The thermal position fluctuations of a single micron-sized sphere immersed in fluid were recorded by optical trapping interferometry with nanometer spatial and microsecond temporal resolution. We find, accord the theory Brownian motion including hydrodynamic memory effects, that transition from ballistic to diffusive is delayed significantly longer times than predicted standard Langevin equation. This delay consequence inertia fluid. On shortest time scales investigated, sphere's has small,...

The equilibrium dynamics of a spherical particle immersed in complex Maxwell fluid is analyzed terms velocity autocorrelation function (VACF), mean-square displacement (MSD), and power spectral density (PSD). We elucidate the role hydrodynamic memory its interplay with medium viscoelasticity for free harmonically confined particle. elastic response at high frequencies introduces oscillations VACF, which are found to be strongly damped by coupling fluid. show that all fluids eventually leads...

We have developed an in situ method to calibrate optical tweezers experiments and simultaneously measure the size of trapped particle or viscosity surrounding fluid. The positional fluctuations are recorded with a high-bandwidth photodetector. compute mean-square displacement, as well velocity autocorrelation function sphere, compare it theory Brownian motion including hydrodynamic memory effects. A careful measurement analysis time scales characterizing dynamics harmonically bound sphere...

Thermal position fluctuations of a colloidal particle in an optical trap are measured with microsecond resolution using back-focal-plane interferometry. The mean-square displacement <Delta(x)2(t)> and power spectral density excellent agreement the theory for Brownian harmonic potential that accounts hydrodynamic memory effects. motion is dominated at short times by effects longer potential. We identify time below which particle's not influenced potential, find it to be approximately...

The motion of an optically trapped sphere constrained by the vicinity a wall is investigated at times where hydrodynamic memory significant. First, we quantify, in bulk, influence confinement arising from trapping potential on sphere's velocity autocorrelation function $C(t)$. Next, study splitting $C(t)$ into ${C}_{\ensuremath{\parallel}}(t)$ and ${C}_{\ensuremath{\perp}}(t)$, when approached towards surface. Thereby, monitor crossover slow ${t}^{\ensuremath{-}3/2}$ long-time tail, away...

We investigate the diffusive motion of micron-sized spherical tracers in a viscoelastic actin filament network over time span 8 orders magnitude using optical-tweezers single-particle tracking. The hydrodynamic interactions tracer with surrounding fluid are shown to dominate at microsecond scales, while subdiffusive scaling due properties medium emerges millisecond scales. transition between these two regimes is analyzed frame minimal phenomenological model which combines Basset force and...

A new method combining three-dimensional (3D) force measurements in an optical trap with the analysis of thermally induced (Brownian) position fluctuations a trapped probe was used to investigate mechanical properties single molecule, molecular motor kinesin. One kinesin molecule attached bound rigorlike state one microtubule. The kept weak measure thermal forces acting on probe, which were mainly counterbalanced by tether. stiffness during stretching and compression respect its backbone...

Experimental studies of carbon nanotubes (CNTs) obtained through different synthesis routes show considerable variability in their mechanical properties. The strongest CNTs so far had a high Young's modulus 1 TPa but could only be produced gram scale quantities. by catalytic chemical vapor deposition, method that holds the greatest potential for large-scale production, gives with defect density. This leads to low values below 100 GPa multiwall CNTs. Here we performed direct measurements...

Nanocrystalline titanium dioxide (nanoTiO2) has been reported to generate reactive oxygen species (ROS) under UV illumination. In our studies, changes in mechanical properties of human skin fibroblasts, exposed the oxidative stress induced presence nanoTiO2 and light, were studied using atomic force microscopy (AFM). The exposure cells action ROS was performed at low TiO2 concentration (4 μg/mL) illumination with low-intensity UVA (8 20 mW/cm2) or UVC (0.1 mW/cm2). AFM measurements cell...

We have investigated the motion of a single optically trapped colloidal particle close to limiting wall at time scales where inertia surrounding fluid plays significant role. The velocity autocorrelation function exhibits complex interplay due momentum relaxation particle, vortex diffusion in fluid, obstruction flow interface, and harmonic restoring forces optical trap. show that already weak trapping force has impact on C(t)=<v(t)v(0)> times hydrodynamic memory leads an algebraic decay....

We study the Brownian motion of microbeads immersed in water and a viscoelastic wormlike micelles solution by optical trapping interferometry diffusing wave spectroscopy. Through mean-square displacement obtained from both techniques, we deduce mechanical properties fluids at high frequencies explicitly accounting for inertia effects particle surrounding fluid short time scales. For micelle solutions, recover 3/4 scaling exponent loss modulus over two decades frequency as predicted theory...

Near-infrared (NIR) light sensitive lanthanide-doped NaYF4 upconversion particles (UCPs) are gaining increasing attention as local probes in biomedical applications. Here, we implemented a photonic force microscope (PFM) to manipulate and study the optical properties of trapped single UCPs, β-NaYF4:Yb,Er. In particular, focused on mechanisms trapping nonspherical UCPs different sizes, range 0.5–2 μm, well their photoluminescence (UCL) under excitation with strongly laser beam (λ = 1064 nm)...

Uniformly dispersed deposition of various nanoparticles (gold and silver 20–50nm) nanowires (ZnO VOx) on different surfaces (Si, GaAs, mica, steel) was obtained by boiling colloid drops preheated substrates. Our results suggest a mechanism based the formation microdrops induced boiling. Indeed, produced an ink-jet printing system resulted in uniformly deposits when substrate heated to high temperatures. We demonstrate that boil-deposited gold could be used for catalytic growth ZnO as well...

Huntington's disease (HD), caused by a mutation of the corresponding gene encoding protein huntingtin (htt), is characterized progressive deterioration cognitive and motor functions, paralleled extensive loss striatal neurons. At cellular level, pathogenesis involves an early prolonged period neuronal dysfunction followed death. Understanding molecular events driving these deleterious processes critical to successful development therapies slow down or halt progression disease. Here, we...

We demonstrate quantitative in situ viscosity measurements by tracking the thermal fluctuations of an optically trapped microsphere subjected to a small oscillatory flow. The measured power spectral density sphere’s positions displays characteristic peak at driving frequency flow, which is simply proportional viscosity, when units same frequency. Measurements are validated on different water-glycerol mixtures, as well glycerol gradient, where no priori knowledge solution used determine concentration.

We introduce a method for the acquisition of single molecule force measurements ligand-receptor interactions using photonic microscope (PFM). Biotin-functionalized beads, manipulated with an optical trap, and streptavidin-functionalized coverslip were used to measure effect different pulling forces on lifetime individual streptavidin-biotin complexes. By optimizing design trap selection appropriate bead size, in excess 50 pN achieved. Based amplitude three-dimensional (3D) thermal position...

To understand cell—cell interactions and the of cells to non‐biological materials, studies on binding forces between cellular proteins material such as metal surfaces are essential. The adsorption solid—water interfaces is a multifactorial multistep process. First steps determined by long‐range where surface properties hydrophobicity, distribution charged groups, ion concentrations pH play important roles. In later structural rearrangements in protein molecule dehydration effects become more...