Currently, old-style personal Medicare techniques rely mostly on traditional methods, such
as cumbersome tools and complicated processes, which can be time-consuming and inconvenient
in some circumstances. Furthermore, such old methods need the use of heavy equipment, blood
draws, and traditional bench-top testing procedures. Invasive ways of acquiring test samples can
potentially cause patient discomfort and anguish. Wearable sensors, on the other hand, may be
attached to numerous body areas to capture diverse biochemical and physiological characteristics as a developing analytical tool.
Physical, chemical, and biological data transferred via the skin are used to monitor health in various circumstances. Wearable sensors can assess the aberrant conditions of the physical or chemical components of the human body in real time, exposing the body state in time, thanks to unintrusive sampling and high accuracy.
The use of conventional electronic/optoelectronic devices with human tissues can cause low signal-to-noise ratios for biosensors, because of the incomplete connection of rigid wearables with the body. The hot trend right now in wearables is flexible electronics and photonics that provide better contact with skin and the natural contours of the human body.
“This enables light-emitting and photo-detecting devices to make very good conformal contacts on soft human tissue, an important requirement for photon-based bio-signal sensing with a high signal-to-noise ratio.” Wearable devices are rapidly advancing in terms of technology, functionality and size, with more real-time applications. The disruption has already begun in health monitoring. “However, ultra-flexible and stretchable electronic devices utilize the low system modulus and the intrinsic system-level softness to solve these issues,” says Dae-Hyeong Kim, an associate professor of engineering at Seoul National University in South Korea.
The past few years have witnessed the significant impacts of wearable electronics/photonics on various aspects of our daily life, for example, healthcare monitoring and treatment, ambient monitoring, soft robotics, prosthetics, flexible display, communication, human-machine interactions, and so on. According to the development in recent years, the next-generation wearable electronics and photonics are advancing rapidly toward the era of artificial intelligence (AI) and internet of things (IoT), to achieve a higher level of comfort, convenience, connection, and intelligence.
Photonics is an important component in these devices, especially for flexible displays and wearable biosensors. Fiber optics—and optical sensors in particular—have opened doors for sensing many properties, like light intensity, vibration, temperature, pressure, strain, liquid level, pH, chemical analysis, concentration, density, and many more. But this technology is particularly useful in the medical industry, helping researchers better study viruses, toxins, tumor biomarkers, tumor cells, antibodies, and drugs.
Wearables are also becoming the latest means for medical practitioners and healthcare workers for hand-free, computationally assisted quick diagnoses and other health decision making,
through ergonomic displays and voice control features. Wearables may also be employed to create augmented reality, for reasons such as better viewing of vital organs and tissue during surgery. Wearable sensing device automation is even being employed for environmental surveillance. The capacity to simply monitor plant health, air quality, or toxins across a vast region via crowdsourcing is interesting, and certain new wearable devices make it even easier.
A team of engineers at North Carolina State University has developed an integrated, wearable system called the Health and Environmental Tracker (HET), that, they say, can monitor a user’s environment, heart rate, and other variables to predict and prevent asthma attacks. The wearable Health and Environmental Tracker (HET) aims to anticipate, for instance, an oncoming asthma attack and recommend immediate action to thwart the event. Researchers hope that eventually, most any chronic malady can be similarly addressed by such sensor-studded wearables powered by energy harvested from the patient’s own body.
Mobile Device to Provide Instant Diagnosis of Heart Disease
EU-funded CARDIS project that has developed a prototype medical device for the diagnosis of various CVDs such as arterial stenosis and heart failure. Its technology is based on silicon photonics. The press release states: “The operating principle of the device is Laser Doppler Vibrometry (LDV), in which a very low-power laser is directed towards the skin overlying an artery. The skin’s vibration amplitude and frequency, resulting from the heart beat, are extracted from the Doppler shift of the reflected beam.” It adds that the device can scan “multiple points on the skin above the artery in parallel. At the heart of the system is a silicon photonics chip containing the optical functionality of the multi-beam LDV device.”
