Micromanipulation

An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in which the

Three types of highly-customizable open source probe positioning systems are evaluated: (a) mostly 3-D printed, (b) partially printed using OpenBeam kinematic constraints, and (c) a 3-level stack of low-cost commercial single axis micropositioners and some printed parts. All systems use digital distributed manufacturing to enable bespoke features, which can be fabricated with RepRap-class 3-D printer and easily accessible components. They are all flexible in material choice for custom components. The micropositioners can be set up for left-right use and flat or recessed configurations using either mechanical or magnetic mounting. All systems use a manual probe holder that can be customized and enable a quick swap probe system. System (a) is purchased for $100 or fabricated for <$5, (b) fabricated for $25, and (c) fabricated for $145. Each full turn of a knob moves an axis 0.8 mm for (a) and 0.5 mm for (b,c) providing externally measured positional control of 10 microns for the latter. All three designs can utilize a customizable probe holder and tungsten carbide needle for $56. The designs are validated using microchips with known feature sizes and underwent mechanical stress tests. The maximal deflection of (a) was >200 microns, (b) 40 microns and (c) 10 microns. A tradeoff is observed for 3-D printed percent between cost and accuracy. All systems provided substantial cost savings over proprietary products with similar functionality.

Using the recently developed single molecule force-clamp technique we quantitatively measure the kinetics of conformational changes of polyprotein molecules at a constant force. In response to an applied force of 110 pN, we measure the dwell times of 1647 unfolding events of individual ubiquitin modules within each protein chain. We then establish a rigorous method for analyzing force-clamp data using order statistics. This allows us to test the success of an history independent, two-state model in describing the kinetics of the unfolding process. We find that the average unfolding trajectory is independent of the number of protein modules N in each trajectory, which varies between 3 and 12 (the engineered protein length), suggesting that the unfolding events in each chain are uncorrelated. We then derive a binomial distribution of dwell times to describe the stochastic dynamics of protein unfolding. This distribution successfully describes 81 % of the data with a single rate consta...

Ultrafast time-gated fluorescence imaging of optically trapped single motile cells is presented. The biflagellar green microalga Haematococcus pluvialis was confined with picoNewton trapping forces in the focal volume of a high numerical aperture objective by near infrared multitraps. Trapping radiation of 100 mW power at the sample was provided by a Nd:YLF laser (1047 nm) operating in the cw mode. Simultaneously, cellular autofluorescence was excited with a 633 nm picosecond 80 MHz laser diode. An ultrafast gated intensified slow scan CCD camera system with a tunable gate width (200 ps-1 ms) and tunable time-delay (0-20 ns) between excitation and detection was used as fluorescence detector. We demonstrate fluorescence imaging of high temporal (sub-ns) and high spatial (sub-microm) resolution and fluorescence lifetime determination of intracellular autofluorescence based on chlorophyll excitation. Exposure to the herbicide DCMU resulted in an increase of fluorescence intensity and l...

BackgroundIntracytoplasmic sperm injection (ICSI) requires long training and has low success rates, primarily due to poor control over the injection force. Making force feedback available to the operator will improve the success rate of the injection task. A macro–micro-teleoperation system bridges the gap between the task performed at the micro-level and the macroscopic movements of the operator. The teleoperation slave manipulator should accurately position a needle to precisely penetrate a cell membrane. Piezoelectric actuators are widely used in micromanipulation applications; however, hysteresis non-linearity limits the accuracy of these actuators.Intracytoplasmic sperm injection (ICSI) requires long training and has low success rates, primarily due to poor control over the injection force. Making force feedback available to the operator will improve the success rate of the injection task. A macro–micro-teleoperation system bridges the gap between the task performed at the micro-level and the macroscopic movements of the operator. The teleoperation slave manipulator should accurately position a needle to precisely penetrate a cell membrane. Piezoelectric actuators are widely used in micromanipulation applications; however, hysteresis non-linearity limits the accuracy of these actuators.MethodThis paper presents a novel approach for utilizing a piezoelectric nano-stage as slave manipulator of a teleoperation system. The Prandtl–Ishlinskii (PI) model is used to model actuator hysteresis in a feedforward scheme to cancel out this non-linearity. To deal with the influence of parametric uncertainties, unmodelled dynamics and PI identification error, a perturbation term is added to the slave model and applies a sliding mode-based impedance control with perturbation estimation.This paper presents a novel approach for utilizing a piezoelectric nano-stage as slave manipulator of a teleoperation system. The Prandtl–Ishlinskii (PI) model is used to model actuator hysteresis in a feedforward scheme to cancel out this non-linearity. To deal with the influence of parametric uncertainties, unmodelled dynamics and PI identification error, a perturbation term is added to the slave model and applies a sliding mode-based impedance control with perturbation estimation.ResultsThe stability of entire system is guaranteed by Llewellyn's absolute stability criterion. The performance of the proposed controller was investigated through experiments for cell membrane penetration.The stability of entire system is guaranteed by Llewellyn's absolute stability criterion. The performance of the proposed controller was investigated through experiments for cell membrane penetration.ConclusionThe experimental results verified the accurate position tracking in free motion and simultaneous position and force tracking in contact with a low stiffness environment. Copyright © 2009 John Wiley & Sons, Ltd.The experimental results verified the accurate position tracking in free motion and simultaneous position and force tracking in contact with a low stiffness environment. Copyright © 2009 John Wiley & Sons, Ltd.

We propose a technique that permits one to increase by one order of magnitude the detection range of position sensing for the photonic force microscope with quadrant photodetectors (QPDs). This technique takes advantage of the unavoidable cross-talk between output signals of the QPD and does not assume that the output signals are linear in the probe displacement. We demonstrate the increase in the detection range from 150 to 1400 nm for a trapped polystyrene sphere with radius of 300 nm as probe.