Wanxin Sun - Academia.edu (original) (raw)

Papers by Wanxin Sun

Tissue Engineering, Jul 1, 2007

Three-dimensional (3D) hepatocyte spheroids mimicking the structural and functional characteristi... more Three-dimensional (3D) hepatocyte spheroids mimicking the structural and functional characteristics of hepatocytes in vivo were self-assembled onto a galactosylated polyethylene terephthalate (PET) substratum, and the dynamic process of spheroid formation was investigated using time-lapse confocal microscopy. Hepatocytes cultured on this galactosylated substratum formed small cell-aggregates within 12 h, which gradually merged into "island-like" clusters at approximately 1 day and spread to form prespheroid monolayer within 2 days; the prespheroid monolayer was stretched to fold into compact and larger 3D spheroids after 3 days. We compared the expressions of F-actin (cytoskeleton), phosphorylated focal adhesion kinase (p-FAK, cell-substratum interactions) and E-cadherin (cell-cell interactions) during the dynamic process of 3D hepatocyte spheroid formation with the dynamic process of 2D hepatocyte monolayer formation on collagen substratum. Hepatocytes in the prespheroid monolayer stage exhibited the strongest cell-substratum interactions of all 4 stages during spheroid formation with cell-cell interactions and F-actin distribution comparable with those of the 3D hepatocyte spheroids. The prespheroid monolayer also exhibited better hepatocyte polarity (multidrug resistance protein 2) and tight junction (zonula occludens-1) formation, more-differentiated hepatocyte functions (albumin production and cytochrome P450 1 A activity), and higher sensitivity to hepatotoxicity than the conventional 2D hepatocyte monolayer. The transient prespheroid 3D monolayer could be stabilized on a hybrid glycine-arginine-glycine-aspartic acid-serine (GRGDS)/galactose-PET substratum for up to 1 week and destabilized to form 3D spheroids in excess soluble GRGDS peptide.

Small, 2020

With rising global concerns over the alarming levels of particulate pollution, a sustainable air ... more With rising global concerns over the alarming levels of particulate pollution, a sustainable air quality management is the need of the hour. Air filtration research has gained momentum in recent years. However, the research perspective is still blinkered toward formulating new fiber systems for the energy-intensive electrospinning process to fabricate high quality factor air filters. A holistic approach on sustainable air filtration models is still lacking. The air filter model presented in this work uses a simple process involving water-induced self-organization and self-regeneration of nanofibers, and an easy recycling route after the filter life that not only facilitates reuse of the microfibrous scaffold holding the nanofibers but also allows renewal of nanofibers. Three generations of air filters are fabricated and tested, all having high particulate matter (PM)-adsorbing tendency, high filtration efficiency (>95%), and high Young's modulus (≈5 GPa). The renewable air filters offer a sustainable alternative to the present cost-intensive electrospun air filters.

Review of Scientific Instruments, 2002

Tip characteristics play an important role in the resolution and sensitivity of scanning probe mi... more Tip characteristics play an important role in the resolution and sensitivity of scanning probe microscopy. Extensive efforts have been devoted to tip fabrication. Most of the research is focused on scanning tunneling microscopy applications, which require sharp and short tips. Long tips that can be bent into cantilevered tips have great potential in atomic force microscopy/apertureless near-field scanning optical microscopy applications. However, the fabrication of such tips has been rarely reported. The present work is carried out with the aim of optimizing the conditions suitable for fabricating long and sharp tungsten tips. Besides topography, optical, and spectroscopic information, electrical and magnetic measurements can also be carried out with such tips obtained with the recipe reported in this article. The long tips also make it possible to measure deep grooves/trenches.

Journal of the Optical Society of America A, 2003

Owing to their promise of obtaining optical as well as topographic information in nanometer scale... more Owing to their promise of obtaining optical as well as topographic information in nanometer scale, apertureless near-field scanning optical microscopy (NSOM) and apertureless near-field scanning optical spectroscopy have drawn much attention recently. However, NSOM is still not a mature technique. A proper understanding of and the ability to tune the near field around the tip end is critically important in NSOM instrumentation and in NSOM image interpretation. On the basis of reflection geometry, we systematically studied the effects of a number of parameters pertinent in the application of apertureless NSOM, e.g., polarization, incident angle, wavelength of the incident laser, tip material, and tip length, by using the generalized field propagator technique. Our results show that all the above parameters have a significant influence on near-field enhancement and that care must be taken in the design of the experiment in order to maximize the near field. In addition to apertureless NSOM and spectroscopy, apertureless near-field lithography can benefit from these simulation results.

