Depth resolution of Piezoresponse force microscopy

Given that a ferroelectric domain is generally a three dimensional entity, the determination of its area as well as its depth is mandatory for full characterization. Piezoresponse force microscopy (PFM) is known for its ability to map the lateral dimensions of ferroelectric domains with high accuracy. However, no depth profile information has been readily available so far. Here, we have used ferroelectric domains of known depth profile to determine the dependence of the PFM response on the depth of the domain, and thus effectively the depth resolution of PFM detection

Rapid multiplexed detection on lateral-flow devices using a laser direct-write technique

Paper-based lateral flow devices (LFDs) are regarded as ideal low-cost diagnostic solutions for point-of-care (POC) scenarios that allow rapid detection of a single analyte within a fluidic sample, and have been in common use for a decade. In recent years, there has been an increasing need for rapid and simultaneous detection of multiple analytes present within a single sample and to facilitate this, we report here a novel solution—detection using a multi-path LFD created via the precise partitioning of the single flow-path of a standard LFD using our previously reported laser direct-write (LDW) technique. The multiple flow-paths allow the simultaneous detection of the different analytes individually within each of the parallel channels without any cross-reactivity. The appearance of coloured test lines in individual channels indicates the presence of the different analytes within a sample. We successfully present the use of a LDW-patterned multi-path LFD for multiplexed detection of a biomarker panel comprising C-reactive protein (CRP) and Serum amyloid A-1 (SAA1), used for the diagnosis of bacterial infections. Overall, we demonstrate the use of our LDW technique in the creation of a novel LFD that enables multiplexed detection of two inflammation markers within a single LFD providing a detection protocol that is comparatively more efficient than the standard sequential multiplexing procedure

Dataset for Rapid multiplexed detection on later-flow devices using a laser direct-write technique

Data for paper : He, P., Katis, I., Eason, R., &amp; Sones, C. L. (2018). Rapid Multiplexed Detection on Lateral-Flow Devices Using a Laser Direct-Write Technique. DOI: 10.3390/bios8040097</span

Electro-optic solid state beam deflection: resolution considerations and 2-D implementation

A simpler, alternative to 'prism type' electro-optic (EO) solid state deflectors has been recently demonstrated. This device is essentially a single interface version of a conventional deflector, but significant deflection is achieved by setting the input beam at grazing incidence to the interface (where, additionally, it can act as an EO switch). The increased deflection seen near TIR is, however, made at the expense of increased divergence of the output beam. Overall deflection can be a misleading quantity to determine the performance of a deflector as this could always be increased with suitable lenses. A more reliable figure of merit is the number of separate resolvable spots that can be imaged from the deflector output. Here we analyze the achievable resolution for a single interface deflector. It can be seen that with a suitably sized device, significant resolution can be attained from a single interface deflector as shown in Fig.1. The resolution is shown here as a function of temperature since if the deflector were to be working at visible wavelengths if would necessarily be heated to avoid photo-refractive effects. Additionally heating has a secondary role in increasing resolution due to the intrinsic n term in the EO equation. Although there are still issues to overcome in terms of the output beam quality of a single interface deflector, it does possess one major advantage over the previous, multiple interface deflectors. Due to its simplicity it can be fashioned to function in 2 dimensions (Fig.2). This would be the first ever report to our knowledge of a 2D EO solid state beam deflector

Laser-based patterning for fluidic devices in nitrocellulose

In this report, we demonstrate a simple and low cost method that can be reproducibly used for fabrication of microfluidic devices in nitrocellulose. The fluidic patterns are created via a laser-based direct-write technique that induces polymerisation of a photo-polymer previously impregnated in the nitrocellulose. The resulting structures form hydrophobic barriers that extend through the thickness of the nitrocellulose and define an interconnected hydrophilic fluidic-flow pattern. Our experimental results show that using this method it is possible to achieve microfluidic channels with lateral dimensions of ~100µm using hydrophobic barriers that form the channel walls with dimensions of ~60µm; both of these values are considerably smaller than those that can be achieved with other current techniques used in the fabrication of nitrocellulose-based fluidic devices. A simple grid patterned nitrocellulose device was then used for the detection of C-reactive protein via a sandwich enzyme-linked immunosorbent assay, which served as a useful proof-of-principle experiment

Domain manipulation with a light touch: light assisted poling in ferroelectrics

Contents of talk: 1. Ferroelectric materials and domains2. Domain manipulation (poling)3. Light assisted poling (LAP)4. All optical poling (AOP)    Regular periodic arrays v. random self-organisation.5. Latent poling:6. Mechanisms and conclusion

Polymer-coated compliant receivers for intact laser-induced forward transfer of thin films: experimental results and modelling

In this study, we investigate both experimentally and numerically laser-induced forward transfer (LIFT) of thin films to determine the role of a thin polymer layer coating the receiver with the aim of modifying the rate of deceleration and reduction of material stress preventing intact material transfer. A numerical model of the impact phase during LIFT shows that such a layer reduces the modelled stress. The evolution of stress within the transferred deposit and the substrate as a function of the thickness of the polymer layer, the transfer velocity and the elastic properties of the polymer are evaluated. The functionality of the polymer layer is verified experimentally by LIFT printing intact 1µm-thick bismuth telluride films and polymeric light-emitting diode pads onto a layer of 12µm-thick polydimethylsiloxane and 50-nm-thick poly(3,4-ethylenedioxythiophene) blended with poly(styrenesulfonate) (PEDOT:PSS), respectively. Furthermore, it is demonstrated experimentally that the introduction of such a compliant layer improves adhesion between the deposit and its substrate

UV laser radiation inhibits domain inversion in lithium niobate

Continuous wave UV laser (λ=244 nm) irradiation of the +z face of lithium niobate single crystals inhibits ferroelectric domain inversion in the volume of the crystal which lies immediately below the UV exposed surface

Differential etch rates in z-cut LiNbO₃ for variable HF/HNO₃ concentrations

We report the experimental measurements for etch rates of the +z and -z faces of single crystal lithium niobate immersed in HF and HNO3 acid mixtures of varying ratios. We find that pure HF produces an etch rate that is a factor of 2 higher than the rate obtained for the more frequently used mixture of HF/HNO3 in a 1:2 ratio. We further observe that the quality of etching is improved for either pure HF or HF/HNO3 in a 1:4 ratio, again by comparison with use of a 1 : 2 ratio. These results lead to a discussion of the etch chemistry involved, and an explanation for the observed high degree of differential etching between the +z and -z crystal faces

Paper-based colorimetric enzyme linked immunosorbent assay fabricated by laser induced forward transfer

We report the Laser Induced Forward Transfer (LIFT) of antibodies from a liquid donor film onto paper receivers for application as point-of-care diagnostic sensors. To minimise the loss of functionality of the active biomolecules during transfer, a dynamic release layer was employed to shield the biomaterial from direct exposure to the pulsed laser source. Cellulose paper was chosen as the ideal receiver because of its inherent bio-compatibility, liquid transport properties, wide availability and low cost, all of which make it an efficient and suitable platform for point-of-care diagnostic sensors. Both enzyme-tagged and untagged IgG antibodies were LIFT-printed and their functionality was confirmed via a colorimetric enzyme-linked immunosorbent assay. Localisation of the printed antibodies was exhibited, which can allow the creation of complex 2-d patterns such as QR codes or letters for use in a final working device. Finally, a calibration curve was determined that related the intensity of the colour obtained to the concentration of active antibodies to enable quantitative assessment of the device performance. The motivation for this work was to implement a laser-based procedure for manufacturing low-cost, point-of-care diagnostic devices on paper