ROCS microscopy with distinct zero-order blocking.

Research in modern light microscopy continuously seeks to improve spatial and temporal resolution in combination with user-friendly, cost-effective imaging systems. Among different label-free imaging approaches, Rotating Coherent Scattering (ROCS) microscopy in darkfield mode achieves superior resolution and contrast without image reconstructions, which is especially helpful in life cell experiments. Here we demonstrate how to achieve 145 nm resolution with an amplitude transmission mask for spatial filtering.

100 Hz ROCS microscopy correlated with fluorescence reveals cellular dynamics on different spatiotemporal scales.

Fluorescence techniques dominate the field of live-cell microscopy, but bleaching and motion blur from too long integration times limit dynamic investigations of small objects. High contrast, label-free life-cell imaging of thousands of acquisitions at 160 nm resolution and 100 Hz is possible by Rotating Coherent Scattering (ROCS) microscopy, where intensity speckle patterns from all azimuthal illumination directions are added up within 10 ms. In combination with fluorescence, we demonstrate the performance of improved Total Internal Reflection (TIR)-ROCS with variable illumination including timescale decomposition and activity mapping at five different examples: millisecond reorganization of macrophage actin cortex structures, fast degranulation and pore opening in mast cells, nanotube dynamics between cardiomyocytes and fibroblasts, thermal noise driven binding behavior of virus-sized particles at cells, and, bacterial lectin dynamics at the cortex of lung cells.

Photonic sensing of arterial distension.

Most cardiovascular diseases, such as arteriosclerosis and hypertension, are directly linked to pathological changes in hemodynamics, i.e. the complex coupling of blood pressure, blood flow and arterial distension.

Implantable pulse oximetry on subcutaneous tissue.

Blood oxygen saturation is one of the most prominent measurement parameters in daily clinical routine. However up to now, it is not possible to continuously monitor this parameter reliably in mobile patients. High-risk patients suffering from cardiovascular diseases could benefit from long-term monitoring of blood oxygen saturation.

Implantable impedance plethysmography.

We demonstrate by theory, as well as by ex vivo and in vivo measurements that impedance plethysmography, applied extravascularly directly on large arteries, is a viable method for monitoring various cardiovascular parameters, such as blood pressure, with high accuracy. The sensor is designed as an implant to monitor cardiac events and arteriosclerotic progression over the long term.

Magnetic sensor for arterial distension and blood pressure monitoring.

A novel sensor for measuring arterial distension, pulse and pressure waveform is developed and evaluated. The system consists of a magnetic sensor which is applied and fixed to arterial vessels without any blood vessel constriction, hence avoiding stenosis. The measurement principle could be validated by in vitro experiments on silicone tubes, and by in vivo experiments in an animal model, thereby indicating the non-linear viscoelastic characteristics of real blood vessels.

Radiative transport in large arteries.

A refined model for the photon energy distribution in a living artery is established by solving the radiative transfer equation in a cylindrical geometry, using the Monte Carlo method. Combining this model with the most recent experimental values for the optical properties of flowing blood and the biomechanics of a blood-filled artery subject to a pulsatile pressure, we find that the optical intensity transmitted through large arteries decreases linearly with increasing arterial distension. This finding provides a solid theoretical foundation for measuring photoplethysmograms.

Stretchable optoelectronic circuits embedded in a polymer network.

Stretchable optoelectronic circuits, incorporating chip-level LEDs and photodiodes in a silicone membrane, are demonstrated. Due to its highly miniaturized design and tissue-like mechanical properties, such an optical circuit can be conformally applied to the epidermis and be used for measurement of photoplethysmograms. This level of optical functionality in a stretchable substrate is potentially of great interest for personal health monitoring.

Implantable acceleration plethysmography for blood pressure determination.

This paper presents an implantable accelerometer which detects plethysmograms directly at an artery. The sensor provides a new method for continuous blood pressure monitoring. In vivo measurements indicate that the accelerometer is well suited for determining the Pulse Transit Time (PTT) and the Reflected Wave Transit Time (RWTT).

Lock-in amplification for implantable multiwavelength pulse oximeters.

Standard as well as multiwavelength pulse oximetry as established methods for measuring blood oxygen saturation or fractions of dyshemoglobins suffer from different kinds of interference and noise. Employing lock-in technique as a read-out approach for multiwavelength pulse oximetry is proposed here and strongly decreases such signal disturbance. An analog lock-in amplifier was designed to modulate multiple LEDs simultaneously and to separate the signals detected by a single photodiode.

Subcutaneous blood pressure monitoring with an implantable optical sensor.

We introduce a minimally invasive, implantable system that uses pulse transit time to determine blood pressure. In contrast to previous approaches, the pulse wave is detected by a photoplethysmographic (PPG) signal, acquired with high quality directly on subcutaneous muscle tissue. Electrocardiograms (ECG) were measured with flexible, implantable electrodes on the same tissue.

Determination of vessel wall dynamics by optical microsensors.

Spectralphotometric measurement methods as, for example, pulse oximetry are established approaches for extracorporeal determination of blood constituents. We measure the dynamics of the arterial distension intracorporeally thus extending the scope of the method substantially. A miniaturized opto-electronic sensor is attached directly to larger arteries without harming the vessel.

Arterial strain measurement by implantable capacitive sensor without vessel constriction.

Cardiovascular disease caused 32.8% of deaths in the United States in 2008 [1]. The most important medical parameter is the arterial blood pressure.

An implantable optical blood pressure sensor based on pulse transit time.

An implantable sensor system for long-term monitoring of blood pressure is realized by taking advantage of the correlation between pulse transit time and blood pressure. The highly integrated implantable sensor module, fabricated using MEMS technologies, uses 8 light emitting diodes (LEDs) and a photodetector on chip level. The sensor is applied to large blood vessels, such as the carotid or femoral arteries, and allows extravascular measurement of highly-resolved photoplethysmograms.

Wavelet based data analysis for implantable pulse oximetric sensors.

Cardiovascular data recording by implantable sensor modules exhibits a number of advantages over extra-corporeal standard approaches. Implantable sensors feature their benefits in particular for high risk patients suffering from chronic heart diseases, because diagnosis can be combined with therapy in a closed loop system. Nevertheless, the measured photoplethysmographic signals reveal different kinds of noise and artifacts.

Fast parallel interferometric 3D tracking of numerous optically trapped particles and their hydrodynamic interaction.

Multi-dimensional, correlated particle tracking is a key technology to reveal dynamic processes in living and synthetic soft matter systems. In this paper we present a new method for tracking micron-sized beads in parallel and in all three dimensions - faster and more precise than existing techniques. Using an acousto-optic deflector and two quadrant-photo-diodes, we can track numerous optically trapped beads at up to tens of kHz with a precision of a few nanometers by back-focal plane interferometry.