Streamlining Medical Wearable Device Design for Performance & Total Cost Optimization – Part 2

We sat down with one of our Field Application Engineers to discuss how to optimize and streamline Medical Wearable Device design. Boyd is an expert in streamlining innovative design, manufacturing, and assembly of medical wearables to help product designers and medical device companies design for excellence (DFx). We help designers consider patient comfort & safety, manufacturing efficiency, product lifecycle, and total cost while navigating complex regulatory processes, providing global agility, assuring business continuity, and accelerating time to market.

Here are common questions we get as we work through Medical Wearable Device design projects with leading medical device design and manufacturing clients:

How do you incorporate electronics and functionality into extremely thin medical wearable devices?

Medical Wearable Device designers are tasked with packing a lot of sensitive and critically important electronics into very thin, streamlined wearables. There are all different types of sensor technology used because as sensors get smaller and less expensive, they’re being integrated into more devices and enabling new medical technology.

Types of Sensors Used in Wearable Devices

Electrocardiogram (ECG) monitoring devices, as an example, sense electrical stimulations based on the location of conductive electrodes worn on the chest. These patches are used to sense things like heart rate, respiratory rate, and arrhythmias. Product designers are also learning how to adapt acoustic sensors to collect heart metrics in different locations like the wrist.

Medical Wearable Devices also sense skin or body temperature with thermistors or thermocouples. Optical sensors on a wearable can measure oxygen saturation. Accelerometers and Gyroscopes can measure the wearer’s activity, movement, and positioning and can measure things like posture and fall detection.

Sharing Medical Wearable Device Data

Each sensor collects data that connects to either an embedded circuit board sandwiched within the wearable patch, or through electrical snap connectors to an external, reusable electronic module affixed to the wearable. Most of these wearable devices are using a Wi-Fi or Bluetooth transmitter to broadcast data to a secure cloud storage source accessed remotely by patients and doctors. Sensors and electronics must also be powered by a small battery which must be considered in the assembly process.

Assembling Medical Wearable Device Components Together

Medical Wearable Devices feature a large amount of very small, precise components. Due to their slim designs, there isn’t much room to accommodate all these components and there is certainly no room for misalignment. Meaning design for manufacturing and assembly accuracy are exceptionally important. Boyd has a lot of complex rotary converting processes that we leverage to cut and assemble with tight tolerance control and registration accuracy in highly automated processes. However, many medical wearable designs cannot be fully converted “on-press” in one continuous process utilizing the efficiency of traditional reel-to-reel converting methods. Because of complexity of the components used like the insertion of an electrical assembly or the attachment of snap connectors or the addition of a molded plastic housing, separate assembly steps are often required. This presents special assembly challenges that require creative process flow and innovative assembly fixture design to achieve efficient throughput and reduced labor costs.

Balancing Volume and Assembly Cost for Medical Wearable Devices

Newer medical wearable designers face special challenges as start-up companies who are trying to introduce a new technology into the market, facing long product development cycles due to regulatory / compliance requirements, and a slow ramp up due to long time of adoption. This means the economics for a fully automated assembly process are typically not feasible given the high NRE investment. Often it comes down to an efficient manual or semi-automated assembly process to help minimize these non-recurring expenses to give your wearable the best chance to succeed in the market. This is where Boyd excels in determining how best to assemble a complicated design in an efficient manner, leveraging the best of our diverse processes to assure trusted quality control. Blending the best of high precision converting with innovative assembly techniques under a highly documented, and process-controlled quality system.

Streamlining Medical Wearable Device Design for Performance & Total Cost Optimization – Part 1

We sat down with one of our Field Application Engineers to discuss how to optimize and streamline Medical Wearable Device design. Boyd is an expert in streamlining innovative design, manufacturing, and assembly of medical wearables to help product designers and medical device companies design for excellence (DFx). We help designers consider patient comfort & safety, manufacturing efficiency, product lifecycle, and total cost while navigating complex regulatory processes, providing global agility, assuring business continuity, and accelerating time to market.

Here are common questions we get as we work through Medical Wearable Device design projects with leading medical device design and manufacturing clients:

What are the best and safest ways to attach Medical Wearable Devices to the skin?

There are two important factors to consider regarding the attachment of the medical wearable: The attachment of the device itself to the skin and the style of conductive electrode used. All devices that attach to the skin must be highly tested and regulated to assure patient comfort and safety. Wearable devices must reliably attach to the patient for intended wear times without irritation while still being removable without damaging patient skin.

