Yi-Shiuan Wu

Continuous affinity-gradient nano-stationary phase served as a column for reversed-phase electrochromatography and matrix carrier in time-of-flight mass spectrometry for protein analysis

This study developed an affinity-gradient nano-stationary phase (AG-NSP) for protein analysis using nanofluidic capillary electrochromatography (nano-CEC) conjugated with matrix assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). The AG-NSP can be used for protein pre-separation in nano-CEC and as a matrix carrier for protein analysis in MALDI-TOF-MS. A hydrophobicity gradient in AG-NSP was photochemically formed by grafting 4-azidoaniline hydrochloride on vertically arrayed multi-wall carbon nanotubes (MWCNTs) through gray-level exposure to UV light. The reversed-phase gradient stationary phase in AG-NSP was tailored according to the properties of the mobile phase gradient in capillary electrochromatography. As a result, the operation of the system is easily automated using a single buffer solution without the need for multiple solvents for elution. The use of nano-CEC with AG-NSP demonstrated excellent separation efficiency and high resolution for various types of DNA/protein/peptide. MALDI-TOF-MS analysis was then performed directly on the separated proteins and peptides on the chip. The proposed system was then used for the detection of three types of proteins with different molecular weights and PI values, including Cytochrome c (12,360, pI = 10), Lysozyme (14,300, pI = 11), and BSA (86,000, pI = 5)), and digested IgG fragments. The proposed system provided resolution of 1000 Da for the proteins in this study and the separation of digested IgG fragments at a low concentration of 1.2 pmol μL(-1).

Cascaded nano-porous silicon for high sensitive biosensing and functional group distinguishing by Mid-IR spectra

We present a chemical-biosensor in the Mid-IR range and based on cascaded porous silicon made on p- and n-type (100) silicon substrates of resistivities between 0.001Ωcm and 0.005Ωcm. The stacked porous layers of various porosities (20-80%) and thicknesses (5-9μm) are formed by successive electrochemical etchings with different current densities. Working with FTIR technique that possesses fast response, high sensitivity, and capability of detecting and identifying functional groups, the cascaded porous structures provided enhanced refractive index sensitivities and reduced detection limits in chemical and biodetection. The largest wavenumber shifts were 50cm(-1)/mM obtained for d-(+)-glucose and 96cm(-1)/μg/mL for Cy5-conjungated Rabbit Anti-Mouse IgG. The lowest detectable concentration of glucose was 80μM (1.4mg/mL) with PS porosity of 40% and thickness of about 9μm while it was 40ng/mL for Cy5-conjugated Rabbit Anti-Mouse IgG which is 2.5×10(5) folds better than those in literature.

Charge-selective gate of arrayed MWCNTs for ultra high-efficient biomolecule enrichment by nano-electrostatic sieving (NES)

We report a rapid and highly-efficient biomolecule preconcentrating device based on nano-electrostatic sieving (NES) mechanism that is facilitated by multi-nanofluidic channels operated in parallel. The opening of these nanochannels is regulated by tunable charges that are generated on arrayed multi-walled carbon nanotubes (MWCNTs) gate. The NES device is fabricated by standard photolithography and plasma-enhanced chemical vapor deposition (PECVD) techniques, followed by subsequent deposition of parylene (poly(p-xylylene))-C on vertically grown MWCNTs in order to obtain arrayed multi-nanochannels with mean pore sizes that are comparable to the thickness of an electrical double layer (EDL). The enrichment efficiency for charged analytes is dependent on electrostatic repulsion, which is regulated by the distribution of the local electric field on the MWCNTs gate. The NES device exhibits polarity selectivity on the analytes and performs efficient collection and separation of biomolecules by probing the surface charge density dependence on the applied gate field. A tunable gate of the parylene-MWCNT nanochannels was used as size sieving devices for nano-scale biomolecules. The experimental results for the collection of FITC-labeled bovine serum albumin (BSA, 0.033nM) were as high as nearly 10(6) fold after only 45min. These data are attributed to the in-parallel molecule sieving process as conducted by the many nanochannels formed among the MWCNTs. This device allows uncharged polar molecules, such as water, to rapidly pass through thus enable highly efficient bio-molecule concentration for the application to ultra-high sensitive biosensing.

High Performance Nanocatalysts Supported on Micro/Nano Carbon Structures Using Ethanol Immersion Pretreatment for Micro DMFCs

In this paper, highly dense platinum (Pt) nanocatalysts were successfully deposited on the hydrophilically-treated nano/micro carbon supports with an ethanol (EtOH) immersion pretreatment and an acidic treatment for the performance improvement of methanol oxidation reaction (MOR). In order to thoroughly immerse the three-dimensional, interwoven structures of the carbon cloth fibers with a 6 M sulfuric acid surface modification, which increasing more oxygen-containing functional groups on the surfaces of the carbon supports, the EtOH immersion pretreatment of the carbon supports was utilized prior to the sulfuric acid treatment. Subsequently, Pt catalysts were reduced on the modified carbon supports by a homemade open-loop reduction system (OLRS) [1] For comparisons, carbon cloth (CC) and carbon nanotube on CC (CNT/CC) supports were employed with and without EtOH immersion pretreatments before Pt catalyst reduction. In the cyclic voltammetry (CV) curves, the electrosorption charges of hydrogen ion (QH) and the peak current density (IP) of the fabricated Pt/CC and Pt/CNT/CC electrodes with the EtOH immersion pretreatments can efficiently be enhanced due to more active Pt sites for electrocatalytic reactions.

