Wearable electrode material for long-term EKG monitoring

The use of wearable devices for health and wellness monitoring is rapidly growing. Over the past decade, wearable technology has gained acceptance from consumers and increased investment from the tech industry. For many years, wearable devices have offered basic features such as step count. However, over time these features have evolved to offer more advanced physiological measurements such as heart electrical activity.

Electrocardiogram (ECG/EKG) monitoring is becoming one of the most attractive health-related features of modern smartwatches, and with cardiovascular disease (CVD) one of the leading causes of deaths worldwide, the use of smartwatches to remotely monitor patients could greatly improve the ongoing care of heart injury.

Despite the increase in interest, the production of accurate and high quality ECG/EKG devices fit for consumer use has been difficult for many product manufactures and industries.

The development cycle can be complex, requiring expertise across the full signal chain: the electrodes, the hardware, the signal filtering and the algorithms. Each of these areas have their own unique challenges. There are many variables within the signal chain and managing all of these effectively is paramount.

Dry Electrode challenges in EKG development
To detect EKG, electrodes are required on a device. This sensing interface is a critical component in enabling the accuracy that will be required, but it’s also the one that can be most difficult to implement, especially when using dry electrodes (a common requirement for consumer devices due to aesthetic requirements, ease of use and need to remove conductive gel requirements).

When working at the electrode stage of the EKG development cycle, there are many challenges including electrode material choice, physical design, the characteristics of the skin location, aesthetic requirements as well as meeting the overall performance requirements of the end device. On a system level, the performance of some of these challenges can be mitigated through intelligent signal conditioning algorithms, however, taking a holistic approach and tackling all parts of the signal chain will ensure a world class experience for customers.

Some of the issues that may be faced in relation to the electrodes are:

1. Electrode Skin Interface
The skin is the largest organ in the body, and is made up of a number of components. The outer layer of skin, the epidermis, has a relatively high impedance that opposes the transfer of the electrical EKG signal. In a wet electrode, this is typically mitigated by the conductive electrolyte; in dry electrodes, sweat performs this function. The electrode converts this ionic charge in sweat into electronic charge that the device hardware can use.

The electrode material also has an impact. Intuitively we may think of conductance being the only important material, but some of our common conductive materials, like aluminium, are terrible ECG dry electrode materials. Understanding the core mechanisms and having the support to analyse and choose the right material for your product can be the difference between success and failure.

2. Dry Electrode Mechanical Design
Unlike traditional medical systems, consumer devices aesthetics are incredibly important for the brand. Smartwatches are as much a fashion item as they are a health monitoring tool and finding this balance between form and function can be a challenge.

The performance of EKG dry electrodes can be impacted by size, position, and surface finish. For a given material, different sizes and the position on the body can affect the interaction with the skin and the resultant signal can vary significantly in quality. The surface finish can alter the contact mechanisms, and some coatings can even further impede the flow of the EKG signal.

B-Secur: Experts in EKG
A rich amount of data can be gathered using wearable sensors in order to monitor and record real-time information about patients’ health. Therefore, it is crucial to manage and overcome these issues to allow improved sensor performance.

B-Secur has over 70 combined years experience in the engineering team, enabling us to provide an end to end system solution for EKG. We have nurtured close partnerships with leading EKG AFE suppliers, allowing our experts to advise on a range of areas to ensure the best possible system performance, including; AFE selection, configuration and setup, optimisation of AFE to electrodes and AFE hardware verification.