Compliant thin film model for stretchable rectangular gold thin films on elastic soft substrateWhen the gauge axis is aligned with the uniaxial strain direction, the change in resistance of the gold track of length L, width W and constant thickness t under tensile strain ε is given by:where ρ is the constant resistivity of the metal layer and υ the Poisson's ratio of PDMS. Hence :When the gauge is oriented longitudinally relative to the uniaxial strain direction, the change in resistance of the gold track of length L, width W and constant thickness t under tensile strain ε is given by:2,ax.

We design and implement a sensory skin that monitors in real time finger flexure (three sensors per finger) of a user's hand.Compared to current technologies, the electronic skin is made entirely of stretchable materials integrating silicone rubber, low resistivity liquid metal interconnects and high strain sensitivity, microstructured thin metal films. Microfabrication of the sensors combines traditional thin film process and additive manufacturing techniques. We incorporate the skin on a textile glove and demonstrate its function as an interface for finger motion and posture detection using a robotic test platform.

The electrochemical quantification of analytes in droplets of PBS separated by a fluorinated phase was investigated. PDMS-fused silica chips with pyrolysed photoresist electrodes were prepared using a simple fabrication technique...

Continuous fluidic sampling systems allow collection of brain biomarkers in vivo. Here, we propose a new sequential and intermittent sampling paradigm using droplets, called Droplet on Demand (DoD). It is implemented in a microfabricated neural probe and alternates phases of analyte removal from the tissue and phases of equilibration of the concentration in the tissue. It allows sampling droplets loaded with molecules from the brain extracellular fluid punctually, without the long transient equilibration periods typical of continuous methods. It uses an accurately defined fluidic sequence with controlled timings, volumes, and flow rates, and correct operation is verified by the embedded electrodes and a flow sensor. As a proof of concept, we demonstrated the application of this novel approach in vitro and in vivo, to collect glucose in the brain of mice, with a temporal resolution of 1–2 min and without transient regime. Absolute quantification of the glucose level in the samples was performed by direct infusion nanoelectrospray ionization Fourier transform mass spectrometry (nanoESI-FTMS). By adjusting the diffusion time and the perfusion volume of DoD, the fraction of molecules recovered in the samples can be tuned to mirror the tissue concentration at accurate points in time. Moreover, this makes quantification of biomarkers in the brain possible within acute experiments of only 20–120 min. DoD provides a complementary tool to continuous microdialysis and push–pull sampling probes. Thus, the advances allowed by DoD will benefit quantitative molecular studies in the brain, i.e., for molecules involved in volume transmission or for protein aggregates that form in neurodegenerative diseases over long periods.

A large number of lab-on-a-chip applications use fluorescence for quantifying biological entities.