Micro-nano Hybrid Research Articles

Dual-Band Modulation of Visible and Near-Infrared Light Transmittance in an All-Solution-Processed Hybrid Micro-Nano Composite Film.

Smart windows with controllable visible and near-infrared light transmittance can significantly improve the building's energy efficiency and inhabitant comfort. However, most of the current smart window technology cannot achieve the target of ideal solar control. Herein, we present a novel all-solution-processed hybrid micronano composite smart material that have four optical states to separately modulate the visible and NIR light transmittance through voltage and temperature, respectively. This dual-band optical modulation was achieved by constructing a phase-separated polymer framework, which contains the microsized liquid crystals domains with a negative dielectric constant and tungsten-doped vanadium dioxide (W-VO2) nanocrystals (NCs). The film with 2.5 wt % W-VO2 NCs exhibits transparency at normal condition, and the passage of visible light can be reversibly and actively regulated between 60.8% and 1.3% by external applied voltage. Also, the transmittance of NIR light can be reversibly and passively modulated between 59.4% and 41.2% by temperature. Besides, the film also features easy all-solution processability, fast electro-optical (E-O) response time, high mechanical strength, and long-term stability. The as-prepared film provides new opportunities for next-generation smart window technology, and the proposed strategy is conductive to engineering novel hybrid inorganic-organic functional matters.

An on-chip polarization splitter based on the radiation loss in the bending hybrid plasmonic waveguide structure

Polarization beam splitters (PBSs) are one of the key components in the integrated photonic circuits. To increase the integration density, various complex hybrid plasmonic structures have been numerically designed to shrink the footprints of the PBSs. Here, to decrease the complexity of the small hybrid structures and the difficulty of the hybrid micro-nano fabrications, the radiation losses are utilized to experimentally demonstrate an ultra-small, broadband, and efficient PBS in a simple bending hybrid plasmonic waveguide structure. The hybrid plasmonic waveguide comprising a dielectric strip on the metal surface supports both the transverse-magnetic (TM) and transverse-electric (TE) waveguide modes. Because of the different field confinements, the TE waveguide mode has larger radiation loss than the TM waveguide mode in the bending hybrid strip waveguide. Based on the different radiation losses, the two incident waveguide modes of orthogonal polarization states are efficiently split in the proposed structure with a footprint of only about 2.2 × 2.2 μm2 on chips. Since there is no resonance or interference in the splitting process, the operation bandwidth is as broad as Δλ = 70 nm. Moreover, the utilization of the strongly confined waveguide modes instead of the bulk free-space light (with the spot size of at least a few wavelengths) as the incident source considerably increases the coupling efficiency, resulting in a low insertion loss of <3 dB.

Tunability of Pd-nanogapped H2 sensors made on SiO2-coated Si micropillar arrays

A micro-nano hybrid technique is implemented to produce Pd-nanogapped gas sensors with tunable H2 sensing properties. The basic idea is to deposit a Pd film on a SiO2-coated Si micropillar array. By adjusting the SiO2-gap size and Pd film thickness, one can tune the size and distribution of the nanogaps in the Pd film precisely to achieve the desired gas sensing performances. With this approach, sensors of three different configurations were fabricated to go through the tests for 0–6% H2 at 40°C. Different sensor types were found to give respective dynamic range of detection, shape of sensor response and mode of operation. The sensor type designed to contain an Au/Cr buffer layer exhibits a detection limit of 20ppm of H2. The method is scalable and compatible with Si-based micromachining processes. The design is also extendable for making multi-sensor arrays. The physical mechanisms involved in controlling the sensor properties are proposed and discussed.

Construction of WO3 coatings with micro-nano hybrid structures by liquid precursor flame spray for enhanced sensing performances to sub-ppm ozone

WO3 coatings with tunable micro-nano hybrid structures were fabricated by liquid precursor flame spraying. The coatings consisting of the sole component of monoclinic WO3 show porous topographical morphology with grains of ∼20nm and pores of ∼4–8μm. Assessment of gas sensing performances of the coatings to ozone reveals their optimum operating temperature of 150°C, and sensor response of 3.9 and 46.7 to ozone concentration of 0.5ppm and 2.0ppm respectively. The results shed light on construction of ceramic coatings with tunable hybrid structures by the precursor flame spray technical route for functional applications.

