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Collagen, it turns out, is piezoelectric; it is able to convert an applied mechanical stress to electric signals, for example when the bone is bent. Besides collagen's piezoelectricity, streaming ions also produce movement of charges, leading researchers to believe that this is the source of bone electricity. The flexure-induced current in synthetic hydroxyapatite and natural bone were remarkably similar, suggesting that flexoelectricity does indeed play a major role in generating electricity in bones. [...]because synthetic hydroxyapatite has no collagen, the quantitative similarity between the results rules out collagen piezoelectricity as a relevant contributor to the flexoelectricity of bone. [...]flexoelectricity allows a micro-crack to call for help without the need for collagen piezoelectricity or streaming ions.

News & Analysis Materials News From communications to health care to entertainment, materials research is rapidly advancing to improve the interface between humans and machines, with the aim of shrinking down wearable technology and adapting them to the contours of our bodies. Zhang, Xiao, and colleagues added silver nanoparticles during the synthesis stage to make the polymer electronically conductive, and imprinted specific patterns into the polymer melt to develop functional sensors. [...]since humidity from the air diffuses into the sensor and swells its polymer network, relative resistance changes can also track that parameter with a high accuracy (0.22 %/% RH).

Kourosh Kalantar-Zadeh, distinguished professor at RMIT University and director of the Centre for Advanced Electronics and Sensors, who is a lead researcher in this study, says, \"H2 appears in the pathway of most of the microbiome species of the gut.\" Experiments were successful in evaluating the small and large intestinal transit times. (a) Sensor-loaded capsule and the underlying sensor; (b) photo of the equipment including the phone app, capsule, and the data acquisition system.

[...]a team of researchers from Stanford University, Samsung Advanced Institute of Technology, and Gyeongsang National University has developed a scalable fabrication process to create a stretchable transistor array that could be attached to skin to monitor health, as reported in a recent issue of Nature (doi:10.1038/nature25494). \"The stretchable amplifier circuits built up by these transistors could also be utilized for the measurement of other physiological signals, including ECG, EMG, body temperature, sweat, etc.,\" says Sihong Wang from Stanford University, who is a lead author in this study. Additionally, the stretchable transistor array devices show ideal switching behavior, with no current hysteresis, minimal gate leakage, and good stability (shelf and under bias) making it viable in electronic applications.

(ProQuest: ... denotes formulae and/or non-US-ASCII text omitted; see image) News & Analysis Materials News Nacre, which comprises the inner iridescent shell layer of oysters and coats the outer layer of pearls, is an exceptionally strong material with unique and fascinating properties. Under an applied 5.0 V potential, the thin films rapidly heat up (2.6°C/min rate) and can reach temperatures as high as 150°C. The heater sustained repeated cyclic mechanical, electrical, and thermal loads without any degradation and significantly outperformed the stability limits of similar PET-based devices. \"Due to the mechanical deformability, conformability, and efficient thermal response, we envision that this flexible heater based on AgNWs embedded on a nacre-mimetic substrate will be a potential candidate in flexible wearable devices, wound dressing, or bioelectronics,\" Duan says.

Since the cross-linking density can be as low as 1 per 1000 monomers, strong bonding actually requires very little interfacial bonding. The addition of small fractions of surfactant or an increase in temperature can also provide an efficient means of reducing the total amount of silanes by concentrating them at the interface. (a-c) Polyacrylamide (PAAm) silane-modified hydrogel bound to a polydimethylsiloxane (PDMS) silane-modified elastomer along a ring. Alba Marcellan, associate professor at Sorbonne Université (ex-UPMC) in Paris and leading her research on gel adhesion and mechanics at ESPCI Paris, explains that \"based on their remarkable features of absorption, storage or release of water, gels have become essential in engineering applications like super-absorbents, soil-less agriculture, or tissue engineering.

Employing a ferroelectric film in the most commonly used solar-cell architecture of organic photovoltaics (bulk heterojunction), the researchers were able to switch the photocurrent of the device between ON and OFF states, utilizing absorbed photons as the gate. The high bandgap (3.6 eV) of the ferroelectric film means that this layer is transparent to most of the solar spectrum, ensuring that maximal photon flux reaches the sandwiched organic absorber. The next-generation designs of the solaristor could benefit from replacing the organic bulk heterojunction absorber, where the photocurrent is limited, with colloidal quantum dot or hybrid perovskite absorbers, which promise much higher photocurrents (22-30 mA cm-2).

To address this issue, the research team of Christoph Keplinger, a professor at the University of Colorado Boulder, has introduced a versatile actuation technology that combines high strains (>100%), high strength (0.3 MPa), high speed (>50 Hz), long lifetime (>1 million cycles), self-healing, and self-sensing capabilities. Exploring new approaches to design and fabricate actuation, locomotion, and sensing mechanisms for bioinspired, multifunctional, and passive robots, he points out that \"HASEL actuators can provide strains and operational bandwidths large enough for applications where mimicry of biological motion is sought.\" To exploit and further demonstrate the potential and diversity of the HASEL technology, Keplinger's research team created so-called \"Peano-HASEL\" actuators--published in Science Robotics (doi:10.1126/scirobotics.aar3276)--that can be scaled up for increased force; are able to achieve precise movements; and by using the adequate index-matching liquid, they can even be made transparent.