Piezoelectric deformable mirror driven by unimorph actuator arrays on multi-spatial layers.

In order to reduce the cost of the piezo actuator array deformable mirror (DM), a piezoelectric DM driven by unimorph actuator arrays on multi-spatial layers is proposed. The actuator density can be multiplied by increasing the spatial layers of the actuator arrays. A low-cost DM prototype with 19 unimorph actuators located on three spatial layers is developed. The unimorph actuator can generate a wavefront deformation up to 11 µm at an operating voltage of 50 V. The DM can reconstruct typical low-order Zernike polynomial shapes accurately. The mirror can be flattened to 0.058 µm in RMS. Furthermore, a focal spot close to Airy spot is obtained in the far field after the aberrations of the adaptive optics testing system being corrected.

Differential confocal measurement for surface topography with microstructures based on spiral scanning and wavelet filter.

This paper proposes a novel spiral-scanning laser differential confocal measurement method (SSLDCM) for fast and precise measurement of surface topography with microstructures. Spiral plane scanning is used to eliminate frequent acceleration and deceleration problems in traditional raster-scanning differential confocal measurement systems and helps to keep the measuring process efficient and stable. To solve the problem of uneven sampling distribution during spiral scanning, a variable sampling rate method is adopted to distribute the sampling points at equal intervals, which would help to reduce the time of the 3D imaging process. A denoising method based on an adaptive wavelet threshold is proposed to filter the existing noise during the measuring process. An experimental measurement platform based on SSLDCM is constructed, and the axial response curve is tested and analyzed. The linear region range of the experimental platform reaches 13 µm, and the slope is about 164.15 mV/µm. In addition, the measurement results of a silicon wafer specimen by SSLDCM show good consistency with a commercial high-precision microscope, and the largest deviation is less than 2.71%. The SSLDCM has great potential to be used in various noncontact surface measurement applications with high efficiency and accuracy.

Weak gelation of hydrophobic guar by albumin in simulated human tear solutions.

This initial study shows that hydrophobic modification of guar polymers used in eye drops forms weak gels with human serum albumin (HSA), suggesting that modified guar may offer advantages for treatment of dry eye diseases that lead to elevated HSA concentrations in tears. Specifically, hydroxypropyl guar samples were oxidized and derivatized with linear alkyl amines to give a series of modified guar polymers (MGuar) bearing hydroxypropyl, N-alkylamide, and carboxyl moieties. MGuar interactions with lysozyme and HSA were measured by binding and rheological methods as functions of the alkyl chain length and the extent of hydrophobic modification. HSA binds MGuar, giving weak gels, whereas lysozyme shows little tendency to bind MGuar or to interfere with HSA binding. Six mole percent substitution of decyl hydrophobes gave the strongest gels in the presence of HSA.

Facile phenylboronate modification of silica by a silaneboronate.

Macroscopic and colloidal silica surfaces were readily modified with alkoxysilaneboronate, IV, yielding silica surfaces with covalently bonded phenylboronic acid groups. XPS and neutron activation confirmed the presence of boron. The ability of these surfaces to specifically interact with polyols was demonstrated with polyol-coated latex and ARS, a dye that specifically couples to boronic acid groups immobilized on colloidal or macroscopic silica. This is a new, direct approach for introduction of phenylboronic acid groups onto silica surfaces.

A fine-tuning deep residual convolutional neural network for emotion recognition based on frequency-channel matrices representation of one-dimensional electroencephalography.