Progress of electrowetting applications in micro-nano energy conversion and utilization systems

Dynamic wetting is a process that one fluid replaces the other fluid (usually gas) on solid surfaces, which is very common and widely involved in our daily activities and many industrial applications, such as printing, dyeing, coating, drag reduction, and many others. Due to the complexity of the dynamic wetting, most of studies have focused on understanding the dynamic wetting behaviors of simple fluids on homogeneous flat surfaces without any external fields in early ages. The gaps between the research with ideal wetting conditions and real applications facilitate the studies of dynamic wetting with complex conditions, such as complex fluids (non-Newtonian fluids, colloidal solutions, nanofluids etc.), real substrates (hydrophobic surfaces, hydrophilic surfaces, micro-nano hybrid surfaces or others), and complex external fields (electric fields, thermal fields or magnetic fields). Among these studies, the dynamic wetting with external electric fields, also known as electrowetting, is a hot topic. Electrowetting is a modification method of the surface wettability using an applied electric field. Electrowetting has been widely used in many microfluidic systems, such as electronic microlenses, electronic-paper, electrowetting display and others. This paper provides a review on the recent developments of electrowetting applications in the emerging micro-nano energy conversion and utilization systems, ranging from the physical and theoretical research, fundamental applications to industrial applications. The fundamental physical concepts and principles involved in electrowetting phenomena are reviewed in the first part. The mainstream physical mechanisms related to electrowetting are summarized and compared to illustrate their successes and limitations. The challenges in the topic of electrowetting phenomena are summarized, which lie in four aspects: (1) the contact angle saturation; (2) the contact angle hysteresis; (3) the electric puncture & electrolysis; (4) electrowetting reversibility on super-hydrophobic surfaces. This paper also reviews and summarizes the new achievements and contributions on material, structure and complex external conditions related to electrowetting applications. The gaps between electrowetting fundamental research and industrial applications lie in several facts, including the new electrowetting materials with low triggered electric field strength, the novel structures which can easily manipulate the liquid transport using electrowetting. Among the electrowetting structures, the “sandwich” style, the open-style, the twins-style, as well as the pole-array-style are summarized to illustrate their advantages and disadvantages. The liquid manipulation, the complex inner flows and the droplet vibration with external electric fields using electrowetting provide potential applications in the energy conversion or thermal management devices. There have been some pioneering studies on micro-nano energy conversion and utilization systems using electrowetting. The latest development on the research of the applications in the micro-nano energy conversion and utilization systems is reviewed, including micro-channel systems, electronic cooling, phase change and solar photovoltaic system applications. The outlooks on the topic of electrowetting are provided in end of this review, including: (1) new materials and EWOD (electrowetting-on-dielectric) structures; (2) electrowetting of complex fluids containing functional particles; (3) electrowetting coupled with thermal field or magnetic field; (4) enhancing boiling and condensation heat transfer using electrowetting; (5) smart thermal management methods using electrowetting.

A low-cost method of fabricating hybrid micro-nano fluidic chip by double-layer PDMS mold and UV–thermal nanoimprinting

Micro-nano fluidic chips have become important tools in biomedical testing and research, their more frequent and diverse application being hampered mainly by their high cost, reflective of complex and expensive production methods. Our study introduces a simple, cost-effective new procedure whereby a sturdy PDMS mold consisting of two layers of poured PDMS with a photomask film bonded between them is used for replicating a hybrid micro-nano structure on a SU-8 substrate. The bottom surface of the mold receives a pattern of nano-ridges by pouring the first layer of PDMS on a 2D silicon nano-mold obtained by plasma etching after inclined Cu deposition. Using the double-layer PDMS mold, nano-channels can be imprinted with micro-channels cross-linked through the photomask in a single step of UV–thermal imprinting. The advantages of our end product, a chip with 205-μm-wide and 10-μm-deep micro-channels, cross-linked with 158-nm-wide and 90-nm-deep nano-channels, are its high precision and low cost.

Biomedical Applications of Advanced Multifunctional Magnetic Nanoparticles.