Journal of Raman Spectroscopy, 2003

ABSTRACT

Journal of Applied Physics, 2004

Amorphous boron nitride (a-BN) was produced by ball milling of hexagonal BN (h-BN). Turbostratic ... more Amorphous boron nitride (a-BN) was produced by ball milling of hexagonal BN (h-BN). Turbostratic BN (t-BN) and mesographite BN (m-BN) with different degrees of three-dimensional order (DTDO) were subsequently prepared by annealing the a-BN at different temperatures. The photoluminescence (PL) of the BN samples with different structures and DTDOs was investigated in the visible region from 460 to 800nm. The h-, a-, and t-BN samples, which have completely ordered, disordered and two-dimensionally ordered structures, respectively, emitted weak continuums. The m-BN samples with three-dimensionally ordered structures gave discrete PL bands, which we attributed to the presence of NB antisites or a complex formed by an Fe atom and a B vacancy in the BN layer. The intensity and energy of the PL bands changed greatly with DTDO and could be tuned by varying the annealing temperature. The strongest PL bands at 593 and 612nm were observed in one of the m-BN samples produced at an annealing temp...

JOSA A, 2003

Owing to their promise of obtaining optical as well as topographic information in nanometer scale... more Owing to their promise of obtaining optical as well as topographic information in nanometer scale, apertureless near-field scanning optical microscopy (NSOM) and apertureless near-field scanning optical spectroscopy have drawn much attention recently. However, NSOM ...

Journal of Biophotonics, Jan 19, 2015

Cancer initiating cells (CICs) have been the focus of recent anti-cancer therapies, exhibiting st... more Cancer initiating cells (CICs) have been the focus of recent anti-cancer therapies, exhibiting strong invasion capability via potentially enhanced ability to remodel extracellular matrices (ECM). We

Coatings, Jan 21, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Eco-friendly and bio-degradable lubricants and additives have gained tremendous attention in rece... more Eco-friendly and bio-degradable lubricants and additives have gained tremendous attention in recent years due to sustainability awareness. Implementing green solutions for oil and lubricants has become mandatory due to high regulatory controls. To meet these requirements, extensive tribology tests are needed. Tribology tests usually need to mimic real situations in terms of load, speed and lubrication. However, current tribology tools are designed for a specific experiment only such as four-ball testing for lubricant; making it difficult for Tribologists to assess different aspects of an object under scrutiny without multiple testing tools. Other drawbacks include low usage of each tool, waste of lab space, tests cannot be done on the same location or same material, making it difficult to correlate different properties which is critical in understanding the mechanism behind. In this article, we report the development of a versatile testing platform which covers most standard tests r...

Sensorized actuators are critical to imitate proprio-/exteroception properties of biological neur... more Sensorized actuators are critical to imitate proprio-/exteroception properties of biological neuromuscular systems. Existing add-on approaches, which physically blend heterogeneous sensor/actuator components, fall short of yielding satisfactory solutions, considering their suboptimal interfaces, poor adhesion, and electronic/mechanical property mismatch. Here, we report a single homogeneous material comprising seamless sensing-actuation unification properties at nano-/molecule levels, in which built-in sensing functions originate from the actuator architecture itself. In-situ-grown silver nanoparticles and metal-ligand complexes cooperatively create a silver–polymer framework (SPF) that is stretchable (1200%), conductive (0.076 S/m), and strong (0.76 MPa in-strength). SPF displays concomitant multimodal sensing (mechanical and thermal cues) and sensorized actuation capabilities, which include proprio-deformation and external stimuli perceptions (simultaneous with load-lifting abilit...

