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We demonstrate controllable poration within ≈1 µm regions of individual cells, mediated by a near-IR laser interacting with thin-layer amorphous silicon substrates. This technique will allow new experiments in single-cell biology, particularly in neuroscience. As our understanding of the fundamental mechanistic processes underpinning biology expands, so does the need for high-precision tools to allow the dissection of the heterogeneity and stochastic processes that dominate at the single- and sub-cellular level. Here, we demonstrate a highly controllable and reproducible optical technique for inducing poration within specific regions of a target cell’s plasma membrane, permitting localized delivery of payloads, depolarization and lysis experiments to be conducted in unprecedented detail. Experiments support a novel mechanism for the process, based upon a thermally-induced change triggered by the interactions of a near-IR laser with a biocompatible thin film substrate at powers substantially below that used in standard optoporation experiments.

Electropolymerized poly( o -toluidine) (P o T) films in the fully reduced state were studied using in situ neutron reflectivity. Acquisition of specular reflectivity profiles (as a function of neutron momentum transfer) for films exposed to perchloric acid solutions using H 2 O and D 2 O as solvents (‘contrast variation’) allowed extraction of structural information. In particular, it was possible to determine the polymer and solvent volume fractions within the film as functions of distance perpendicular to the interface. The data fit a single homogeneous layer model with a diffuse outer polymer ∣ solution interface. Within the interior of the film, the solvent volume fraction was small and varied with electrolyte composition. Film thickness increased monotonically with perchloric acid concentration: this was attributed to increased solvent content at low concentration and perchloric acid permeation at high concentration.

We have developed holographic optical tweezers that can manipulate many particles simultaneously in three dimensions in order to create micro-crystal structures that extend over many tens of microns. The technique uses specific hologram-design algorithms to create structures that can be dynamically scaled or rotated about arbitrary axes. We believe the generation and control of pre-determined crystal-like structures have significant potential in fields as diverse as photonic-crystal construction, seeding of biological tissue growth and creation of metrological standards within nanotechnology.

Here we describe the synthesis and electrochemical polymerisation of 2,5-di(2-thienyl)-3-(3-cyanopropyl)pyrrole, 2,5-di(2-thienyl)-3-(3-cyanopropyl)furan, and 3′-(3-cyanopropyl)-2,2′:5′,2″-terthiophene. We report a synthetic methodology to these important conducting polymer precursor compounds that is facile, convenient and flexible. The key precursor to this study is the functionalised diketone 1,4-bis(2-thienyl)-2-(3-cyanopropyl)butane-1,4-dione. This molecule undergoes convenient ring closure to the terthiophene and dithienylpyrrole and dithienylfuran derivatives, all of which are, to our knowledge, new compounds. Importantly, this approach provides a flexible route to a range of heterocyclic polymer precursors because the cyanoalkyl functionality is grafted to the diketone before ring closure. Subsequently the nitrile group provides synthetic utility either by reduction to the amine, or hydrolysis to the carboxylic acid. The new compounds described here undergo electrochemical polymerisation leading to fixed ratio copolymers of functionalised pyrrole, thiophene and furan with thiophene itself. We describe the characterisation of these polymers using FT-IR and X-ray photoelectron spectroscopies.

Here we discuss the application of X-ray photoelectron spectroscopy and absorbance–reflectance FT-IR spectroscopy to establish and quantify reactivity relationships between a range of thiophene and pyrrole monomers. In particular we investigate the application of these techniques to the characterisation of conducting polymer materials grown potentiostatically from solutions containing a binary mixture of monomers. Our data have shown that XPS is especially effective in determining polymer composition and the linear correlation between this and solution composition has enabled prescriptive synthesis of copolymer materials from the different combinations of monomers described here. This technique is much more convenient and more reliable than elemental analysis. In contrast we show that FT-IR studies, whilst providing a useful qualitative guide to the functional group content of the material, do not facilitate detailed quantitative analysis because of large intrinsic errors.

Silica particles were partially coated with silver, and a suitable chromophore, such that they could be trapped within an optical tweezers system and simultaneously be excited to emit a surface–enhanced resonance Raman scattering (SERRS) spectrum. A standard 1064 nm TEM00 mode laser was used to trap the bead whilst a frequency doubling crystal inserted into the beam gave several microwatts of 532 nm co-linear light to excite the SERRS emission. The configuration has clear applications in providing apparatus that can manipulate a particle whilst simultaneously obtaining surface sensitive sensory information.

The electrochemical polymerization of N-trimethylsilylethoxymethyl-3-methyl-4-pyrrole carboxylate ethyl ester (MPCE-SEM) in the presence of pyrrole, to give free-standing copolymer films is described. These films have been characterized by surface conductivity measurements, reflectance FTIR spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Increasing the relative concentration of MPCE-SEM in the polymerization solution resulted in an increase in the proportion of these units in the copolymer film. Increasing the proportion of MPCE-SEM units in the copolymer resulted in a decrease in surface conductivity. This is consistent with expectation because N-substituted polypyrroles tend to have lower conductivity values than unsubstituted polypyrrole. Significantly, it has also been shown that the N-protecting group of the MPCE-SEM unit can be removed after polymerization under mild conditions in a solid phase deprotection procedure. © 1998 Society of Chemical Industry

We have developed software with an interactive user interface that can be used to generate phase holograms for use with spatial light modulators. The program utilizes different hologram design techniques, allowing the user to select an appropriate algorithm. The program can be used to generate multiple beams and can be used for beam steering. We see a major application of the program to be in optical tweezers to control the position, number, and type of optical traps.