In this review, we have presented the latest results and highlights on biomedical applications of a class of noble metal nanoparticles, such as gold, silver and platinum, and a class of magnetic nanoparticles, such as cobalt, nickel and iron. Their most important related compounds are also discussed for biomedical applications for treating various diseases, typically as cancers. At present, both physical and chemical methods have been proved very successful to synthesize, shape, control, and produce metal- and oxide-based homogeneous particle systems, e.g., nanoparticles and microparticles. Therefore, we have mainly focused on functional magnetic nanoparticles for nanomedicine because of their high bioadaptability to the organs inside human body. Here, bioconjugation techniques are very crucial to link nanoparticles with conventional drugs, nanodrugs, biomolecules or polymers for biomedical applications. Biofunctionalization of engineered nanoparticles for biomedicine is shown respective to in vitro and in vivo analysis protocols that typically include drug delivery, hyperthermia therapy, magnetic resonance imaging (MRI), and recent outstanding progress in sweep imaging technique with Fourier transformation (SWIFT) MRI. The latter can be especially applied using magnetic nanoparticles, such as Co-, Fe-, Ni-based nanoparticles, α-Fe2O3, and Fe3O4 oxide nanoparticles for analysis and treatment of malignancies. Therefore, this review focuses on recent results of scientists, and related research on diagnosis and treatment methods of common and dangerous diseases by biomedical engineered nanoparticles. Importantly, nanosysems (nanoparticles) or microsystems (microparticles) or hybrid micronano systems are shortly introduced into nanomedicine. Here, Fe oxide nanoparticles ultimately enable potential and applicable technologies for tumor-targeted imaging and therapy. Finally, we have shown the latest aspects of the most important Fe-based particle systems, such as Fe, α-Fe2O3, Fe3O4, Fe-Fe(x)O(y) oxide core-shell nanoparticles, and CoFe2O4-MnFe2O4 core-shell nanoparticles for nanomedicine in the efficient treatment of large tumors at low cost in near future.

Sb2S3Quantum-Dot Sensitized Solar Cells with Silicon Nanowire Photoelectrode

We propose a novel quantum-dot sensitized solar cell (QDSSC) structure that employs a quantum dot/semiconductor silicon (QD/Si) coaxial nanorod array to replace the conventional dye/TiO2/TCO photoelectrode. We replaced the backlight input mode with top-side illumination and used a quantum dot to replace dye as the light-absorbing material. Photon-excited photoelectrons can be effectively transported to each silicon nanorod and conveyed to the counter electrode. We use two-stage metal-assisted etching (MAE) to fabricate the micro-nano hybrid structure on a silicon substrate. We then use the chemical bath deposition (CBD) method to synthesize a Sb2S3quantum dot on the surface of each silicon nanorod to form the photoelectrode for the quantum dot/semiconductor silicon coaxial nanorod array. We use a xenon lamp to simulate AM 1.5 G (1000 W/m2) sunlight. Then, we investigate the influence of different silicon nanorod arrays and CBD deposition times on the photoelectric conversion efficiency. When an NH (N-type with high resistance) silicon substrate is used, the QD/Si coaxial nanorod array synthesized by three runs of Sb2S3deposition shows the highest photoelectric conversion efficiency of 0.253%. The corresponding short-circuit current density, open-circuit voltage, and fill factor are 5.19 mA/cm2, 0.24 V, and 20.33%, respectively.

Improved fracture toughness and integrated damage sensing capability by spray coated CNTs on carbon fibre prepreg

The development of a hierarchically engineered micro-nano hybrid composite system is described. A spray coating technique has been utilized as an effective way to deposit carbon nanotubes (CNTs) onto carbon fibre prepregs with good control of network formation and the potential for localization. Compared to more traditional approaches of introducing CNTs into epoxy matrices for enhancing composite properties, this technique has benefits in terms of its simplicity and versatility, as well as the potential for industrial scale-up. The effectiveness of the technique is demonstrated by the extremely low CNT loading (0.047wt.%) needed to significantly increase the Mode-I fracture toughness of the carbon fibre laminates by about 50%, which is so far the largest reported improvement for such extremely low concentrations of non-functionalized CNTs. In-situ damage sensing has also been presented for the monitoring of structural health of these nano-engineered composite laminates upon loading, and a systematic analysis of sensing signals is performed.