ACS Applied Materials & Interfaces, 2019

A more accurate solution thermodynamic analysis of colloidal molybdenum disulfide (MoS 2) nanoshe... more A more accurate solution thermodynamic analysis of colloidal molybdenum disulfide (MoS 2) nanosheets dispersed in 91 combinations of organic solvent (alcohols and amines)-water mixtures is made possible by the application of viscosity-and-densitynormalized centrifugation method to the post-sonication stock solution. This centrifugation method accounts the solvent mixture's density and viscosity in order to apply different centrifugation times based on the Stoke's law, and in effect eliminates the kinetic interferences arising from different densities and viscosities of the solvent mixtures used as the dispersing media. This allows us to reveal that the solvent's molecular size and hydrogen-bonding strength are additional important factors that determine the Gibbs

Chemistry of Materials, 2019

Advanced Energy Materials, 2019

Semiartificial photosynthetic systems have opened up new avenues for harvesting solar energy usin... more Semiartificial photosynthetic systems have opened up new avenues for harvesting solar energy using natural photosynthetic materials in combination with synthetic components. This work reports a new, semiartificial system for solar energy conversion that synergistically combines photoreactions in a purple bacterial photosynthetic membrane with those in three types of transition metal–semiconductor Schottky junctions. A transparent film of a common transition metal interfaced with an n‐doped silicon semiconductor exhibits an in‐plane potential gradient when a light‐penetration variance is established on its surface by optical shading of photoabsorbing photosynthetic membranes. The in‐plane potential gradients (0.08–0.3 V) enable a directional charge transport between the synthetic and natural photoelectric systems, which is further enhanced in a device setting by a biocompatible thixotropic gel electrolyte that permeates the membrane multilayer, facilitating a strong and steady photoe...

Journal of biophotonics, Jan 19, 2015

Cancer initiating cells (CICs) have been the focus of recent anti-cancer therapies, exhibiting st... more Cancer initiating cells (CICs) have been the focus of recent anti-cancer therapies, exhibiting strong invasion capability via potentially enhanced ability to remodel extracellular matrices (ECM). We have identified CICs in a human breast cancer cell line, MX-1, and developed a xenograft model in SCID mice. We investigated the CICs' matrix-remodeling effects using Second Harmonic Generation (SHG) microscopy to identify potential phenotypic signatures of the CIC-rich tumors. The isolated CICs exhibit higher proliferation, drug efflux and drug resistant properties in vitro; were more tumorigenic than non-CICs, resulting in more and larger tumors in the xenograft model. The CIC-rich tumors have less collagen in the tumor interior than in the CIC-poor tumors supporting the idea that the CICs can remodel the collagen more effectively. The collagen fibers were preferentially aligned perpendicular to the CIC-rich tumor boundary while parallel to the CIC-poor tumor boundary suggesting mo...

Applied Physics Letters, 2015

We report on a microfluidic system formed by 200 nl water droplets, encapsulated by a 600 nl mine... more We report on a microfluidic system formed by 200 nl water droplets, encapsulated by a 600 nl mineral oil placed on a hydrophobically coated glass microscope cover slip. The micromachined heater underneath the glass was able to heat up the sample at a heating rate of 650 °C/s, heating the water sample up to 200 °C in less than 2 s. The sample/glass and the sample/oil interface did not have nucleation centers, showing that the sample reached a superheated stage without the necessity of being pressurized to suppress boiling. This method can be utilized for various applications currently being conducted in autoclaves.

Ultramicroscopy, 2003

The combination of near-field scanning optical microscopy and Raman spectroscopy provides chemica... more The combination of near-field scanning optical microscopy and Raman spectroscopy provides chemical/structural specific information with nanometer spatial resolution, which are critically important for a wide range of applications, including the study of Si devices, nanodevices, quantum dots, single molecules of biological samples. In this paper, we describe our near-field Raman study using apertureless probes. Our system has two important features, critical to practical applications. (1) The near-field Raman enhancement was achieved by Ag coating of the metal probes, without any preparation of the sample, and (2) while all other apertureless near-field Raman systems were constructed in transmission mode, our system works in the reflection mode, making near-field Raman study a reality for any samples. We have obtained the first 1D Raman mapping of a real Si device with 1 s exposure time. This is a very significant development in near-field scanning Raman microscopy as it is the first demonstration that this technique can be used for imaging purpose because of the short integration time. In addition, the metal tips used in our setup can be utilized to make simultaneous AFM and electrical mappings such as resistance and capacitance that are critical parameters for device applications.

Solid State Communications, 2000

High-energy mechanical milling of spinel NiFe 2 O 4 leads to the formation of a disordered wustit... more High-energy mechanical milling of spinel NiFe 2 O 4 leads to the formation of a disordered wustite-like structure. Cluster glass behavior was found in the Mo Èssbauer study. The investigation suggested ferrimagnetic clusters in an antiferromagnetic matrix. The ferrimagnetic and antiferromagnetic exchange coupling results in a strong uni-directional anisotropy and a coercivity of over 10 kOe after magnetic cooling.

