A Comparison of a Novel Stretchable Smart Patch for Measuring Runner's Step Rates with Existing Measuring Technologies.

A novel wearable smart patch can monitor various aspects of physical activity, including the dynamics of running, but like any new device developed for such applications, it must first be tested for validity. Here, we compare the step rate while running in place as measured by this smart patch to the corresponding values obtained utilizing ''gold standard'' MEMS accelerometers in combination with bilateral force plates equipped with HBM load cells, as well as the values provided by a three-dimensional motion capture system and the Garmin Dynamics Running Pod. The 15 healthy, physically active volunteers (age = 23 ± 3 years; body mass = 74 ± 17 kg, height = 176 ± 10 cm) completed three consecutive 20-s bouts of running in place, starting at low, followed by medium, and finally at high intensity, all self-chosen.

Docking and Activity of DNA Polymerase on Solid-State Nanopores.

Integration of motor enzymes with biological nanopores has enabled commercial DNA sequencing technology; yet studies of the similar principle applying to solid-state nanopores are limited. Here, we demonstrate the real-life monitoring of phi29 DNA polymerase (DNAP) docking onto truncated-pyramidal nanopore (TPP) arrays through both electrical and optical readout. To achieve effective docking, atomic layer deposition of hafnium oxide is employed to reduce the narrowest pore opening size of original silicon (Si) TPPs to sub-10 nm.

Thermally controlled microfluidic back pressure regulator.

By using the temperature dependence of viscosity, we introduce a novel type of microfluidic lab-on-a-chip back pressure regulator (BPR) that can be integrated into a micro-total-analysis-system. A BPR is an important component used to gain pressure control and maintain elevated pressures in e.g.

Microfluidic active pressure and flow stabiliser.

In microfluidics, a well-known challenge is to obtain reproducible results, often constrained by unstable pressures or flow rates. Today, there are existing stabilisers made for low-pressure microfluidics or high-pressure macrofluidics, often consisting of passive membranes, which cannot stabilise long-term fluctuations. In this work, a novel stabilisation method that is able to handle high pressures in microfluidics is presented.

High-resolution particle separation by inertial focusing in high aspect ratio curved microfluidics.

The ability to focus, separate and concentrate specific targets in a fluid is essential for the analysis of complex samples such as biological fluids, where a myriad of different particles may be present. Inertial focusing is a very promising technology for such tasks, and specially a recently presented variant, inertial focusing in High Aspect Ratio Curved systems (HARC systems), where the systems are easily engineered and focus the targets together in a stable position over a wide range of particle sizes and flow rates. However, although convenient for laser interrogation and concentration, by focusing all particles together, HARC systems lose an essential feature of inertial focusing: the possibility of particle separation by size.

The upper limit and lift force within inertial focusing in high aspect ratio curved microfluidics.

Microfluidics exploiting the phenomenon of inertial focusing have attracted much attention in the last decade as they provide the means to facilitate the detection and analysis of rare particles of interest in complex fluids such as blood and natural water. Although many interesting applications have been demonstrated, the systems remain difficult to engineer. A recently presented line of the technology, inertial focusing in High Aspect Ratio Curved microfluidics, has the potential to change this and make the benefits of inertial focusing more accessible to the community.

Dynamics of DNA Clogging in Hafnium Oxide Nanopores.

Interfacing solid-state nanopores with biological systems has been exploited as a versatile analytical platform for analysis of individual biomolecules. Although clogging of solid-state nanopores due to nonspecific interactions between analytes and pore walls poses a persistent challenge in attaining the anticipated sensing efficacy, insufficient studies focus on elucidating the clogging dynamics. Herein, we investigate the DNA clogging behavior by passing double-stranded (ds) DNA molecules of different lengths through hafnium oxide(HfO)-coated silicon (Si) nanopore arrays, at different bias voltages and electrolyte pH values.

Investigation of thermal conductivity for liquid metal composites using the micromechanics-based mean-field homogenization theory.