Preparation of superhydrophobic and transparent micro-nano hybrid coatings from polymethylhydroxysiloxane and silica ormosil aerogels

Abstract Superhydrophobic and transparent polymethylhydroxysiloxane (PMHOS)/silica ormosil aerogel hybrids were prepared successfully by mixing of PMHOS with various weight percentages of silica ormosil aerogels (as synthesized from methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS) precursors) in separate seal perfume glass vials. The hybrids were spin coated on glass substrate at 1000 rpm for 60 seconds and used for further analysis. The surface morphology and chemical compositions of the hybrids were analyzed by high resolution scanning electron microscopy, high resolution transmission electron microscopy, atomic force spectroscopy, adsorption and desorption isotherm, and X-ray photoelectron spectroscopy. The transparency, thermal decomposition and static contact angle (SCA) of each sample were measured by UV-Visible spectrophotometer, TGA and drop shape analysis system, respectively. The spin coated substrates showed good superhydrophobic properties, thermal stability as well as transparency on the glass substrates.

Micro-nano structure composite cathode material with high sulfur loading for advanced lithium–sulfur batteries

ABSTRACT A micro-nano structure based on polydopamine-grafted hollow carbon nanofiber–sulfur composite (HCNF@PDA–S) is designed as a cathode material for effective trapping of sulfur and polysulfides for lithium–sulfur batteries. Hollow carbon nanofiber@polydopamine (HCNF@PDA) micro-nano structure hybrid is first prepared by an in-situ polymerization dopamine monomer decorating on the surface of HCNFs and then elemental sulfur is infiltrated into the HCNF@PDA hybrid nanostructure by thermal treatment. The obtained HCNF@PDA–S composite shows the micro-nano structure based on the micron-sized hollow carbon nanofiber in length and nano-sized polydopamine grafted on the outer surfaces of the HCNFs with homogeneously distribution of sulfur. Compared with the HCNF–S composite, HCNF@PDA–S composite with a high sulfur content of approximately 80 wt% exhibits better electrochemical performance, which delivers initial discharge capacity of 800 mAh g−1 and maintains 530 mAh g−1 after 200 cycles at 0.5 C rate. The enhancements of electrochemical performances may be attributed to the unique micro-nano hybrid structure based on HCNFs and PDA coating layer, in which the micro-sized HCNFs offer the electronic conductivity and provide a firm porous network of the cathode tolerating the volume expansion of sulfur cathode, and nano-sized PDA layers effectively prevent the dissolution of the polysulfides into the electrolyte.

High density micro-pyramids with silicon nanowire array for photovoltaic applications

We use a metal assisted chemical etch process to fabricate silicon nanowire arrays (SiNWAs) onto a dense periodic array of pyramids that are formed using an alkaline etch masked with an oxide layer. The hybrid micro-nano structure acts as an anti-reflective coating with experimental reflectivity below 1% over the visible and near-infrared spectral regions. This represents an improvement of up to 11 and 14 times compared to the pyramid array and SiNWAs on bulk, respectively. In addition to the experimental work, we optically simulate the hybrid structure using a commercial finite difference time domain package. The results of the optical simulations support our experimental work, illustrating a reduced reflectivity in the hybrid structure. The nanowire array increases the absorbed carrier density within the pyramid by providing a guided transition of the refractive index along the light path from air into the silicon. Furthermore, electrical simulations which take into account surface and Auger recombination show an efficiency increase for the hybrid structure of 56% over bulk, 11% over pyramid array and 8.5% over SiNWAs.

GaN-Based Light Emitting Diodes with Hybrid Micro-Nano Patterned Sapphire Substrate

GaN-based light emitting diodes (LEDs) have been fabricated with hybrid micro-nano patterned sapphire substrate (MNPSS). Random nano pattern distributed on the spacing and inclined surface of the micro pattern was realized utilizing standard photolithography, nickel etching mask and inductively coupled plasma (ICP) etching techniques. Both surface morphology and X-ray diffraction (XRD) results showed that MNPSS and conventional MPSS had similar effect on the crystalline quality of the epilayers. Furthermore, light output powers (LOP) of LEDs with MNPSS was increased considerably compared with conventional planar sapphire substrate (CPSS) and was even higher than that of LEDs employing micro patterned sapphire substrate (MPSS), indicating more superior performance of GaN-based LEDs was obtained by employing the hybrid micro-nano pattern. © 2013 The Electrochemical Society. [DOI: 10.1149/2.007311ssl] All rights reserved.

Double-templated electrodeposition: Simple fabrication of micro-nano hybrid structure by electrodeposition for efficient boiling heat transfer

Micro-nano hybrid structure (MNHS) that comprises of microcavities and nanowires is a specific class of MNHS that is considered to be ideal for two-phase boiling heat transfer applications. Realizing MNHS with electrodeposition is favorable in boiling heat transfer, but the realization has been very difficult and time-consuming to achieve. Here, we demonstrate a simple, robust, rapid, and photolithography-free route to fabricate MNHS that consists of individual microcavities and copper nanowires on a large area. We show that this MNHS can be extremely beneficial in boiling heat transfer compared to the state-of-the-art nanowire surface.

