A wearable fluidic collection patch and ion chromatography method for sweat electrolyte monitoring during exercise.

This paper presents a method to continuously collect and reliably measure sweat analyte concentrations during exercise. The method can be used to validate newly developed sweat sensors and to obtain insight into intraindividual variations of sweat analytes in athletes. First, a novel design of a sweat collection system is created. The sweat collection patch, that is made from hydrophilized foil and a double-sided acrylate adhesive, consists of a reservoir array that collects samples consecutively in time. During a physiological experiment, sweat can be collected from the back of a participant and the filling speed of the collector is monitored by using a camera. After the experiment, Na+, Cl- and K+ levels are measured with ion chromatography. Sweat analyte variations are measured during exercise for an hour at three different locations on the back. The Na+ and Cl- variations show a similar trend and the absolute concentrations vary with the patch location. Na+ and Cl- concentrations increase and K+ concentrations seem to decrease during this exercise. With this new sweat collection system, sweat Na+, Cl- and K+ concentrations can be collected over time during exercise at medium to high intensity, to analyse the trend in electrolyte variations per individual.

Miniature 10 kHz thermo-optic delay line in silicon.

The scanning delay line is a key component of time-domain optical coherence tomography systems. It has evolved since its inception toward higher scan rates and simpler implementation. However, existing approaches still suffer from drawbacks in terms of size, cost, and complexity, and they are not suitable for implementation using integrated optics. In this Letter, we report a rapid scanning delay line based on the thermo-optic effect of silicon at λ = 1.3 µm manufactured around a generic planar lightwave circuit technology. The reported device attained line scan rates of 10 kHz and demonstrated a scan range of 0.95 mm without suffering any observable loss of resolution (15 µm FWHM) owing to depth-dependent chromatic dispersion.

Time-domain Optical Coherence Tomography system with integrated delay line for surgical guidance applications.

Optical Coherence Tomography is a high resolution imaging technique able to provide in-depth information about living tissue. Among all its applications, it can be argued that surgical guidance is one of the most demanding in terms of system reliability, footprint and cost. In order to enable faster adoption of this technology in that field, we had already developed and demonstrated a new type of scanning delay line based on the thermo-optic effect of silicon. By changing the temperature of an integrated waveguide, we are able to produce a variation in optical delay. In this paper, we demonstrate the inclusion of such a device in a complete system and the performance levels that can be achieved with this technique. In particular, we show a line scan rate of 2kHz with good linearity and a scan range of 0.95mm in air. These values meet the needs of most surgical guidance applications.

A telemetric light delivery system for metronomic photodynamic therapy (mPDT) in rats.

Light delivery and monitoring during photodynamic therapy (PDT) is often limited by the need for a physical link between the light source, detectors and the treatment volume. This paper reports on the first in vivo experiments performed with a fully implantable telemetric system, designed for a rat glioblastoma model. In this system, light delivery is performed using a solid state optode containing 2 LEDs, and 4 photodiodes which will be used to monitor light delivery in future experiments. Powering and communication is achieved by means of an inductive link. The implant may remain in the animal for extended time periods, making it particularly interesting for performing metronomic PDT. In this paper, we demonstrate the feasibility of in vivo light delivery and biocompatibility of the device.. Activation of the inductive link as well as illumination of the brain by the LED did not influence animal behavior during or after treatment. We show that the implant can remain in the animal for two weeks without causing serious biological reactions.

Shape based Monte Carlo code for light transport in complex heterogeneous Tissues.

A Monte Carlo code for the calculation of light transport in heterogeneous scattering media is presented together with its validation. Triangle meshes are used to define the interfaces between different materials, in contrast with techniques based on individual volume elements. This approach allows to address realistic problems in a flexible way. A hierarchical spatial organisation enables a fast photon-surface intersection test. The application of the new environment to evaluate the impact of the trabecular structure of bone on its optical properties is demonstrated. A model of the trabecular micro structure recovered from microCT data was used to compute light distribution within tissue. Time-resolved curves across a spherical bone volume were computed. The work presented enables simulation of radiative transport in complex reality-based models of tissue and serves as a powerful, generic tool to study the effect of heterogeneity in the field of biomedical optics.