*Researchers unveil heart monitor powered by sunlight

Delaying pregnancy may increase the risk of cardiovascular disease in both women and their children, with boys at higher risk of disease, according to a new study. Researchers from the University of Alberta in Canada presented their findings Tuesday at the American Physiological Society’s (APS) Cardiovascular, Renal and Metabolic Diseases: Sex-Specific Implications for Physiology conference in Knoxville, Tennesse, United States (U.S.).

The study was published in Science Daily.
Previous studies have found that advanced maternal age — 35 or older during pregnancy — increases the risk of impaired blood vessel function and reduced blood flow to the placenta. These issues endanger the growth and overall health of the unborn child and may contribute to heart disease later in the pregnant woman’s life. Researchers grouped a rat model of advanced maternal age according to pregnancy status, including “never pregnant,” “postpartum” and “pregnancy loss.”

They found the pregnancy loss group had less widening of the blood vessels (vasodilation) compared to the groups that were never pregnant or had recently delivered. In some cases, less vasodilation may lead to decreased vascular health. In addition, the postpartum group had reduced vasodilation in the arteries of the intestines. “These data demonstrate mechanisms which may lead to worsened outcomes at an advanced maternal age, including early pregnancy termination, and later life cardiovascular dysfunction,” the research team wrote.

The researchers also found sex-specific differences in health risks of the older rats’ offspring. Males born to the postpartum group had impaired function of the blood vessel lining and cardiac risk factors associated with interrupted blood flow. The female offspring did not show the same risk factors. “Given the increasing trend toward delaying pregnancy, our findings have significant population and health care implications and further illustrate pregnancy as a window of opportunity to assess cardiovascular health,” the researchers wrote.

Meanwhile, scientists have developed a human-friendly, ultra-flexible organic sensor powered by sunlight, which acts as a self-powered heart monitor. Previously, they developed a flexible photovoltaic cell that could be incorporated into textiles. In this study, they directly integrated a sensory device, called an organic electrochemical transistor — a type of electronic device that can be used to measure a variety of biological functions — into a flexible organic solar cell. Using it, they were then able to measure the heartbeats of rats and humans under bright light conditions.

Self-powered devices that can be fit directly on human skin or tissue have great potential for medical applications. They could be used as physiological sensors for the real-time monitoring of heart or brain function in the human body. However, practical realization has been impractical due to the bulkiness of batteries and insufficient power supply, or due to noise interference from the electrical supply, impeding conformability and long-term operation.

The key requirement for such devices is a stable and adequate energy supply. A key advance in this study, published in Nature, is the use of a nano-grating surface on the light absorbers of the solar cell, allowing for high photo-conversion efficiency (PCE) and light angle independency. Thanks to this, the researchers were able to achieve a PCE of 10.5 percent and a high power-per-weight ratio of 11.46 watts per gram, approaching the “magic number” of 15 percent that will make organic photovoltaics competitive with their silicon-based counterparts. They demonstrated a PCE decrease of only 25 percent (from 9.82 per cent to 7.33 per cent) under repetitive compression test (900 cycles) and a higher PCE gain of 45 percent compared to non-grating devices under 60 degree light angle.

To demonstrate a practical application, sensory devices called organic electrochemical transistors were integrated with organic solar cells on an ultra-thin substrate, to allow the self-powered detection of heartbeats either on the skin or to record electrocardiographic (ECG) signals directly on the heart of a rat. They found that the device worked well at a lighting level of 10,000 lux, which is equivalent to the light seen when one is in the shade on a clear sunny day, and experienced less noise than similar devices connected to a battery, presumably because of the lack of electric wires.

According to Kenjiro Fukuda of the RIKEN Center for Emergent Matter Science, “This is a nice step forward in the quest to make self-powered medical monitoring devices that can be placed on human tissue. There are some important remaining tasks, such as the development of flexible power storage devices, and we will continue to collaborate with other groups to produce practical devices. Importantly, for the current experiments we worked on the analog part of our device, which powers the device and conducts the measurement. There is also a digital silicon-based portion, for the transmission of data, and further work in that area will also help to make such devices practical.” The research was carried out by RIKEN in collaboration with researchers from the University of Tokyo.

Guardian

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