Engineers 3D-print personalized, wireless wearables that never need a charge

Rapid developments in material engineering, 5G and wearables are contributing to deliver health data information in real time.

Wearable sensors to monitor everything from step count to heart rate are nearly ubiquitous. But for scenarios such as measuring the onset of frailty in older adults, promptly diagnosing deadly diseases, testing the efficacy of new drugs or tracking the performance of professional athletes, medical-grade devices are needed.

University of Arizona engineers have developed a type of wearable they call a "biosymbiotic device," which has several unprecedented benefits. Not only are the devices custom 3D-printed and based on body scans of wearers, but they can operate continuously using a combination of wireless power transfer and compact energy storage. The team, led by Philipp Gutruf, assistant professor of biomedical engineering and Craig M. Berge Faculty Fellow in the College of Engineering, published its findings today in the journal Science Advances.

Current wearable sensors face various limitations. Smartwatches, for example, need to be charged, and they can only gather limited amounts of data due to their placement on the wrist. By using 3D scans of a wearer's body, which can be gathered via methods including MRIs, CT scans and even carefully combined smartphone images, Gutruf and his team can 3D-print custom-fitted devices that wrap around various body parts. Think a virtually unnoticeable, lightweight, breathable, mesh cuff designed specifically for your bicep, calf or torso. The ability to specialize sensor placement allows researchers to measure physiological parameters they otherwise couldn't.

Because these biosymbiotic devices are custom fitted to the wearer, they're also highly sensitive. Gutruf's team tested the device's ability to monitor parameters including temperature and strain while a person jumped, walked on a treadmill and used a rowing machine. In the rowing machine test, subjects wore multiple devices, tracking exercise intensity and the way muscles deformed with fine detail. The devices were accurate enough to detect body temperature changes induced by walking up a single flight of stairs.

Brain Devices

The technology can also be used to analyze brain physiology.  The brain presents several challenges.  It is behind the blood-brain barrier that prevents many substances, and medications from entering the brain fluid.  The mechanism is poorly understood.   Some sensory devices involve drilling a hole in the skull and implant a micro sensor with multiple needles that enter the brain with minimal damage to the cortex.  However this in itself creates artifacts in signals.  -

Despite the enormous efforts of clinicians and researchers, our limited insight into psychiatric disease (the worldwide-leading cause of years of life lost to death or disability) hinders the search for cures and contributes to stigmatization. Clearly, we need new answers in psychiatry. But as philosopher of science Karl Popper might have said, before we can find the answers, we need the power to ask new questions. In other words, we need new technology.

Developing appropriate techniques is difficult, however, because the mammalian brain is beyond compare in its complexity. It is an intricate system in which tens of billions of intertwined neurons—with multitudinous distinct characteristics and wiring patterns—compute with precisely timed, millisecond-scale electrical signals, as well as with a rich diversity of biochemical messengers. Because of that complexity, neuroscientists lack a deep grasp of what the brain is really doing—of how specific activity patterns within specific brain cells ultimately give rise to thoughts, feelings and memories. By extension, we also do not know how the brain's physical failures produce distinct psychiatric disorders such as depression or schizophrenia.  In other words we barely understand how the 'normal' brain works.

Tiny wireless devices

Optogenetics: Controlling the Brain with Light

In a 1979 Scientific American article Nobel laureate Francis Crick suggested that the major challenge facing neuroscience was the need to control one type of cell in the brain while leaving others unaltered. Electrical stimuli cannot meet this challenge because electrodes are too crude a tool: they stimulate all the circuitry at their insertion site without distinguishing between different cell types, and their signals cannot turn off neurons with precision. Drugs are not specific enough either, and they are much slower than the natural operating speed of the brain. Crick later speculated in lectures that light might have the properties to serve as a control tool because it could be delivered in precisely timed pulses, but at the time no one had a strategy to make specific cells responsive to light.

Meanwhile, in a realm of biology as distant from the study of the mammalian brain as might seem possible, researchers were working on microorganisms that would only much later turn out to be relevant. At least 40 years ago biologists knew that some microorganisms produce proteins that directly regulate the flow of electric charge across cell membranes in response to visible light. These proteins, which are produced by a characteristic set of "opsin" genes, help to extract energy and information from the light in the microbes' environments. You may recognize opsin from it's 'cousin' rhodopsin in the rods and cones of our retina. These  convert light energy into electrical impulses transmitted to the cerebral cortex via the optic nerves and the optic tracts to the cerebral cortex and other areas of the brain. 

Current optogenetics experiments, done in animal models, involve introducing a light-sensitive protein, which attaches to specific neurons in the brain. (delivered by viral vectors). A light stimulus is delivered to the brain with an LED under the skin or even of the surface of the skin.

Light emitting diode

The discussion of opsins goes beyond this blog I recommend reading the references at the end of the article.  It is not light reading.

Engineers 3D-print personalized, wireless wearables that never need a charge

 Optogenetic interrogation of neural circuits: technology for probing mammalian brain structures