Tissue Engineering, Jul 1, 2007

Three-dimensional (3D) hepatocyte spheroids mimicking the structural and functional characteristi... more Three-dimensional (3D) hepatocyte spheroids mimicking the structural and functional characteristics of hepatocytes in vivo were self-assembled onto a galactosylated polyethylene terephthalate (PET) substratum, and the dynamic process of spheroid formation was investigated using time-lapse confocal microscopy. Hepatocytes cultured on this galactosylated substratum formed small cell-aggregates within 12 h, which gradually merged into "island-like" clusters at approximately 1 day and spread to form prespheroid monolayer within 2 days; the prespheroid monolayer was stretched to fold into compact and larger 3D spheroids after 3 days. We compared the expressions of F-actin (cytoskeleton), phosphorylated focal adhesion kinase (p-FAK, cell-substratum interactions) and E-cadherin (cell-cell interactions) during the dynamic process of 3D hepatocyte spheroid formation with the dynamic process of 2D hepatocyte monolayer formation on collagen substratum. Hepatocytes in the prespheroid monolayer stage exhibited the strongest cell-substratum interactions of all 4 stages during spheroid formation with cell-cell interactions and F-actin distribution comparable with those of the 3D hepatocyte spheroids. The prespheroid monolayer also exhibited better hepatocyte polarity (multidrug resistance protein 2) and tight junction (zonula occludens-1) formation, more-differentiated hepatocyte functions (albumin production and cytochrome P450 1 A activity), and higher sensitivity to hepatotoxicity than the conventional 2D hepatocyte monolayer. The transient prespheroid 3D monolayer could be stabilized on a hybrid glycine-arginine-glycine-aspartic acid-serine (GRGDS)/galactose-PET substratum for up to 1 week and destabilized to form 3D spheroids in excess soluble GRGDS peptide.

Small, 2020

With rising global concerns over the alarming levels of particulate pollution, a sustainable air ... more With rising global concerns over the alarming levels of particulate pollution, a sustainable air quality management is the need of the hour. Air filtration research has gained momentum in recent years. However, the research perspective is still blinkered toward formulating new fiber systems for the energy-intensive electrospinning process to fabricate high quality factor air filters. A holistic approach on sustainable air filtration models is still lacking. The air filter model presented in this work uses a simple process involving water-induced self-organization and self-regeneration of nanofibers, and an easy recycling route after the filter life that not only facilitates reuse of the microfibrous scaffold holding the nanofibers but also allows renewal of nanofibers. Three generations of air filters are fabricated and tested, all having high particulate matter (PM)-adsorbing tendency, high filtration efficiency (>95%), and high Young's modulus (≈5 GPa). The renewable air filters offer a sustainable alternative to the present cost-intensive electrospun air filters.

Review of Scientific Instruments, 2002

Tip characteristics play an important role in the resolution and sensitivity of scanning probe mi... more Tip characteristics play an important role in the resolution and sensitivity of scanning probe microscopy. Extensive efforts have been devoted to tip fabrication. Most of the research is focused on scanning tunneling microscopy applications, which require sharp and short tips. Long tips that can be bent into cantilevered tips have great potential in atomic force microscopy/apertureless near-field scanning optical microscopy applications. However, the fabrication of such tips has been rarely reported. The present work is carried out with the aim of optimizing the conditions suitable for fabricating long and sharp tungsten tips. Besides topography, optical, and spectroscopic information, electrical and magnetic measurements can also be carried out with such tips obtained with the recipe reported in this article. The long tips also make it possible to measure deep grooves/trenches.

Journal of the Optical Society of America A, 2003

Owing to their promise of obtaining optical as well as topographic information in nanometer scale... more Owing to their promise of obtaining optical as well as topographic information in nanometer scale, apertureless near-field scanning optical microscopy (NSOM) and apertureless near-field scanning optical spectroscopy have drawn much attention recently. However, NSOM is still not a mature technique. A proper understanding of and the ability to tune the near field around the tip end is critically important in NSOM instrumentation and in NSOM image interpretation. On the basis of reflection geometry, we systematically studied the effects of a number of parameters pertinent in the application of apertureless NSOM, e.g., polarization, incident angle, wavelength of the incident laser, tip material, and tip length, by using the generalized field propagator technique. Our results show that all the above parameters have a significant influence on near-field enhancement and that care must be taken in the design of the experiment in order to maximize the near field. In addition to apertureless NSOM and spectroscopy, apertureless near-field lithography can benefit from these simulation results.