Micro and nano structured reaction device for micro DMFC

This paper proposes a novel reaction device design for micro direct methanol fuel cell (muDMFC) with the combination of micro and nano structures for the enhancement of reaction area. The device combined micro porous Si thin film by DRIE with the growth of high-aspect-ratio carbon nanotubes (CNTs) with specific direction on the vertical sidewall surfaces of micro holes to increase the reaction area by 3-4 orders. By the loading of Pt nanoparticles on CNTs, this device would be applied to the anode or cathode in muDMFC. SEM clearly showed well controlled 100~150-mum-deep micro holes with CNTs growth on the sidewall with the diameter of 80~100 nm and length of 3~5 mum. It is suggested that the reaction performance can be improved by orders of magnitude when both the micro structures and CNTs combine together.

Design and fabrication of fuel-self-propelled reaction device for passive micro direct methanol fuel cell anodes

In this paper, we successfully developed a fuel-self-propelled reaction device without consuming any external source of energy for passive micro direct methanol fuel cell (μDMFC) anodes by using the physical phenomenon of surface tension through three-type micro fluidic structures. Firstly, to prevent the backflow of fuel from the reaction zone due to generated gas pressure, highly dense micro-channels were arranged for fuel self-feeding. Interlaced V-shaped micro ribs were then arranged across the reaction zone to rapidly and uniformly distribute fuel into the reaction chambers. Lastly, in the reaction chambers, we combined micro and nano structures as platinum (Pt) catalyst support both to increase the reaction surface area and to remove the gas exhaust [1] for the performance enhancement of micro DMFCs.

Enhancement of catalytic efficiency by partial replacement of ruthenium with platinum nanoparticles for direct methanol fuel cell

In this paper, an open-loop reduction system (OLRS) [1] is employed to produce the core-shell Pt (platinum)/Ru (ruthenium) catalysts on the carbon nanotube/carbon fiber supports (CNT/CF) for direct methanol fuel cell (DMFC) application. By adjusting pH value of the ionized reduction environment, Pt4+ can be first converted into Pt2+ to allow partial Ru replacement with Pt by redox transmetalation and produce Pt/Ru core-shell nano structures [2,3]. Methanol oxidation efficiency and carbon monoxide (CO) poisoning tolerance of the prepared core-shell nano catalysts can be greatly enhanced by our developed OLRS compared to conventional reflux system [4].

Uniform Nafion ® coated HRA anode for high performance micro DMFC

This paper proposes a high reaction area (HRA) electrode with finely dispersed electrocatalysts supported on carbon nanotubes (CNTs) for high performance micro direct methanol fuel cell (μDMFC). Ionomer Nafion^® loading by spin-coating on the catalysts was in-detail investigated for performance enhancement in anodic half-cell. In terms of electrochemical surface area (ESA) and charge transfer resistance (R<inf>CT</inf>), the ionomer-coated Pt/CNTs/Si-based plate electrode at 4000rpm (ESA: 32.37m²/g<inf>Pt</inf>, R<inf>CT</inf>: 19Ωcm²) is demonstrated superior than the best performed electrocatalysts in previous studies (ESA: 25∼35m²/g<inf>Pt</inf>, R<inf>CT</inf>: 35∼60Ωcm²), providing enhanced catalytic activity and much faster charge transfer rate during the methanol electro-oxidation.

High efficient nanocatalysts synthesis by a semi-reflux chemical reduction system

Pt is one of the most employed catalysts for methanol catalysis in direct methanol fuel cell (DMFC). In this study, carbon nanotube (CNT) surface was used for catalyst reduction. By using ethylene glycol as a reducing agent, Pt catalyst precursor (H2PtCl6 · 6H2O) was reduced on the CNTs by a novel method called semi-reflux chemical reduction system (SRCRS). The SRCRS can effectively reduce the catalyst preparation time and the catalyst distribution density can also be much increased by adjusting the pH value. Cyclic voltammetry (CV) and ICP-MS results were used for electrochemical surface area (ECA) calculation. The ECA result was comparable to that of commercial available Pt.

Toward the detection of single cell releasing through high efficient chip-based nano fluidic systems

By enhancing the speed, accuracy, and sensitivity, it opens up a new possibility for direct analysis of biologically relevant entities such as nucleic acids and proteins in single cell level. Nanofluidic systems with critical dimensions which were comparable to the molecular scales can provide the aforementioned performance, offering a novel basis for ultrasensitive and high-resolution bio-detections and medical diagnostics. Inspired by this concept, a nanofluidic system, integrated with a novel multi-nanocahnnel filter, an electrokinetic nano-preconcentrator, and a nanofluidic DAEKF detector for the detection of single cell releasing, is developed. A diluted solution of culture medium from PC-12 cells excited with excess nicotine concentration was detected with near single cell level amounts (c.a. 3000–10000 molecules) in this system after all processing in 20 min. Results showed that this multi-depth micro/nanofluidic chip exhibits superior sensitivity, efficiency, reliability, and reproducibility than those of conventional microchip electrophoresis /electrochromatography systems.