Micro-nano hybrid structures with manipulated wettability using a two-step silicon etching on a large area

Nanoscale surface manipulation technique to control the surface roughness and the wettability is a challenging field for performance enhancement in boiling heat transfer. In this study, micro-nano hybrid structures (MNHS) with hierarchical geometries that lead to maximizing of surface area, roughness, and wettability are developed for the boiling applications. MNHS structures consist of micropillars or microcavities along with nanowires having the length to diameter ratio of about 100:1. MNHS is fabricated by a two-step silicon etching process, which are dry etching for micropattern and electroless silicon wet etching for nanowire synthesis. The fabrication process is readily capable of producing MNHS covering a wafer-scale area. By controlling the removal of polymeric passivation layers deposited during silicon dry etching (Bosch process), we can control the geometries for the hierarchical structure with or without the thin hydrophobic barriers that affect surface wettability. MNHS without sidewalls exhibit superhydrophilic behavior with a contact angle under 10°, whereas those with sidewalls preserved by the passivation layer display more hydrophobic characteristics with a contact angle near 60°.

Synergistic effects of UV photofunctionalization and micro-nano hybrid topography on the biological properties of titanium

Titanium surfaces with micro-nano hybrid topography (nanoscale nodules in microscale pits) have been recently demonstrated to show higher biological capability than those with microtopography alone. On the other hand, UV treatment of titanium surfaces, which is called UV photofunctionalization, has recently been introduced to substantially increase the biological capability and osteoconductivity of titanium surfaces. However, synergistic effects of these two advanced surface modification technologies and regulatory factors to potentially modulate the mutual effects have never been addressed. In this study, utilization of a recently discovered controllable self-assembly of TiO 2 nanonodules has enabled the exploration of the relative contribution of different sizes of nanostructures to determine the biological capability of titanium surfaces and their relative responsiveness to UV photofunctionalization. Rat bone marrow-derived osteoblasts were cultured on titanium disks with either micropits alone, micropits with 100-nm nodules, micropits with 300-nm nodules, or micropits with 500-nm nodules, with or without UV treatment. Although UV treatment increased the attachment, spread, proliferation, and mineralization of these cells on all titanium surfaces, these effects were more accentuated (3–5 times) on nanonodular surfaces than on surfaces with micropits alone and were disproportionate depending on nanonodule sizes. For instance, on UV-treated micro-nano hybrid surfaces, cell attachment correlated with nanonodule sizes in a quadratic approximation with its peak for 300-nm nodules followed by a decline for 500-nm nodules, while cell attachment exponentially correlated with surface roughness with its plateau achieved for 300-nm nodules without a subsequent decline. Moreover, cell attachment increased in a linear correlation with the surface area, while no significant effect of the inter-irregularities space or degree of hydrophilicity was observed on cell attachment. These results suggest that the effect of UV photofunctionalization can be multiplied on micro-nano hybrid titanium surfaces compared with the surfaces with micropits alone. This multiplication is disproportionately regulated by a selected set of topographical parameters of the titanium surfaces. Among the nanonodules tested in this study, 300-nm nodules seemed to create the most effective morphological environment for responding to UV photofunctionalization. The data provide a systematic platform to effectively optimize nanostructures on titanium surfaces in order to enhance their biological capability as well as their susceptibility to UV photofunctionalization.