Emotion recognition (ER) plays a crucial role in enabling machines to perceive human emotional and psychological states, thus enhancing human-machine interaction. Recently, there has been a growing interest in ER based on electroencephalogram (EEG) signals. However, due to the noisy, nonlinear, and nonstationary properties of electroencephalography signals, developing an automatic and high-accuracy ER system is still a challenging task. In this study, a pretrained deep residual convolutional neural network model, including 17 convolutional layers and one fully connected layer with transfer learning technique in combination frequency-channel matrices (FCM) of two-dimensional data based on Welch power spectral density estimate from the one-dimensional EEG data has been proposed for improving the ER by automatically learning the underlying intrinsic features of multi-channel EEG data. The experiment result shows a mean accuracy of 93.61 ± 0.84%, a mean precision of 94.70 ± 0.60%, a mean sensitivity of 95.13 ± 1.02%, a mean specificity of 91.04 ± 1.02%, and a mean F1-score of 94.91 ± 0.68%, respectively using 5-fold cross-validation on the DEAP dataset. Meanwhile, to better explore and understand how the proposed model works, we noted that the ranking of clustering effect of FCM for the same category by employing the t-distributed stochastic neighbor embedding strategy is: softmax layer activation is the best, the middle convolutional layer activation is the second, and the early max pooling layer activation is the worst. These findings confirm the promising potential of combining deep learning approaches with transfer learning techniques and FCM for effective ER tasks.

Silkworm-inspired electrohydrodynamic jet 3D printing of composite scaffold with ordered cell scale fibers for bone tissue engineering.

The combination of biomimetic and 3D printing has created novel opportunities for the manufacture of 3D engineered materials. A sub-microscale E-Jet 3D printing method, inspired by the dehydration and protein enrichment process of silkworm, was developed to fabricate composite bone tissue scaffold with the characteristics of controllability, fast and inexpensive. By applying the resultant effects of thermal field and flow field to low viscous composite ink, the concentration gradient biopolymer ink was obtained near the needle tip, mimicking the advanced dehydration of natural spinning apparatus. After electrical shearing force were applied on concentration gradient ink, a stable and fine jet formed. Various printing modes (droplet, continuous fiber) and structure resolutions were achieved by adjusting local solvent evaporation. Thin film, high resolution 2D structures, high aspect ratio well-bonding 3D structures were fabricated. The printed result showed that a 100 µm-sized needle could be employed directly to print patterning down to 800 nm. The printed composite scaffold with controllability of fiber size and space has been proved the feasibility as a medium for bone tissue regeneration. It can be estimated that the novel biomimetic E-Jet 3D printing technique is a new and promising way for bone tissue repairing.

Tip-Viscid Electrohydrodynamic Jet 3D Printing of Composite Osteochondral Scaffold.

A novel method called tip-viscid electrohydrodynamic jet printing (TVEJ), which produces a viscous needle tip jet, was presented to fabricate a 3D composite osteochondral scaffold with controllability of fiber size and space to promote cartilage regeneration. The tip-viscid process, by harnessing the combined effects of thermal, flow, and electric fields, was first systematically investigated by simulation analysis. The influences of process parameters on printing modes and resolutions were investigated to quantitatively guide the fabrication of various structures. 3D architectures with high aspect ratio and good interlaminar bonding were printed, thanks to the stable fine jet and its predictable viscosity. 3D composite osteochondral scaffolds with controllability of architectural features were fabricated, facilitating ingrowth of cells, and eventually inducing homogeneous cell proliferation. The scaffold's properties, which included chemical composition, wettability, and durability, were also investigated. Feasibility of the 3D scaffold for cartilage tissue regeneration was also proven by in vitro cellular activities.

Cationic liposome colloidal stability in the presence of guar derivatives suggests depletion interactions may be operative in artificial tears.

The colloidal stability of cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) liposomes was measured in the presence of guar, carboxymethyl guar, hydroxypropyl guar (HPG), and in mixtures of HPG with boric acid. Carboxymethyl guar induced DOTAP aggregation, presumably by bridging flocculation. The interaction with HPG-borate, an anionic polyelectrolyte with labile charge groups, depended on ionic strength. Without added salt, HPG-borate (pH 9.2) adsorbed on the liposomes and destabilized them. In contrast, in 0.1 M NaCl, HPG-borate did not adsorb onto the liposomes. HPG, HPG-borate, and guar induced depletion flocculation of the liposomes at high polymer concentration. Depletion flocculation may be an important mechanism when HPG is employed in artificial tear formulations.