For the facile use of liquid metal composites (LMCs) for soft, stretchable and thermal systems, it is crucial to understand and predict the thermal conductivity of the composites as a function of liquid metal (LM) volume fraction and applied strain. In this study, we investigated the effective thermal conductivity of LMCs based on various mean-field homogenization frameworks including Eshelby, Mori-Tanaka, differential and double inclusion methods. The double inclusion model turned out to make the prediction closest to the experimental results in a wide range of LM volume fractions.

Head-compliant microstrip split ring resonator for non-invasive healing monitoring after craniosynostosis-based surgery.

A soft and highly directive, proximity-coupled split-ring resonator fabricated with a liquid alloy, copper and polydimethylsiloxane (PDMS) is presented. The same was designed for sensing osteogenesis of calvarial bone. As dielectric properties of bone grafts in ossifying calvarial defects should change during the osteogenesis process, devices like this could monitor the gradual transformation of the defect into bone by differentiating changes in the dielectric properties as shifts in the resonance frequency.

On-chip background dilution in droplets with high particle recovery using acoustophoresis.

Droplet microfluidics has shown great potential for on-chip biological and chemical assays. However, fluid exchange in droplet microfluidics with high particle recovery is still a major bottleneck. Here, using acoustophoresis, we present for the first time a label-free method to achieve continuous background dilution in droplets containing cells with high sample recovery.

High-Performance Liquid Alloy Patterning of Epidermal Strain Sensors for Local Fine Skin Movement Monitoring.

Nowadays, stretchable/epidermal electronics based on liquid alloys has attracted more and more attention, and various processing techniques have subsequently been developed to demonstrate diverse applications never seen before. However, to fully exploit its potential advantages, epidermal electronics is still searching for a technique meeting all demands on resolution, pattern complexity, and operational flexibility. In this study, we propose a technique that allows for complex and high-density patterns on thin stretchable substrates by combining ultraviolet laser patterning of a modified water-soluble mask, atomized spray deposition of liquid alloys on a flexible temporary substrate, lift-off by water dissolving, and finally, component integration and encapsulation.

Inertial focusing with sub-micron resolution for separation of bacteria.

In this paper, we study inertial focusing in curved channels and demonstrate the alignment of particles with diameters between 0.5 and 2.0 μm, a range of biological relevance since it comprises a multitude of bacteria and organelles of eukaryotic cells.

Microfluidic Control Board for High-Pressure Flow, Composition, and Relative Permittivity.

Flow control is central to microfluidics and chromatography. With decreasing dimensions and high pressures, precise fluid flows are often needed. In this paper, a high-pressure flow control system is presented, allowing for the miniaturization of chromatographic systems and the increased performance of microfluidic setups by controlling flow, composition, and relative permittivity of two-component flows with CO.

Stretchable Thermoelectric Generators Metallized with Liquid Alloy.

Conventional thermoelectric generators (TEGs) are normally hard, rigid, and flat. However, most objects have curvy surfaces, which require soft and even stretchable TEGs for maximizing efficiency of thermal energy harvesting. Here, soft and stretchable TEGs using conventional rigid BiTe pellets metallized with a liquid alloy is reported.

PDMS-Based Elastomer Tuned Soft, Stretchable, and Sticky for Epidermal Electronics.

A highly soft, stretchable, and sticky polydimethylsiloxane-based elastomer is achieved by adding small fractions of an amine-based polymer. The modified elastomer is tuned with a simple mixing step and shows good processability for microstructure fabrication. The modified elastomer shows excellent compatibility with an epidermal strain sensor on human skin.

On nanopore DNA sequencing by signal and noise analysis of ionic current.

DNA sequencing, i.e., the process of determining the succession of nucleotides on a DNA strand, has become a standard aid in biomedical research and is expected to revolutionize medicine.

Capillary Self-Alignment of Microchips on Soft Substrates.

