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The concentrated photovoltaic (CPV) can be employed to improve the efficiency of solar cells and reduce the systemcost of power generation, which is the primary part of the CPV system. Based on the demands for the concentrators to have an ultrathin and ultralight design, a design of ultrasmall aspect ratio concentrators is proposed. The concentrator is formed by a lens array and a freeform reflector to precisely control the light. The solar cell is placed at the side of the concentrator, which greatly reduces the overall thickness of the concentrator. The design can reduce the aspect ratio of concentrator by a considerable amount. The freeform reflector can shape the light beam and achieve a uniform distribution of light energy. [ABSTRACT FROM AUTHOR]

A micro/nano force can be traced to the International System of Units by means of an electrostatic force balance weight system. However, the micro/nano force measurement system is susceptible to environmental disturbances. Various methods have been proposed to reduce the effect of environmental disturbances and obtain high resolution and fast response. In this paper, we introduce a combination of air damping and inherent damping from the internal molecular friction of spring suspension. This will optimize system stability and improve environmental noise suppression. Results from the air damping model show that the damping ratio increases from 0.0005 to 0.1, which improves the vibration resistance. We found that the system with air damping has the advantages of fast response and low scatter. [ABSTRACT FROM AUTHOR]

It is now ascertained that traditional electric sensors are vulnerable to electromagnetic interference when measuring viscosity. Here, we propose a new viscosity-sensitive structure based on the fiber Bragg grating (FBG) sensing principle and a micro-vibration measurement method. The symmetric micro-vibration motivation method is also described, and a mathematical model for compensational voltage and fluid viscosity is established. The probe amplitude, which is produced by reciprocating stimulation, is accessible by means of an FBG sensor mounted on an equal-strength beam. Viscosity can be therefore calculated using a demodulation technique based on linear edge filtering with long period grating. After performing a group of verifying tests, the sensor has been subsequently calibrated with a series of standard fluids to determine uncertain parameters in the mathematical model. The results of the experiment show that the relative measurement error was less than 2% when the viscosity ranged from 200 to 500 mPa s. The proposed architecture utilizes the characteristics of anti-interference, fast response speed, high resolution and compact structure of FBG, thereby offering a novel modality to achieve an online viscosity measurement. [ABSTRACT FROM AUTHOR]

Three types of indirect phase tuning-based plasmonic structures with subwavelength circular grooves/slits and/or central apertures corrugated on Au film supported by glass substrate: depth modulation, width modulation, and hybrid depth-width modulation, were put forth in this paper. They were investigated experimentally by means of nanofabrication and near-filed scanning optical microscope characterization. The plasmonic structures were fabricated using the technique of focused ion beam direct milling. Our experimental results demonstrated that all of the phase tuning-based structures have focusing functions. Both the width and depth modulation-based structures can realize beam focusing and produce an elongated depth of focus. Moreover, after comparison among these three structures, we found that the width modulation-based structure has the best focusing performance. [ABSTRACT FROM AUTHOR]

Light carries energy and momentum, which can be transferred to the irradiated target during the process of reflection, refraction or transmission. The energy transfer can be seen from heat generation and thermal expansion of the target, while the momentum can exert a microscopic force, called an optical force, that is extremely difficult to detect because it is so small. A theoretical model for describing the force distribution on a macroscopic spherical mirror irradiated by a single laser pulse is established in this study. Finite element analysis has been performed to predict the dynamics of the mirror and it shows good consistency with the experimental results. It indicates the differences in the variation of mechanical response due to the optical force and thermal deformation due to photon absorption. A parametric study was also performed to analyze the relationship between mirror geometry and laser dynamics. These studies verify the thermal-mechanical coupling in light-material interactions for a pulsed-laser irradiation model, thereby being applicable in precision measurement of optical force at a microscopic level. [ABSTRACT FROM AUTHOR]

The replication accuracy of micro features plays a very important role in polymeric micro devices, such as microfluidic and micro optics. However, there is no effective way at the moment for the assessment of manufacturability of such microstructures. This study develops a new method of using a star pattern with a continuous change of width and aspect ratio to characterize the manufacturability of microstructures. The designed patterns have a width from 20 microns to 320 microns with an aspect ratio from 2.5 to 0.156. Concentric markers are designed on the star patterns for the easy identification of achievable feature accuracy under various processes. It is found that the dry etching and electroforming cause a depth error of less than 5%, while the maximum error from injection moulding is 2.8% where the channel aspect ratio is less than 1. However, when the aspect ratio of protrusion microstructures is higher than 1 with a width of 50 µm, insufficient filling occurs under nominal injection moulding conditions with relative error more than 10%. The designed star patterns are proved to be an easy and fast way to determine achievable feature accuracy for polymer micro replication processes, including injection moulding and hot embossing. [ABSTRACT FROM AUTHOR]

Stylus profilometry is one of the most significant technologies to measure freeform surfaces. However, the lateral force on a stylus usually leads to invalid measurements, especially for surfaces with a large curvature, due to the structure of the cantilever. Thus, we propose a novel radial scanform measurement for such surfaces, with an aim to reduce measurement errors. The precise 3D form of the workpiece was obtained using a series of profiles measured individually along the radial direction via a rotary mechanism. The lateral slope and force on the stylus for every profile are therefore much lower than those measured by traditional raster scan form measurements. We also propose a stable and accurate two-step registration procedure to evaluate the freeform surface form error; this eliminates the need to calibrate the spindle of both the workpiece and the rotary mechanism. A freeform surface with a 30 mm diameter aperture and 24 mm curvature radius was measured on a Form Taylorsurf PGI 1250A profilometer. Compared to traditional raster scan 3D form measurements, the peak-to-valley and root mean squared values of the form error decrease from 409.415 µm and 67.490 µm to 4.967 µm and 0.658 µm, respectively, via the proposed method. Results show that our method solves the problems of measuring surfaces with a large curvature. [ABSTRACT FROM AUTHOR]

A new approach to precision electroforming of a wafer scale nickel shim using a rotating cathode with an auxiliary cathode mask is developed to improve thickness uniformity and flatness. The effects of critical process parameters, including cathode rotating speed, cathode mask size, and current density, on the thickness uniformity and flatness of electroformed nickel shim are systematically studied based on experiments and simulations. The results show that the thickness uniformity of the deposits is highly dependent on the current density distribution, where a cathode mask can effectively tune electrical field lines and induce a more uniform current density distribution. The simulations and experimental results consistently agree that a minimum thickness nonuniformity of 8% and below 1% on the wafer with a diameter of 80 mm and 40 mm, respectively, can be achieved using a mask with a 70 mm opening size. However, for flatness, the cathode rotating speed influences the surface warpage due to the intrinsic stress. It is also found that the gradient current density can significantly reduce the intrinsic stress with better flatness. The best flatness is controlled below 47 µm and 32 µm on the wafer with diameters of 80 mm and 40 mm, respectively, under the synergistic effect of optimal cathode rotating speed (30 rpm) and gradient current density. [ABSTRACT FROM AUTHOR]

Micro injection moulding has been demonstrated as one of the most efficient mass production technologies for manufacturing polymeric microfluidic devices, which have been widely used in life sciences, environmental and analytical fields and agro-food industries. However, the filling of micro features for typical microfluidic devices is complicated and not yet fully understood, which consequently restricts the chip development. In the present work, a microfluidic flow cytometer chip with essential high aspect ratio micro features was used as a typical model to study their filling process. Short-shot experiments and single factor experiments were performed to examine the filling progress of such features during the injection and packing stages of the micro injection moulding process. The influence of process parameters such as shot size, packing pressure, packing time and mould temperature were systematically monitored, characterised and correlated with 3D measurements and real response of the machine such as screw velocity and screw position. A combined melt flow and creep deformation model was proposed to explain the complex influence of process on replication. An approach of over-shot micro injection moulding was proposed and was shown to be effective at improving the replication quality of high aspect ratio micro features. [ABSTRACT FROM AUTHOR]

An effective wavefront aberration analysis method for measuring spectacle lenses in as-worn status was proposed and verified using an experimental apparatus based on an eye rotation model. Two strategies were employed to improve the accuracy of measurement of the effective wavefront aberrations on the corneal sphere. The influences of three as-worn parameters, the vertex distance, pantoscopic angle, and face form angle, together with the eye rotation and corresponding incident beams, were objectively and quantitatively obtained. The experimental measurements of spherical single vision and freeform progressive addition lenses demonstrate the accuracy and validity of the proposed method and experimental apparatus, which provide a potential means of achieving supernormal vision correction with customization and personalization in optimizing the as-worn status-based design of spectacle lenses and evaluating their manufacturing and imaging qualities. [ABSTRACT FROM AUTHOR]

Reflective axicons, widely used in optical alignment and Bessel–Gauss beam generation, require a highly accurate cone angle and surface metrology. However, current methods focus on the cone angle measurement and it is still difficult to measure the surface of a reflective axicon with a small cone angle. An interferometer measurement method using an optical inner surface is proposed to obtain the surface and cone angle simultaneously. The optical axis of the axicon and the optical inner surface should align together and be parallel to the beam light from the interferometer. The interference fringe would be obtained by the optical system consisting of the axicon and the optical inner surface. The theoretical model is established and analyzed through ray tracing theory, and is verified by optical simulation software. Fabrication errors in the axicon and the inner surface, and misalignment of the measurement setup are investigated systematically and separated in the measurement process. In the experiments, the reflective axicon with a cone angle of about 90° was measured by the proposed method, the results of which show good agreement with a stylus profiler (Taylor-Hobson PGI 3D) in cone angle trend and generatrix error. Experimental results prove the feasibility of the proposed method. This economical and effective method can be widely used with all types of reflective axicons, and it can obtain the surface error map of the axicon as well as the inner cylinder at the same time. The uncertainty and resolution of the proposed method is based on the performance of the interferometer. The uncertainty of alignment angle errors is less than 10−10 rad; the lateral resolution is 53.8 µm. [ABSTRACT FROM AUTHOR]

Calibration of the stiffness of atomic force microscope (AFM) cantilevers is critical for industry and academic research. The multi-position calibration method for AFM cantilevers based on vibration is investigated. The position providing minimum uncertainty is deduced. The validity of the multi-position approach is shown via theoretical and experimental means. We applied it to the recently developed vibration method using an AFM cantilever with a normal stiffness of 0.1 N m−1. The standard deviation of the measured stiffness is 0.002 N m−1 with a mean value of 0.189 N m−1 and the relative combined uncertainty is approximately 7%, which is better than the approach using the single position at the tip of the cantilever. [ABSTRACT FROM AUTHOR]

Nanomanufacturing is an emerging technology in the field of synthesis of nanomaterials, manufacture of nanodevices, nanosystems and the relevant characterization technologies, and will greatly impact our society and environment: speeding up scientific discovery, technological development, improving healthcare and living standards and slowing down the exhaustion of energy resources, to name but few. The 1st International Conference on Nanomanufacturing (NanoMan2008) was held on the 13-16 July 2008 in Singapore in conjunction with ThinFilm2008 (The 4th International Conference on Technological Advances of Thin Films & Surface Coatings). Approximately 140 delegates from all over the world have participated in the conference and presented their latest discoveries and technological developments. The main focuses of the conference were modern nanomanufacturing by laser machining, focused ion beam fabrication, nano/micro-molding/imprinting, nanomaterial synthesis and characterization, nanometrology and nano/microsystems fabrication and characterization. There was also great interest in applications of nanomanufacturing technologies in traditional areas such as free form machining, polishing and grinding with nano-scale precision and the smoothness of surfaces of objects, and applications in space exploration, military and medicine. This special issue is devoted to NanoMan2008 with a collection of 9 invited talks presented at the conference, covering all the topics of nanomanufacturing technology and development. These papers have been upgraded by the authors with new results and discoveries since the preparation of the conference manuscripts, hence presenting the latest developments. We would like to take this opportunity to thank all the delegates who attended the conference and made the conference successful, and to the authors who contributed papers to this special issue. Thanks also go to the conference committee for their efforts and devotion to the conference. We would like to express our sincere thanks to Dr Ian Forbes and the other members of editorial board of the Journal of Micromechanics and Microengineering of the Institute of Physics for their help and support in making this special section. The conference was a success. We found there is a great demand for continuation of the conference, and it has been agreed by the conference committee to hold the conference biannually from now on. The 2nd International Conference on Nanomanufacturing (NanoMan2010) is to be held in Tianjin, China in 2010. On behalf of the committee we would like to take this opportunity to welcome everybody to NanoMan2010. [ABSTRACT FROM AUTHOR]

Recently, the possibility of achieving one-way backscatter immune transportation of light by mimicking the topological properties of certain solid state systems, such as topological insulators, has received much attention. Thus far, however, demonstrations of nontrivial topology in photonics have relied on photonic crystals with precisely engineered lattice structures, periodic on the scale of the operational wavelength and composed of finely tuned, complex materials. Here we propose a novel effective medium approach towards achieving topologically protected photonic surface states robust against disorder on all length scales and for a wide range of material parameters. Remarkably, the nontrivial topology of our metamaterial design results from the Berry curvature arising from the transversality of electromagnetic waves in a homogeneous medium. Our investigation therefore acts to bridge the gap between the advancing field of topological band theory and classical optical phenomena such as the spin Hall effect of light. The effective medium route to topological phases will pave the way for highly compact one-way transportation of electromagnetic waves in integrated photonic circuits. [ABSTRACT FROM AUTHOR]