If the results show that the technology can detect CVDs at an early stage, the project will start high-volume production. “One of the benefits of the silicon photonics technology is that at high volumes, the chip can be produced at low cost,” explains imec. The CARDIS (Early stage CARdio Vascular Disease Detection with Integrated Silicon Photonics) project was set up to design a mobile robust and low-cost device for the screening of arterial stiffness and detection of stenosis and heart failure.
A press release by project partner Interuniversitair Micro-Electronica Centrum (imec) notes that the instrument requires minimal physical contact with the patient and minimal user skills for the screening of arterial stiffness. This condition involves alterations in the mechanical properties of arteries. Much effort has focused on how best to measure this. Its assessment “by measurement of aortic pulse wave velocity (aPWV) is included in the latest guidelines for CVD risk prediction and it is a key marker for hypertension” as explained in the press release. However with currently available tools it’s difficult to screen a large number of patients for this condition at a typical general practitioner’s office.
Sleep is an integral aspect of our life to sustain our daily activity, and the quality of sleep has a massive influence on our health, work performance, and well-being. Numerous research works have shown the association between the poor quality of sleep and many adverse effects on our health including, but not limited to, obesity, diabetes, heart diseases, hypertension, mood disorders, weakened immune system, and increased mortality risk
Despite the increasing awareness of the importance of sleep, the number of people suffering from insufficient sleep has increased every year. The gold-standard sleep assessment uses polysomnography (PSG) with various sensors to identify sleep patterns and disorders. However, due to the high cost of PSG and limited availability, many people with sleep disorders are left undiagnosed.
Recent wearable sensors and electronics enable portable, continuous monitoring of sleep at home, overcoming the limitations of PSG. Low-profile wearable sensors can measure brain activity, heart activity, blood oxygen saturation, respiration, and movement.
The development of flexible and soft materials is essential for wearable electronics because of their unique chemical, electrical, and mechanical properties. Traditional materials for wearable electronics are mostly metals and semiconductors with relatively poor mechanical flexibility and stretchability. Recently, organic or polymeric materials are gaining more attention from the community due to their superior mechanical flexibility.
Physical sensing is one of the most fundamental functions required for wearable electronics to monitor different kinds of physiological signals. Several key optical technologies make such sensors possible, including e.g., optical fiber textiles, colorimetric, plasmonic, and fluorometric sensors, as well as Organic Light Emitting Diode (OLED) and Organic Photo-Diode (OPD) technologies. These emerging technologies and platforms show great promise as basic sensing elements in future wearable devices.
Researchers at the University of Texas at Dallas (Richardson, TX) and EnLiSense (Allen, TX) have developed a sensor that can be worn on your wrist or another area of the skin to monitor your glucose, cortisol, and a number of other stress and health indicators. These devices depend on Spectroscopy performed (noninvasively) on your skin rather than pricking yourself to draw blood and test your glucose levels. The device uses zinc-oxide (ZnO) thin films on nanoporous polyamide substrates to determine protein and cortisol levels in human sweat that dictate certain health conditions. As confirmed by Fourier-transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS) optical methods, the sensor is suitable for consumer applications.
Also specific to blood glucose sensing, researchers at the University of Frankfurt in Germany are using photoacoustic spectroscopy (PAS)—a combination of a windowless ultrasound between 50 and 60 kHz and an external-cavity tunable quantum-cascade laser that spans 1000 to 1245 cm-1—to obtain a mid-infrared spectrum when absorption of glucose molecules creates a sound signature that records sugar levels in skin cells.
All of these measurements depend on networks of sensors that detect and measure a multitude of physiological and electrophysiological signals. “Varying optical wavelengths are used with sensors that have algorithms for extracting useful data for accurate measurements,” says David Simpson, director of business development for mobile sensing for Integrated Device Technology in San Jose, California. Data can then be stored in skin-based non-volatile memory devices (resistive random access memory or silicon-based flash memory) or wirelessly transmitted to external smart devices (smartphones or tablet computers) via an integrated Bluetooth unit.