Soft micro devices and stretchable electronics have attracted great interest for their potential applications in sensory skins and wearable bio-integrated devices. One of the most important steps in building printed circuits is the alignment of assembled micro objects. Previously, the capillary self-alignment of microchips driven by surface tension effects has been shown to be able to achieve high-throughput and high-precision in the integration of micro parts on rigid hydrophilic/superhydrophobic patterned surfaces.

Mechanically Stretchable and Electrically Insulating Thermal Elastomer Composite by Liquid Alloy Droplet Embedment.

Stretchable electronics and soft robotics have shown unsurpassed features, inheriting remarkable functions from stretchable and soft materials. Electrically conductive and mechanically stretchable materials based on composites have been widely studied for stretchable electronics as electrical conductors using various combinations of materials. However, thermally tunable and stretchable materials, which have high potential in soft and stretchable thermal devices as interface or packaging materials, have not been sufficiently studied.

Self-transport and self-alignment of microchips using microscopic rain.

Alignment of microchips with receptors is an important process step in the construction of integrated micro- and nanosystems for emerging technologies, and facilitating alignment by spontaneous self-assembly processes is highly desired. Previously, capillary self-alignment of microchips driven by surface tension effects on patterned surfaces has been reported, where it was essential for microchips to have sufficient overlap with receptor sites. Here we demonstrate for the first time capillary self-transport and self-alignment of microchips, where microchips are initially placed outside the corresponding receptor sites and can be self-transported by capillary force to the receptor sites followed by self-alignment.

Influence of surface modification and static pressure on microdialysis protein extraction efficiency.

There is growing interest in using microdialysis (MD) for monitoring larger and more complex molecules such as neuropeptides and proteins. This promotes the use of MD membranes with molecular weight cut off (MWCO) of 100 kDa or above. The hydrodynamic property of the membrane goes to ultrafiltration or beyond, making the MD catheters more sensitive to pressure.

Amplified and localized photoswitching of TiO2 by micro- and nanostructuring.

Fast photoswitching of wetting properties is important for the development of micro/nanofluidic systems and lab-on-a-chip devices. Here, we show how structuring the surface amplifies photoswitching properties. Atomic layer-deposited titanium dioxide (TiO2) has phototunable hydrophilic properties due to its surface chemistry, but microscale overhang pillars and additional nanoscale topography can override the chemistry and make the surface superhydrophobic.

Tape transfer atomization patterning of liquid alloys for microfluidic stretchable wireless power transfer.

Stretchable electronics offers unsurpassed mechanical compliance on complex or soft surfaces like the human skin and organs. To fully exploit this great advantage, an autonomous system with a self-powered energy source has been sought for. Here, we present a new technology to pattern liquid alloys on soft substrates, targeting at fabrication of a hybrid-integrated power source in microfluidic stretchable electronics.

Cerebral microdialysis for protein biomarker monitoring in the neurointensive care setting - a technical approach.

Cerebral microdialysis (MD) was introduced as a neurochemical monitoring method in the early 1990s and is currently widely used for the sampling of low molecular weight molecules, signaling energy crisis, and cellular distress in the neurointensive care (NIC) setting. There is a growing interest in MD for harvesting of intracerebral protein biomarkers of secondary injury mechanisms in acute traumatic and neurovascular brain injury in the NIC community. The initial enthusiasm over the opportunity to sample protein biomarkers with high molecular weight cut-off MD catheters has dampened somewhat with the emerging realization of inherent methodological problems including protein-protein interaction, protein adhesion, and biofouling, causing an unstable in vivo performance (i.

Fluorescence imaging of macromolecule transport in high molecular weight cut-off microdialysis.

When microdialysis (MD) membrane exceeds molecular weight cut-off (MWCO) of 100 kDa, the fluid mechanics are in the ultrafiltration regime. Consequently, fluidic mass transport of macromolecules in the perfusate over the membrane may reduce the biological relevance of the sampling and cause an inflammatory response in the test subject. Therefore, a method to investigate the molecular transport of high MWCO MD is presented.