Journal of Raman Spectroscopy, 2003

ABSTRACT

Journal of Applied Physics, 2004

Amorphous boron nitride (a-BN) was produced by ball milling of hexagonal BN (h-BN). Turbostratic ... more Amorphous boron nitride (a-BN) was produced by ball milling of hexagonal BN (h-BN). Turbostratic BN (t-BN) and mesographite BN (m-BN) with different degrees of three-dimensional order (DTDO) were subsequently prepared by annealing the a-BN at different temperatures. The photoluminescence (PL) of the BN samples with different structures and DTDOs was investigated in the visible region from 460 to 800nm. The h-, a-, and t-BN samples, which have completely ordered, disordered and two-dimensionally ordered structures, respectively, emitted weak continuums. The m-BN samples with three-dimensionally ordered structures gave discrete PL bands, which we attributed to the presence of NB antisites or a complex formed by an Fe atom and a B vacancy in the BN layer. The intensity and energy of the PL bands changed greatly with DTDO and could be tuned by varying the annealing temperature. The strongest PL bands at 593 and 612nm were observed in one of the m-BN samples produced at an annealing temp...

JOSA A, 2003

Owing to their promise of obtaining optical as well as topographic information in nanometer scale... more Owing to their promise of obtaining optical as well as topographic information in nanometer scale, apertureless near-field scanning optical microscopy (NSOM) and apertureless near-field scanning optical spectroscopy have drawn much attention recently. However, NSOM ...

Journal of Biophotonics, Jan 19, 2015

Cancer initiating cells (CICs) have been the focus of recent anti-cancer therapies, exhibiting st... more Cancer initiating cells (CICs) have been the focus of recent anti-cancer therapies, exhibiting strong invasion capability via potentially enhanced ability to remodel extracellular matrices (ECM). We

Coatings, Jan 21, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Eco-friendly and bio-degradable lubricants and additives have gained tremendous attention in rece... more Eco-friendly and bio-degradable lubricants and additives have gained tremendous attention in recent years due to sustainability awareness. Implementing green solutions for oil and lubricants has become mandatory due to high regulatory controls. To meet these requirements, extensive tribology tests are needed. Tribology tests usually need to mimic real situations in terms of load, speed and lubrication. However, current tribology tools are designed for a specific experiment only such as four-ball testing for lubricant; making it difficult for Tribologists to assess different aspects of an object under scrutiny without multiple testing tools. Other drawbacks include low usage of each tool, waste of lab space, tests cannot be done on the same location or same material, making it difficult to correlate different properties which is critical in understanding the mechanism behind. In this article, we report the development of a versatile testing platform which covers most standard tests r...

Sensorized actuators are critical to imitate proprio-/exteroception properties of biological neur... more Sensorized actuators are critical to imitate proprio-/exteroception properties of biological neuromuscular systems. Existing add-on approaches, which physically blend heterogeneous sensor/actuator components, fall short of yielding satisfactory solutions, considering their suboptimal interfaces, poor adhesion, and electronic/mechanical property mismatch. Here, we report a single homogeneous material comprising seamless sensing-actuation unification properties at nano-/molecule levels, in which built-in sensing functions originate from the actuator architecture itself. In-situ-grown silver nanoparticles and metal-ligand complexes cooperatively create a silver–polymer framework (SPF) that is stretchable (1200%), conductive (0.076 S/m), and strong (0.76 MPa in-strength). SPF displays concomitant multimodal sensing (mechanical and thermal cues) and sensorized actuation capabilities, which include proprio-deformation and external stimuli perceptions (simultaneous with load-lifting abilit...

ACS Applied Materials & Interfaces, 2019

A more accurate solution thermodynamic analysis of colloidal molybdenum disulfide (MoS 2) nanoshe... more A more accurate solution thermodynamic analysis of colloidal molybdenum disulfide (MoS 2) nanosheets dispersed in 91 combinations of organic solvent (alcohols and amines)-water mixtures is made possible by the application of viscosity-and-densitynormalized centrifugation method to the post-sonication stock solution. This centrifugation method accounts the solvent mixture's density and viscosity in order to apply different centrifugation times based on the Stoke's law, and in effect eliminates the kinetic interferences arising from different densities and viscosities of the solvent mixtures used as the dispersing media. This allows us to reveal that the solvent's molecular size and hydrogen-bonding strength are additional important factors that determine the Gibbs