나노입자 마스크를 이용하여 제작한 초소수성 마이크로-나노 혼성구조

소수성 고분자를 사용하여 제작한 마이크로구조에 금 나노입자를 마스크로 이용하는 반응성이온식각(RIE: Reactive Ion Etching)을 적용하여 초소수성을 갖는 마이크로-나노 혼성구조를 제작하였다. 소수성 고분자로는 PFPE (perfluoropolyether bisurethane methacrylate)를 사용하였으며 마이크로 단일구조는 PDMS (polydimethylsiloxane) 몰드를 사용하는 스탬핑 방식으로 제작하였다. 다양한 형태로 제작한 PFPE 마이크로 단일구조와 마이크로-나노 혼성구조의 표면 접촉각을 측정하여 표면 미세구조에 따른 소수성의 변화를 관찰하였다. 마이크로 단일구조의 경우 접촉각은 안정적인 값을 보이지 못하였으나 단일 구조에 나노입자를 사용한 식각을 적용해 나노구조가 형성됨에 따라 <TEX>$150^{\circ}$</TEX> 이상의 접촉각을 갖는 초소수성 표면이 매우 높은 재현성으로 용이하게 형성되었다. Superhydrophobic micro-nano hybrid structures were fabricated by reactive ion etching of hydrophobic polymer micro patterns using gold nanoparticles as etch masks. Micro structures of perfluoropolyether bisurethane methacrylate (PFPE) were prepared by soft-lithographic technique using polydimethylsiloxane (PDMS) molds. Water contact angles on the surfaces of various PFPE micro structures and corresponding micro-nano hybrid structures were compared to examine the effects of micro patterning and nanostructure formation in the manifestation of superhydrophobicity. The PFPE micro-nano hybrid structures exhibited a very stable superhydrophobicity, while the micro-only structures could not reach the superhydrophobicity but only showed the unstable hydrophobicity.

양극산화된 알루미늄과 마이크로 인덴데이션을 이용한 3차원 마이크로-나노 하이브리드 패턴 제작

A simple method for the fabrication of 3D micro-nano hybrid patterns was presented. In conventional fabrication methods of the micro-nano hybrid patterns, micro-patterns were firstly fabricated and then nanopatterns were formatted on the micro-patterns. Moreover, these micro-nano hybrid patterns could be fabricated on the flat substrate. In this paper, we suggested the fabrication method of 3D micro-nano hybrid patterns using micro-indentation on the anodized aluminum substrate. Since diameter of the hemispherical nano-pattern can be controlled by electrolyte and applied voltage in the anodizing process, we can easily fabricated nano-patterns of diameter of 10㎚ to 300㎚. Nano-patterns were firstly formatted on the aluminum substrate, and then micro-patterns were fabricated by deforming the nano-patterned aluminum substrate. Hemispherical nano-patterns of diameter of 150㎚ were fabricated by anodizing process, and then micro-pyramid patterns of the side-length of 50㎛ were formatted on the nano-patterns using microindentation. Finally we successfully replicated 3D micro-nano hybrid patterns by hot-embossing process. 3D micro-nano hybrid patterns can be applied to nano-photonic device and nano-biochip application.

Induced Electrokinetic Transport in Micro−Nanofluidic Interconnect Devices

Hybrid micro-nanofluidic interconnect devices can be used to control analyte transfer from one microchannel to the other through a nanochannel under rest, injection, and recovery stages of operation by varying the applied potential bias. Using numerical simulations based on coupled transient Poisson-Nernst-Planck and Stokes equations, we examine the electrokinetic transport in a gateable device consisting of two 100 microm long, 1 microm wide negatively charged microchannels connected by a 1 microm long, 10 nm wide positively charged nanochannel under both positive and negative bias potentials. During injection, accumulation of ions is observed at the micro-nano interface region with the positive potential and depletion of ions is observed at the other micro-nano junction region. Net space charge in the depletion region gives rise to nonlinear electrokinetic transport during the recovery stage due to induced pressure, induced electroosmotic flow of the second kind, and complex flow circulations. Ionic currents are computed as a function of time for both positive and negative bias potentials for the three stages. Analytical expressions derived for ion current variation are in agreement with the simulated results. In the presence of multiple accumulation or depletion regions, we show that a hybrid micro-nano device can be designed to function as a logic gate.

Hybrid micro-nano structured thermal interfaces for pool boiling heat transfer enhancement

Boiling heat transfer from hybrid micro-nano structured thermal interfaces has been studied experimentally using PF5060 and deionized water as working fluids for the range of saturation temperatures Tsat between 35°C and 60°C. Various enhancement structures were fabricated using surface micromachining in silicon. The performance of the smooth and roughened silicon surfaces, bare and fully coated with carbon nanotubes (CNTs), the silicon-etched as well as CNTs-based pin-fin arrays, and the 3D microstructures have been studied in detail. The highest heat fluxes were obtained using the 3D microstructure without CNTs—these are 27 and 130W/cm2 for PF5060 and water, respectively. Experimental results indicate that use of the CNT-enabled, purely nano-structured interfaces appear to improve boiling heat transfer only at very low superheats, as compared to the smooth surfaces.