The optoelectronic display (or display) is an indispensable component in electronic systems as displays project information in the form of texts, images, and videos for intuitive visualization to aid human cognition. Besides OLED, another category of the active display is polymeric light-emitting devices (PLED). Compared with OLED which is based on small molecules, PLED is based on polymers and has the advantage of flexibility and large-area display.
Recently, the technology fusion of the emerging artificial intelligence (AI) with functional electronics, has nurtured a new area of intelligent systems that can detect, analyze, and make decisions with machine learning assisted algorithms. In addition, benefited from the 5G network, the acquisition rate of sensing data is able to satisfy the requirements of big data analysis and higher forms of AI.
When combining wearable electronics/photonics with AI technology, the resultant wearable systems are able to perform a more complicated and comprehensive analysis on the acquired data sets (training sets) beyond the capability of conventional approaches. Then this trained model can be used to predict the classification of the new incoming data, acting as the conditioning to trigger an intended event. The accuracy of prediction can be improved through choosing suitable algorithms, tuning the parameter of algorithms, and fusing different types of data from diversified sensors.
With the prosperous development of wearable electronics and photonics in almost every aspect of applications, electronics, and systems that can operate independently and sustainably are of great significance in the new era. As the current energy sources, that is, batteries, normally come with bulky occupation, heavy weight, rigid form, and limited lifespan, a more sustainable solution is urgently desired in the era of IoT and 5G. Benefited from the rapid development of energy harvesting and storage, wearable electronics, and systems equipped with these advanced technologies are receiving increasing attention and considered as a promising solution with potential self-sustainability. Generally speaking, piezoelectric, triboelectric, thermoelectric, and photovoltaic based energy harvesters and self-powered (ie, self-generated) sensors/actuators have excellent compatibility with wearable electronics and are thus widely adopted.
In addition to photonic wearables that monitor physical health and fitness, light can also heal. Researchers at Biomimetic Membranes and Textiles (Dübendorf, Switzerland) developed a washable, rugged photonic cloth that fights off jaundice in newborn babies by delivering blue light from LEDs into 160-μm-diameter polymer optical fibers wrapped in silk fabric. A blue-light wearable from Royal Philips (Amsterdam, Netherlands)—that has been available in Europe for several years—has received U.S. FDA approval to treat mild psoriasis. Re-Timer glasses (www.re-timer.com) manufactured in Adelaide, Australia retail for $299 and are ultrathin wearable glasses that deliver 500 nm green-blue light that the inventors say, when worn for about 60 minutes a day, can improve sleep, reduce jet lag, and allow shift workers to better manage their alertness levels during nighttime working hours
But perhaps the ultimate in photonic wearables for personal health and safety is a directionally sensitive, real-time radiation dosimeter. Proposed by researchers at La Trobe and RMIT Universities (both in Bundoora, Victoria, Australia) for individuals working with radioactive materials, the wearable uses a circular array of eight cadmium-zinc-tellurium (CdZnTe) detectors and a simple computational algorithm (performed by a small microcontroller) that can estimate the direction of a 10 microcurie (μCi) cesium-based radioactive source to within 2° in about 7 seconds.
Wearable Optical Sensor Market
Optical Sensor Market size surpassed USD 19 billion in 2019 and is expected to grow at a CAGR of over 10% between 2020 and 2026. The global optical sensor market is expected to grow at a CAGR of 11% in the forecast period of 2022-2027.
The market growth is driven by increasing uptake of optical sensors in consumer electronic devices across the globe. Consumer electronic devices, such as smartphones, tablets, and laptops, are being integrated with optical sensors for various applications such as device security, gesture recognition, and facial recognition, among others. Additionally, the rising demand for on-screen finger-print sensor technology in smartphones will further provide growth opportunities for the market.
According to Verified Market Research, the Global Wearable Sensors Market size was valued at USD 660.89 Million in 2020 and is projected to reach USD 5,208.05 Million by 2028, growing at a CAGR of 29.3% from 2021 to 2028.
Over 1/10 Americans now possess a wearable sensing gadget, such as a specialized fitness
surveillance device, a threefold increase from 2012. Fitness trackers and smartwatches
can create personalized health profiles by gathering data on the pulse, blood oxygen level,
movement, speed, step count, and even eating and sleeping patterns, using mobile phones
and cloud connections.
Such gadgets are especially appealing for at-home health surveillance, particularly for the rising number of seniors who are living independently. Wearables can offer a reliable and thorough patient health record, minimize the resource load on hospitals, and expedite the reaction time in event of an emergency by empowering older users, their families, caregivers, and Medicare professionals, through remote health surveillance capabilities. Wearable technologies for elderly health surveillance are already making an effect, with total device shipments connected to wearable technologies for elderly health surveillance expected to achieve USD 44 million in 2019.
Both electronics and photonics are important in the prospect of wearables, Optical sensors are expected to account for 13% of the wearable market by 2020, with optical and optoelectronic (OE)
tec technologies also playing a role in other market segments, for instance chemical or elastic
and pressure sensors.
The rising adoption of wearable healthcare devices in developed economies is likely to boost the optical sensor market revenue. Wearable healthcare devices, such as fit bits, pulse oximeters, smartwatches, etc., are integrated with optical sensors, providing real-time patient health monitoring solutions. These sensors offer several features such as high accuracy, compact size, and no response to electromagnetic radiation, making them ideal for applications in medical-grade wearable devices.
According to January 2020 report by Pew Research Center, about 21% of U.S. adults regularly wear smart watch or wearable fitness trackers; therefore, to address the growing demand for wearable healthcare devices, market players are introducing technically advanced products with optical sensor technology.
The major players in the market are TE Connectivity LTD., NXP Semiconductors N.V., STMicroelectronics N.V., Robert Bosch GmbH, Infineon Technologies AG, InvenSense, Inc., Knowles Electronics, LLC., Panasonic Corporation, Sensirion AG, Asahi Kasei Corporation, and Others.
Wearable Optical sensor Industry
In 2020, Maxim Integrated announced the MAXM96146, which they claim is the world’s thinnest optical sensor solution for health and fitness products. This device can illustrate some of the general concepts of optical biosensors in a concrete way. This solution, like many comparable products, is targeted toward the fitness wearable market, coming preinstalled with algorithms for activity classification, heart rate monitoring, and SpO2 monitoring. Maxim calls it a “drop-in” solution that can save up to six months to market for designers and manufacturers.
The new solution, the MAXM86416, combines Maxim’s optical biosensing analog front end, an Arm MCU, and two high sensitivity photodiodes. Aiming to build a comprehensive solution, Maxim designed the chip to include an SPI interface, two independent 19-bit ADCs, and a proprietary ambient light-cancellation circuit.
Photonics could reinvent the Apple Watch
Rockley Photonics is thought to be developing technology that could allow the Apple Watch to non-invasively track blood glucose levels. All Rockley Photonics customers are developing smartwatches like the Apple Watch or medical devices that carry out advanced biomarker detection for chronic diseases.
Rockley designs silicon photonic sensors for monitoring a person’s blood using infrared light. The company describes its technology as “significantly more accurate” than LED sensors commonly used in smart wearables. The sensors are designed to continuously, non-invasively monitor biomarkers which can usually only be tracked using specialised medical equipment, such as blood glucose and hydration levels.
Apple has been rumoured to be working on ways to add glucose monitoring to the Apple Watch. Rumours have pointed to blood glucose monitoring as a possible key feature of the Apple Watch Series 7, something that may be possible through photonics if Rockley’s claims are to be believed.
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