Chemistry of Materials, 2019

Advanced Energy Materials, 2019

Semiartificial photosynthetic systems have opened up new avenues for harvesting solar energy usin... more Semiartificial photosynthetic systems have opened up new avenues for harvesting solar energy using natural photosynthetic materials in combination with synthetic components. This work reports a new, semiartificial system for solar energy conversion that synergistically combines photoreactions in a purple bacterial photosynthetic membrane with those in three types of transition metal–semiconductor Schottky junctions. A transparent film of a common transition metal interfaced with an n‐doped silicon semiconductor exhibits an in‐plane potential gradient when a light‐penetration variance is established on its surface by optical shading of photoabsorbing photosynthetic membranes. The in‐plane potential gradients (0.08–0.3 V) enable a directional charge transport between the synthetic and natural photoelectric systems, which is further enhanced in a device setting by a biocompatible thixotropic gel electrolyte that permeates the membrane multilayer, facilitating a strong and steady photoe...

Journal of biophotonics, Jan 19, 2015

Cancer initiating cells (CICs) have been the focus of recent anti-cancer therapies, exhibiting st... more Cancer initiating cells (CICs) have been the focus of recent anti-cancer therapies, exhibiting strong invasion capability via potentially enhanced ability to remodel extracellular matrices (ECM). We have identified CICs in a human breast cancer cell line, MX-1, and developed a xenograft model in SCID mice. We investigated the CICs' matrix-remodeling effects using Second Harmonic Generation (SHG) microscopy to identify potential phenotypic signatures of the CIC-rich tumors. The isolated CICs exhibit higher proliferation, drug efflux and drug resistant properties in vitro; were more tumorigenic than non-CICs, resulting in more and larger tumors in the xenograft model. The CIC-rich tumors have less collagen in the tumor interior than in the CIC-poor tumors supporting the idea that the CICs can remodel the collagen more effectively. The collagen fibers were preferentially aligned perpendicular to the CIC-rich tumor boundary while parallel to the CIC-poor tumor boundary suggesting mo...

Applied Physics Letters, 2015

We report on a microfluidic system formed by 200 nl water droplets, encapsulated by a 600 nl mine... more We report on a microfluidic system formed by 200 nl water droplets, encapsulated by a 600 nl mineral oil placed on a hydrophobically coated glass microscope cover slip. The micromachined heater underneath the glass was able to heat up the sample at a heating rate of 650 °C/s, heating the water sample up to 200 °C in less than 2 s. The sample/glass and the sample/oil interface did not have nucleation centers, showing that the sample reached a superheated stage without the necessity of being pressurized to suppress boiling. This method can be utilized for various applications currently being conducted in autoclaves.

Ultramicroscopy, 2003

The combination of near-field scanning optical microscopy and Raman spectroscopy provides chemica... more The combination of near-field scanning optical microscopy and Raman spectroscopy provides chemical/structural specific information with nanometer spatial resolution, which are critically important for a wide range of applications, including the study of Si devices, nanodevices, quantum dots, single molecules of biological samples. In this paper, we describe our near-field Raman study using apertureless probes. Our system has two important features, critical to practical applications. (1) The near-field Raman enhancement was achieved by Ag coating of the metal probes, without any preparation of the sample, and (2) while all other apertureless near-field Raman systems were constructed in transmission mode, our system works in the reflection mode, making near-field Raman study a reality for any samples. We have obtained the first 1D Raman mapping of a real Si device with 1 s exposure time. This is a very significant development in near-field scanning Raman microscopy as it is the first demonstration that this technique can be used for imaging purpose because of the short integration time. In addition, the metal tips used in our setup can be utilized to make simultaneous AFM and electrical mappings such as resistance and capacitance that are critical parameters for device applications.

Solid State Communications, 2000

High-energy mechanical milling of spinel NiFe 2 O 4 leads to the formation of a disordered wustit... more High-energy mechanical milling of spinel NiFe 2 O 4 leads to the formation of a disordered wustite-like structure. Cluster glass behavior was found in the Mo Èssbauer study. The investigation suggested ferrimagnetic clusters in an antiferromagnetic matrix. The ferrimagnetic and antiferromagnetic exchange coupling results in a strong uni-directional anisotropy and a coercivity of over 10 kOe after magnetic cooling.