Not all anionic polyelectrolytes complex with DTAB.

The influence of hydroxypropyl guar (HPG), with and without boric acid, on dodecyltrimethyl ammonium bromide (DTAB) micellization was characterized by surface tension measurements, isothermal titration calorimetry, and small-angle neutron scattering. Although HPG is a nonionic water-soluble polymer, borate ions form weak bonds with HPG, transforming it into an anionic polyelectrolyte, HPG-borate. Surprisingly, the three independent measurements showed that HPG-borate does not promote DTAB micellization or phase separation normally seen when mixing oppositely charged polyelectrolytes and surfactants. However, the neutron scattering results suggested that HPG-borate binds to and flocculates existing DTAB micelles. The unusual behavior of HPG-borate with DTAB was underscored by showing that carboxymethyl guar (CMG) formed precipitates with DTAB.

DNA aptamer folding on gold nanoparticles: from colloid chemistry to biosensors.

We have investigated the effect of the folding of DNA aptamers on the colloidal stability of gold nanoparticles (AuNPs) to which an aptamer is tethered. On the basis of the studies of two different aptamers (adenosine aptamer and K+ aptamer), we discovered a unique colloidal stabilization effect associated with aptamer folding: AuNPs to which folded aptamer structures are attached are more stable toward salt-induced aggregation than those tethered to unfolded aptamers. This colloidal stabilization effect is more significant when a DNA spacer was incorporated between AuNP and the aptamer or when lower aptamer surface graft densities were used. The conformation that aptamers adopt on the surface appears to be a key factor that determines the relative stability of different AuNPs. Dynamic light scattering experiments revealed that the sizes of AuNPs modified with folded aptamers were larger than those of AuNPs modified with unfolded (but largely collapsed) aptamers in salt solution. From both the electrostatic and steric stabilization points of view, the folded aptamers that are more extended from the surface have a higher stabilization effect on AuNP than the unfolded aptamers. On the basis of this unique phenomenon, colorimetric biosensors have been developed for the detection of adenosine, K+, adenosine deaminase, and its inhibitors. Moreover, distinct AuNP aggregation and redispersion stages can be readily operated by controlling aptamer folding and unfolding states with the addition of adenosine and adenosine deaminase.

Nanoparticle flotation collectors III: the role of nanoparticle diameter.

The ability of polystyrene nanoparticles to promote glass bead flotation was measured as a function of nanoparticle diameter. In all cases, smaller nanoparticles were more effective flotation collectors, even when compared at constant nanoparticle number concentration. The superior performance of smaller particles was explained by two mechanisms, acting in parallel. First, smaller particles deposit more quickly giving more effective flotation in those cases where nanoparticle deposition kinetics is rate determining; the sensitivity of nanoparticle deposition rates to particle size was illustrated by kinetic measurements on a quartz crystal microbalance silica surface. Second, for a given coverage of nanoparticles on the glass beads, the mean distance between neighboring nanoparticle surfaces decreases with particle diameter. We propose that the expansion of the three phase contact line, after initial bead/bubble attachment, is favored with decreasing the distance between neighboring hydrophobic particles.

Shapes of polyelectrolyte titration curves. 1. Well-behaved strong polyelectrolytes.

The charge content of aqueous polymers is measured routinely by polyelectrolyte titrations in which an unknown polymer is titrated with an oppositely charged standard polymer solution, usually poly(diallyldimethyl ammonium chloride) or potassium poly(vinyl sulfate). Polyelectrolyte titration end points are frequently determined with a streaming current detector (SCD). The shapes of polyelectrolyte titration curves from polyelectrolytes with fixed electrical charges were simulated by a diffuse electrical double layer model. Well-behaved titration curves obtained with fixed charged polyelectrolytes were fit by the modeling, giving support for the basic hypothesis that the net charge of material adsorbed on the SCD wall is a linear function of the volume of added titrant. The shapes of titration curves from deviant systems such as poly(vinyl alcohol)-borate cannot be predicted by the model.