As the world’s population ages, the rising burdens on healthcare are driving a search for more cost-effective and practical care solutions. The costs on hospitals and trained staff are enormous. In-home healthcare aims to keep patients out of the hospital for longer whilst still providing care. This is particularly useful for the aged and those convalescing. It can also improve patient self-care, so that hospital visits are unnecessary.

Key to these developments is the growth of smart health monitoring and wearable devices. The latest devices use wireless sensors that are unobtrusive and can provide continuous real-time data. These wearable patch sensors have an influential role to play in mobile medicine.


The growth of wearable medical sensors

Some of the earliest forms of wearable technology were fitness trackers. These wrist or armbands tracked the user’s physical activity and heart rate. They often synced with smartphone apps to provide fitness feedback and advice.

The first wearable medical devices had integrated circuits on solid substrates, but these rigid packages are not an ideal match for the human body. Unreliable skin contact makes measurement uncertain. The solution is to develop wearable devices based on flexible and stretchable skin sensors.

The latest body-worn sensors are light, flexible and comfortable to wear. They can operate for long periods with built-in power supplies. Data can be stored or passed on remotely via Bluetooth to alarm systems, cloud storage or monitoring nurses and physicians. And sensors are being developed to measure biochemical analytes in addition to physiological parameters.


Moving towards healthcare

The market for flexible, wearable medical electronic products has grown in the past few years. Medical patches have been developed for continuously monitoring chronically ill patients, soldiers in combat, pilots, and premature babies, amongst other applications.

Developments include a wearable ECG monitor that can detect atrial fibrillation or measure an electrocardiogram, and send the reading to the user’s doctor. An oscillometric blood pressure monitor worn on the wrist can hold up to 100 readings in memory and transfer readings to a mobile app when it becomes available. Both of these aim to help the patient with self-monitoring, but the data can also be shared with a clinician remotely.

Biosensors represent a radical step forward in mobile health sensor technology. The introduction of chemical sensors that can measure analytes in biological fluids such as breath, sweat or saliva, creates more possibilities.

For example, there is a wide variety of metabolites and biomarkers present in sweat. The levels of chloride ions can be used to diagnose and monitor Cystic Fibrosis (CF); sodium levels can highlight electrolyte imbalance and dehydration; glucose levels can help to monitor diabetes and energy; and lactate levels can serve as an indicator of muscle fatigue. Other useful markers include cortisol, hormones and ammonium.

The sensors can be incorporated in self-adhesive patches, or be incorporated into clothing. Unlike wrist trackers or smartwatches, these wearable patches are light ,flexible and convenient.

The wearable healthcare technology market is surging, with one analysis suggesting that the total installed base of fitness tracker and health-based wearables in the US is growing by 10% annually.

smartphone and traditional residential phone

Evolution of wearable patch sensors

At the end of 2019, the Medical International Trade Show in Dusseldorf brought together forty exhibitors presenting wearable technologies. In addition to performance monitoring devices for sports and fitness, there were smart plasters for asthma, intelligent shoe soles for the early detection of diabetes, and solutions for Parkinson’s patients.

For rehabilitation, there were portable sensors for knee and hand rehabilitation and a variety of motion sensors. And mobile monitoring of vital data included heart rate, temperature, respiration, stress, oxygen saturation, intelligent care patches and fall detection. One company demonstrated a shirt that provided continuous ECG monitoring. While it had the look and feel of a normal casual shirt and allowed the patient to move freely, it could monitor the heart via five electrodes without the need for any cables or external batteries.

The next generation of wearable electronics employs novel materials that are flexible, cheap, transparent and conduct electricity. These flexible and stretchable conductors can be printed or woven into fabrics or fabricated onto flexible plastic substrates. Applications in the consumer world, such as flexible smartphones, are likely to accelerate their development and drive down costs.

A related development is smart clothing, or e-textiles, which leverage sensors embedded in your shirt or socks for biometric monitoring.

Thin bendable and foldable batteries and capacitors are being developed as power sources for these wearable devices. Conduction is possible through electronic inks using metal nanoparticles. Smart inks and coatings also have applications in intelligent packaging and smart clothing.

Potentiometric ion sensors can be used to measure a broad range of analytes, whose presence produces a change in conductivity. Conducting polymers and carbon nanomaterials are some of the materials widely used for these ion sensors.


Latest developments

The technologies mentioned above are still in development, and companies such as Abbott, Samsung, DuPont, Hitachi, LG and Panasonic are active in the field. Whilst the value of physical sensors is relatively well established, work continues to improve the stability, resiliency and biocompatibility of biosensors. Nevertheless, medical sensors leveraging new flexible materials are being introduced at an accelerating pace.

Gel-covered wireless sensors have been developed to monitor infants’ vital signs, such as heart rate, skin temperature and respiration rate. They are embedded in flexible electronic patches and send data via wireless connections to a smartphone or tablet. These inconspicuous sensors allow parents to have more skin-to-skin contact with their newborns.

A sweat sensor using a breathable natural polymer interface with the underlying skin allows sweat to travel through for electrochemical analysis using printed electrodes. The sensors are less than 2 cm long. The electrodes are printed onto the polymer membrane, and oxidation-reduction reactions produce an electrical signal that measures the concentration of the metabolite of interest. The device can measure biomarkers including glucose, lactic acid, potassium, and sodium. Hormone monitoring is also being considered.

Another device uses conductive threads placed directly on the fabric gauze of a commercial bandage to form a patch sensor. Threads are coated so as to respond to a particular biomarker. The array of thread sensors can be integrated into a patch or clothing, and connected to circuitry which can send data to a smartphone wirelessly. By using threads with specific coatings, the device can track several biomarkers at the same time.


Wearable Software with Fluffy Spider

Fluffy Spider Technologies is at the forefront of the “Digitization of Health” surge.

We create commercially viable systems for sensor technology that manage the ongoing data feed from the sensor’s local storage to a permanent location, such as the Cloud, where the data is integrated with electronic health and medical records.

High quality commercial software requires a dedicated team that has the relevant experience. We can work with you through the entire process, from concept to commercialisation.

If you would like to learn more about our capabilities and solutions, please get in touch.