In recent years, we have witnessed a rapid surge in assisted living technologies due to a rapidly aging society. The aging population, the increasing cost of formal health care, the caregiver burden, and the importance that the individuals place on living independently, all motivate development of innovative-assisted living technologies for safe and independent aging. In this survey, we will summarize the emergence of `ambient-assisted living” (AAL) tools for older adults based on ambient intelligence paradigm. We will summarize the state-of-the-art AAL technologies, tools, and techniques, and we will look at current and future challenges.

A Survey on Ambient-Assisted Living Tools for Older Adults

A review of stimuli-responsive shape memory polymer composites

Biomedical engineers have traditionally developed technologies in response to the needs of the developed world's medical community. As a result, the diagnostic systems on which they have worked have met the requirements of well-funded laboratories in highly regulated and quality-assessed environments. However, such approaches do not address the needs of the majority of the world's people afflicted with infectious diseases, who have, at best, access to poorly resourced health care facilities with almost no supporting clinical laboratory infrastructure. A major challenge for the biomedical engineering community is to develop diagnostic tests to meet the needs of these people, the majority of whom are in the developing world. We here review the context in which the diagnostics must operate, some of the appropriate diagnostic technologies already in distribution, and some emerging technologies that promise to address this challenge. However, there is much room for innovation, adaptation, and cost reduction be...

https://www.annualreviews.org/doi/pdf/10.1146/annurev.bioeng.10.061807.160524

Point-of-care diagnostics for global health.

Micro total analysis systems. Recent developments.

The realization of miniaturized optofluidic platforms offers potential for achieving more functional and more compact devices. Such integrated systems bring fluid and light together and exploit their microscale interaction for a large variety of applications. The high sensitivity of compact microphotonic devices can generate effective microfluidic sensors, with integration capabilities. By turning the technology around, the exploitation of fluid properties holds the promise of highly flexible, tunable or reconfigurable microphotonic devices. We overview some of the exciting developments so far.

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Integrated optofluidics: A new river of light

A microchip-based flow confinement method for rapid delivery of small sample volumes to sensor surfaces is described. For flow confinement, a sample flow is joined with a perpendicular makeup flow of water or sample medium. Under laminar flow conditions, the makeup flow confines the sample into a thin layer above the sensing area and increases its velocity. This can benefit mass transport limited processes such as DNA hybridization or heterogeneous immunoassays. For proof of concept, this method was applied to a high-affinity immunoassay with excess capture antibody. Rabbit IgG was immobilized onto a silicon nitride waveguide. Cy5-labeled anti-rabbit IgG was hydrodynamically pumped over the immobilized zone through an attached 3D-PDMS flow cell with 20-μm-deep microchannels. The degree of confinement was adjusted through the volume flow rate of the confining flow. Evanescent field-based fluorescence detection enabled monitoring of the binding event. Assays were allowed to reach equilibrium to enable senso...

Three-Dimensional Microfluidic Confinement for Efficient Sample Delivery to Biosensor Surfaces. Application to Immunoassays on Planar Optical Waveguides

One-step 3D shaping using a gray-tone mask for optical and microelectronic applications

A bio-chemical sensor system based on wavelength interrogation of integrated optical sensor chips is presented. The combination of a non-mechanical scanning approach with sensor chips of high quality and stability allows fast and accurate multi-channel measurements. The emphasis of the present paper lies in presenting detailed design considerations, and in reporting the application of the system to several high sensitivity sensing tasks. An excellent performance of the sensor is demonstrated for bulk refractometry and affinity measurements. The bulk refractometric measurements show a detection limit of

Label-free highly sensitive detection of (small) molecules by wavelength interrogation of integrated optical chips

Cellulose nanocrystals (CNCs), which offer a high aspect ratio, large specific surface area, and large number of reactive surface groups, are well suited for the facile immobilization of high density biological probes. We here report functional high surface area scaffolds based on cellulose nanocrystals (CNCs) and poly(vinyl alcohol) (PVA) and demonstrate that this platform is useful for fluorescence-based sensing schemes. Porous CNC/PVA nanocomposite films with a thickness of 25-70 nm were deposited on glass substrates by dip-coating with an aqueous mixture of the CNCs and PVA, and the porous nanostructure was fixated by heat treatment. In a subsequent step, a portion of the scaffold's hydroxyl surface groups was reacted with 2-(acryloxy)ethyl (3-isocyanato-4-methylphenyl)carbamate to permit the immobilization of thiolated fluorescein-substituted lysine, which was used as a first sensing motif, via nucleophile-based thiol-ene Michael addition. The resulting sensor films exhibit a nearly instantaneous and pronounced change of their fluorescence emission intensity in response to changes in pH. The approach was further extended to the detection of protease activity by immobilizing a Forster-type resonance energy transfer chromophore pair via a labile peptide sequence to the scaffold. This sensing scheme is based on the degradation of the protein linker in the presence of appropriate enzymes, which separate the chromophores and causes a turn-on of the originally quenched fluorescence. Using a standard benchtop spectrometer to monitor the increase in fluorescence intensity, trypsin was detected at a concentration of 250 μg/mL, i.e., in a concentration that is typical for abnormal proteolytic activity in wound fluids.

Biosensors Based on Porous Cellulose Nanocrystal–Poly(vinyl Alcohol) Scaffolds

A pH sensor based on polymethylmethacrylate (PMMA) optical fibers has been developed for on-body monitoring in biological fluids. Detection relies on evanescent wave absorption in a thin film deposited on the fiber core. The sensitive film was prepared using sol–gel technology from a mixture of tetraethyl orthosilicate (TEOS) and methyltriethoxysilane (MTES) or phenyltriethoxysilane (PTES), forming a porous hybrid organic–inorganic layer upon drying. The so-called ORMOSILs (organically modified silicate) were doped with bromophenol blue (BB) and the formulation was optimized to suppress dye leaching by varying the fraction of organic precursor, the sol aging time and the drying conditions. The molecular structure of the films was examined by Fourier-transformed infrared (FTIR) spectroscopy, and their optical responses characterized with UV–VIS absorption spectroscopy. Homogeneous crack-free films were obtained with an optimal MTES content of 50%. Leaching from these films was greatly reduced, with more than 80% of dyes remaining after 2 months in phosphate buffered saline (PBS) buffer. The entrapped indicator showed pronounced increase of apparent pKa and a broader response range compared to the free form in solution. The sensor demonstrated good sensitivity from pH 3 to 9, with an optical signal variation of 3.5 dB. It showed sensitivity to ionic strength variations, but not to temperature in the range between 20 and 50 °C. Reversible pH monitoring between pH 5 and 8 with a precision of 0.2 pH unit was demonstrated in human serum as a model biological fluid, without degradation of the sensing fiber over 24 h. This simple and low cost device will be particularly valuable to support diagnosis and the evaluation of therapies for wound healing.

Guy Voirin

Papers

Three-Dimensional Microfluidic Confinement for Efficient Sample Delivery to Biosensor Surfaces. Application to Immunoassays on Planar Optical Waveguides

One-step 3D shaping using a gray-tone mask for optical and microelectronic applications

Label-free highly sensitive detection of (small) molecules by wavelength interrogation of integrated optical chips

Biosensors Based on Porous Cellulose Nanocrystal–Poly(vinyl Alcohol) Scaffolds

Development of a polymer optical fiber pH sensor for on-body monitoring application