicas/instrumentação , Silicones/química , Simulação por Computador , Dimetilpolisiloxanos/química , Módulo de Elasticidade , Desenho de Equipamento , Microesferas , Vibração , Água
20.
J Phys Chem B ; 113(31): 10849-58, 2009 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-19591504

RESUMO

One of the critical challenges in the fields of disease diagnostics and environmental monitoring is to concentrate extracellular DNA from a sample mixture rapidly. Unlike genomic DNA in normal cells, extracellular DNA dissolved in a biological sample can potentially offer crucial information about pathogens and toxins. The current concentration methods, however, are not able to directly concentrate extracellular DNA due to aggressive sample preparation steps. This paper presents a concentration mechanism of extracellular DNA onto a nanostructured tip using dielectrophoresis (DEP) in conjunction with capillary action. DNA immersed in a solution is captured onto a nanotip by two sequential actions: (1) attraction of DNA and other bioparticles in the vicinity of a nanotip by DEP and (2) size-specific capture of DNA onto the nanotip by capillary action. To investigate the size-specific capturing mechanism, an analytical model for the capillary action on a nanotip is presented, which is compared to the experiment for capturing polystyrene nanospheres. This analysis predicts the capture of a spherical particle smaller than 0.39 times a nanotip diameter, whereas our experiment shows that polystyrene spheres smaller than 0.84 times a nanotip diameter are captured. This discrepancy can be caused by the increase of the capturing force due to attractive DEP force. In addition, the diameter of the captured spheres can be increased by other experimental conditions including the tip geometry, the multiple particle interaction, and the contact angles. When a nanotip is used for concentrating lambda-DNA, 6.7 pg/mL (210 aM) of DNA is selectively extracted from a sample mixture containing lambda-DNA and Drosophila cells in one minute. The captured DNA is investigated by fluorescence microscopy, scanning electron microscopy (SEM), and X-ray analysis. This nanotip-based DNA concentrating method is a rapid and highly sensitive technique to detect extracellular DNA from a sample mixture.


Assuntos
DNA/isolamento & purificação , Eletroforese/métodos , Nanosferas , Nanotecnologia/instrumentação , Animais , Drosophila/citologia , Eletroforese/instrumentação , Desenho de Equipamento , Tamanho da Partícula
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA