Sub-millimeter Objects Research Articles

Automatic Holonomic Mobile Micromanipulator for Submillimeter Objects Inspired by the Rhinoceros Beetle

Holonomic mobile micromanipulators driven by piezoelectric actuators offer precision and compact design. However, attaining both high speed and positioning repeatability with sufficient load capacity poses challenges, given that lightweight robots are susceptible to nonuniform driving surfaces and external forces. A holonomic beetle (HB) is proposed to realize a wide range, compact size, precise holonomic motion, automatic micromanipulation, and high‐speed movement simultaneously. Inspired by the biological makeup of a Rhinoceros Beetle, a length, weight, and load capacity of 8 cm, 74 g, and of 2000 g, respectively, are used. The HB is a two‐legged robot with a pseudoalternating tripod gait locomotion principle, with five piezoelectric actuators for XYθ displacement and switching of the contact leg. It achieves maximum walking velocities of 11.6 mm s−1 for translational motion and 19.3 deg s−1 for rotation, with a displacement resolution of 12 nm. Notably, under open‐loop control, the HB demonstrates high repeatability with a coefficient of variation of 0.3%. It exhibits the capability to climb 30°‐inclined surfaces, traverse flat surfaces with 0.1 mm bumps, and navigate 30 mm pits. Furthermore, the HB showcases practical automatic micromanipulation through visual servo control and machine learning, presenting potential applications in biomedical and microassembly fields.

Bioprinting of hair follicle germs for hair regenerative medicine.

Hair regenerative medicine is a promising approach to treat hair loss. The replication of in vivo tissue configurations and microenvironments, such as hair follicle germs, has been studied to prepare tissue grafts for hair regenerative medicine. However, such approaches should be scalable, because a single patient with alopecia requires thousands of tissue grafts. In this paper, we propose an approach for the scalable and automated preparation of highly hair-inductive tissue grafts using a bioprinter. Two collagen droplets (2µL each) containing mesenchymal and epithelial cells were placed adjacent to each other to fabricate hair-follicle-germ-like grafts. During three days of culture, the pairs of microgel beads were spontaneously contracted by cell traction forces, whereas the two cell types remained separated, where the densities of the cells and collagen were enriched more than 10 times. This approach allowed us to fabricate submillimeter objects printed with millimeter-order accuracy, facilitating scalable and automated tissue graft preparation. Because of mesenchymal-epithelial interactions, hair microgels (HMGs, i.e., collagen- and cell-enriched microgels) efficiently regenerate hair follicles and shafts when transplanted into the back skin of mice. However, the generated hair shafts mostly remain under the skin. Therefore, we printed microgel beads onto surgical suture guides arrayed on a stage. The microgel beads were contracted along with the suture guides in culture prior to transplantation. The guide-inserted HMGs significantly improved hair-shaft sprouting through the skin, owing to the control of the orientation of the HMGs transplanted into the skin. This approach is a promising strategy to advance hair regenerative medicine. STATEMENT OF SIGNIFICANCE: This study proposes an approach for the scalable and automated preparation of highly hair-inductive grafts using a bioprinter. Two collagen droplets containing mesenchymal and epithelial cells were placed adjacently. Cell traction forces caused the pairs of microgel beads to spontaneously contract in culture. Because of mesenchymal-epithelial interactions, hair microgels (HMGs) efficiently regenerated hair follicles on the back skin of mice. However, the generated hair shafts remained mostly beneath the skin. Therefore, we printed microgel beads onto surgical suture guides arrayed on a stage. The guide-inserted HMGs significantly improved hair-shaft sprouting through the skin owing to the control of the orientation of the HMGs in the skin. This approach represents a promising strategy for advancing hair regenerative medicine.

Mechanical Properties of Acoustically Levitated Granular Rafts

We investigate a model system for the rotational dynamics of inertial many-particle clustering, in which submillimeter objects are acoustically levitated in air. Driven by scattered sound, levitated grains self-assemble into a monolayer of particles, forming mesoscopic granular rafts with both an acoustic binding energy and a bending rigidity. Detuning the acoustic trap can give rise to stochastic forces and torques that impart angular momentum to levitated objects. As the angular momentum of a quasi-two-dimensional granular raft is increased, the raft deforms from a disk to an ellipse, eventually pinching off into multiple separate rafts, in a mechanism that resembles the breakup of a liquid drop. We extract the raft effective surface tension and elastic modulus and show that nonpairwise acoustic forces give rise to effective elastic moduli that scale with the raft size. We also show that the raft size controls the microstructural basis of plastic deformation, resulting in a transition from fracture to ductile failure.3 MoreReceived 17 June 2021Revised 14 February 2022Accepted 4 March 2022DOI:https://doi.org/10.1103/PhysRevX.12.021017Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAcoustic interactionsClusteringGranular materialsPolymers & Soft Matter

Optically controlled fiber-optic micro-gripper for sub-millimeter objects.

A miniature, fully optically controlled, dielectric, opto-thermally actuated tweezer/micro-gripper that is suitable for the manipulation of small objects is presented. The tweezer/micro-gripper is formed at the tip of an optical fiber and utilizes a mid-power laser diode for its actuation. The manipulation of small objects such as short pieces of optical fibers is demonstrated. Small dimensions, fully dielectric design, non-electric actuation, remote operation through the fiber, and good harsh environment compatibility (chemical, radiation, and temperature) might provide opportunities for micromanipulation in a system and areas where current solutions are inadequate.

Design and static testing of a compact distributed-compliance gripper based on flexure motion

There are precision issues with traditional rigid-body grippers due to their nature in presence of joints’ backlash and friction. This paper presents a macroscale compliant gripper to eliminate these issues for the applications in handing delicate/brittle materials such as powder granular or manipulating sub-millimetre objects such as optical fibre and micro-lens. The compliant gripper is obtained from a 2-PRRP (P: prismatic; R: revolute) kinematic mechanism, and uses distributed-compliance joints for avoiding stress-concentration and enabling large range of motion. A very compact design is achieved by using a position space principle. The compliant gripper is modelled, fabricated, followed by comprehensive testing for characterising relationships between the input displacement/force and output displacement and between the input displacement and displacement amplification ratio, and for analysing hysteresis during loading and unloading. The experimental results are compared with finite element analysis (FEA) model and linear analytical model. The testing results have suggested good performance characteristics of this compliant gripper such as a nearly linear relationship between the input and output, a nearly constant amplification ratio for closing the jaw, and negligible hysteresis error.

Heat transfer from small objects in microgravity: Experiments and analysis

Heat transfer over a sub-millimeter spheroidal solid is of interest in many engineering processes. One important mechanism of heat transfer in the above processes is natural convection which leads to heat transfer rates many times larger than that of pure conduction. Despite the huge literature devoted to natural convection heat transfer rates over spheres (and to a smaller extent over spheroids) there is not a generally accepted correlation especially for small Rayleigh numbers. Existing correlations for external geometries predict a progressively increasing contribution of natural convection to heat transfer with respect to gravity (starting from zero gravity). To test the validity of these correlations, experiments are performed for the estimation of heat transfer rates at low gravity. Heat pulses are given to a miniature thermistor with a nearly spheroidal shape immersed in a liquid and its thermal response is registered during heating in parabolic flights. The contribution of natural convection to heat transfer is undoubtedly estimated from runs in which acceleration varies from 0 to 1.8 g. Surprisingly enough, the experiments showed that the Rayleigh number must take a minimum value before non-negligible effect of natural convection on heat transfer appears (existence of a threshold Rayleigh number). In the absence of natural convection (below Ra thr) the experimental thermal response curves can be successfully described by approximating solutions of the transient heat conduction equation for the spheroidal geometry of the thermistor. Apparently, additional research is needed regarding the natural convection around sub-millimeter objects for small Rayleigh numbers.

Portable imaging system for on‐site analysis using CMOS imager—microfluidic analysis and fluorescence imaging

AbstractThis paper reports on a portable imaging system using a complementary metal oxide semiconductor (CMOS) imager for microfluidic analysis and fluorescence imaging with an organic light emitting diode (OLED). The portable CMOS imager is useful for onsite microfluidic analysis, and the OLED works as a light source for fluorescent observations. The system needs only five elements: a laptop computer, a CMOS imaging device, an optical filter, microfluidic channels, and OLEDs. Using this system, we succeeded in a bead‐based microfluidic assay, capturing the video of the trapping and releasing process. Furthermore, we observed the fluorescent beads and the dye using an OLED as the light source in this system. As a result, we found that (i) submillimeter objects could be in focus with about 1 mm distance from CMOS imaging device surface without a lens; (ii) microfluidic experiments with poly(dimethylsiloxane) channels were possible on the CMOS imager; and (iii) OLED can potentially be used as a light source for this system. We believe that this system is useful for point‐of‐care diagnostic sensing and onsite microfluidic analysis including fluorescence detection. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

An Extinction Threshold for Protostellar Cores in Ophiuchus

We have observed continuum emission at λ = 850 μm over ~4 deg2 of the Ophiuchus star-forming cloud using the Submillimeter Common-User Bolometric Array on the James Clerk Maxwell Telescope, producing a submillimeter continuum map 20 times larger than previous Ophiuchus surveys. Our sensitivity is 40 mJy beam-1, a factor of ~2 less sensitive than earlier maps. Using an automated identification algorithm, we detect 100 candidate objects. Only two new objects are detected outside the boundary of previous maps, despite the much wider area surveyed. We compare the submillimeter continuum map with a map of visual extinction across the Ophiuchus cloud derived using a combination of Two Micron All Sky Survey and R-band data. The total mass in submillimeter objects is ≈50 M☉ compared with ≈2000 M☉ in observed cloud mass estimated from the extinction. The submillimeter objects represent only 2.5% of the cloud mass. A clear association is seen between the locations of detected submillimeter objects and high visual extinction, with no objects detected at AV 15, by some mechanism (e.g., loss of nonthermal support).

The Faint Counterparts of MAMBO Millimeter Sources near the New Technology Telescope Deep Field

We discuss identifications for 18 sources from our Max-Planck-Millimeter-Bolometer (MAMBO) 1.2 mm survey of the region surrounding the NTT Deep Field. We have obtained accurate positions from Very Large Array 1.4 GHz interferometry, and in a few cases IRAM millimeter interferometry, and have also made deep BVRIzJK imaging at ESO. We find thirteen 1.2 mm sources associated with optical/near-infrared objects in the magnitude range K = 19.0-22.5, while five are blank fields at K > 22. We argue from a comparison of optical/near-infrared photometric redshifts and radio/millimeter redshift estimates that two of the 13 optical/near-infrared objects are likely foreground objects distinct from the dust sources, one of them possibly lensing the millimeter source. The median redshift of the radio-identified millimeter sources is ~2.6 from the radio/millimeter estimator, and the median optical/near-infrared photometric redshifts for the objects with counterparts is ~2.1. This suggests that those radio-identified millimeter sources without optical/near-infrared counterparts tend to lie at higher redshifts than those with optical/near-infrared counterparts. Compared to published identifications of objects from 850 μm surveys of similar depth, the median K and I magnitudes of our counterparts are roughly 2 mag fainter, and the dispersion of I-K colors is less. Real differences in the median redshifts, residual misidentifications with bright objects, cosmic variance, and small-number statistics are likely to contribute to this significant difference, which also affects redshift measurement strategies. Some of the counterparts are red in J-K (20%), but the contribution of such millimeter objects to the recently studied population of near-infrared-selected (Js-Ks > 2.3) high-redshift galaxies is only of order a few percent. The recovery rate of MAMBO sources by preselection of optically faint radio sources is relatively low (~25%), in contrast to some claims of a higher rate for Submillimeter Common-User Bolometric Array (SCUBA) sources (~70%). In addition to this difference, the MAMBO sources also appear significantly fainter (~1.5 mag in the I band) than radio-preselected SCUBA sources. We discuss the basic properties of the near-infrared/(sub)millimeter/radio spectral energy distributions of our galaxies and of interferometrically identified submillimeter sources from the literature. From a comparison with submillimeter objects with CO-confirmed spectroscopic redshifts, we argue that roughly two-thirds of the (sub)millimeter galaxies are at z 2.5. This fraction is probably larger when including sources without radio counterparts.

Optical configurations for X-ray imaging by projection

Several optical configurations aiming to create images of sub-millimetre objects with magnification from I to 100 have been experimentally tested at the ESRF BM5 beamline. A Kirkpatrick-Baez (KB) system is used for focusing the beam into a 30 microns spot and then direct projection images are recorded. Some results using a spherical crystal downstream from the KB system are presented. The possibility to focus the synchrotron. beam into a 40 microns spot using an spherical crystal in quasi-normal incidence is demonstrated and its use for projection microscopy is discussed.

High resolution digital holography

In digital Fresnel holography, present specifications of charge-coupled device cameras require the incident beams to be quasi-parallel. That implies large speckle grain size and low lateral resolution in reconstructed images. Better lateral resolutions are demonstrated in our work, down to 8 μm, allowing the observation of sub-millimetre objects by digital holography. The experimental set-up built samples the incident light distribution with a definition of 500 pixels mm −1. The maximum acceptable angle is then widened and the hologram recording and reconstruction distances are drastically reduced, as well as the speckle size. Interferometric holography was implemented for the measurement of the deformation of a sub-millimetre silicon cantilever and results in phase-contrasts imaging are also reported. The design of dedicated complementary metal-oxide-semiconductor active pixel sensor cameras is also discussed.

The Nature of the Bright Submillimeter Galaxy Population: A Radio-preselected Sample with [ITAL]I[/ITAL] ] ∼25

Deep submillimeter surveys have successfully detected distant, star-forming galaxies, which are enshrouded in vast quantities of dust and emit most of their energy at far-infrared wavelengths. These luminous galaxies are an important constituent of the universal star formation history, and any complete model of galaxy evolution must account for their existence. Although these sources have been tentatively identified with very faint and sometimes very red optical counterparts, their poorly constrained redshift distribution has made their interpretation unclear. In particular, it was not understood if these galaxies had been missed in previous surveys or if they constituted a truly new class of objects, undetectable at other wavelengths. By utilizing a radio selection technique, we have isolated a sample of 20 submillimeter objects representative of the 850 μm population brighter than 5 mJy with z 3. We show that these galaxies are so heavily dust-obscured that they remain essentially invisible to ultraviolet selection. Furthermore, relying on the radio/submillimeter flux density ratio, we estimate their redshift distribution, finding a median of two. These results are inconsistent with the existence of a very high redshift (z > 4) population of primeval galaxies (Lbol > 1012 L☉) contributing substantially to the submillimeter counts. While not a substitute for the thorough follow-up of blank-field submillimeter surveys, our results do shed light on a substantial portion of the luminous submillimeter population with z 3.