Wearable Device Adhesive Considerations

Selecting the right medical grade adhesive for wearable devices are selected based on:

• Required adhesion level (for example higher adhesion is necessary for longer wear times),
• Breathability: water against the skin needs to escape to help promote better wear time
• Ease of Removability,
• Wearer Comfort Level,
• Repositionability or Re-application (if required), and
• other application considerations.

Medical Wearable Design and Use Conditions

The shape and type of the skin contact layer may also be influenced by whether the wearable device needs to protect hydrogel electrodes or sensitive electrical components sandwiched within the patch from outside water ingress. In some unique applications when wear time is short, water ingress is not a factor, and repositionability of the wearable is desired, the adhesive skin contact layer can be foregone and rely on hydrogel components to provide the desired level of adhesion. We collaborate with many global raw material suppliers that are the world’s leading innovators in skin contact comfort and performance to help recommend materials to customers based on these factors to improve product comfort, care, and safety.

Medical Wearable Device Electrode Components

As for the electrode component, one traditional type of material used is open cell, medical grade foam pad saturated with a conductive gel as the electrically conducting medium. This style electrode can be more difficult to handle as a raw material and can impact manufacturing efficiency and cost. We have been steering customers towards hydrogel-based electrodes. Hydrogels present some cutting challenges, but our proprietary converting methods can offer a better option: they’re available in roll form and solid means a component easier to cut, handle, and place with greater quality control. There are several different global hydrogel raw material manufacturers available that offer responsive support and supply chain stability, enabling us to secure dual sources that can be compliant with regulatory and certification controls. Many material formulations to choose from, means we can typically find the right hydrogel to fit the specific electrical and application requirements.

We’ll continue our interview with our Medical Wearable Device FAE in an upcoming post!

Smart wearables are becoming ubiquitous and witnessing revolutionary developments each day, fueling a multi-billion-dollar industry. From medical wearable devices to collect diagnostic data, smart tattoos that track sunlight exposure, to smart insoles that monitor your footsteps, technological advancements are pushing the boundaries of wearable innovation. As the wearable industry is still relatively young, functional printing professionals including technical printers, designers, engineers, and system integrators are constantly working together to investigate new processes, materials, technologies, and testing methods. Aside from the dominant world of smart watches, there has been significant growth and interest in smart medical wearables, clothing, electronics, and sensor solutions. But what are some of the common considerations when developing a new smart wearable?

Biocompatibility:

Since most wearables come in direct or close contact with skin, biocompatibility is of paramount importance to ensure user safety. Depending on the intended use of the device, compounds in wearable substrates and construction layers can potentially be exposed to sweat, rain, humidity, sunscreens, and insect repellants. A comprehensive understanding of the interaction of various external factors is crucial towards eliminating unwanted risks such as skin sensitization, allergic reactions, and irritation. While there are no industry standards governing biocompatibility across all wearable devices, ISO 10993 provides a framework for wearable medical devices.

Power Management:

Effective power management still remains a significant hurdle in developing wearable solutions. Thin and compact batteries often translate to shorter battery life and companies are continuously struggling to extend the battery life for devices to last at least one cycle of usage. While space is a huge constraint when working with small and lightweight devices, companies are harvesting energy by employing solar cells or powering batteries using the body movement and body heat of the wearer. Companies are actively trading Wi-Fi connectivity with Bluetooth communication modules for efficient power consumption and pivoting towards wireless power supplies through inductors. For most wearable garments intended for long-term use, the batteries must be easily replaceable or rechargeable.

Flexibility and Stretchability:

Smart wearables, especially garments, are susceptible to a great deal of stretching. Flexibility, the basic form factor of wearables, has made flexible printed electronics be actively pursued as an alternative to costly silver threads and yarns sewn into apparels. Depending on the final application, wearable substrates need to strike the right balance between flexibility, stretchability, and stability. In addition to experimenting with new substrates, the industry is currently leveraging medical-grade materials including polyether-based thermoplastic polyurethane (TPU), polyester-based TPU, polyethylene terephthalate (PET), and fabrics such as spandex, nylon, elastane, and cotton. Functional inks are often printed on flexible substrates and as the user wears or moves with the garment, there is a certain amount of stretch that occurs. Therefore, inks need to exhibit acceptable change in resistance with repeatable stretch and recovery cycles.

Sealing:

Conductive epoxies, typically used to apply components on to circuits, are often not a feasible solution when dealing with wearable applications as they tend to break under stress. Due to this, applying additional components such as surface-mount LEDs and active PCBs can be challenging. The ability to incorporate electronic components smoothly into apparel whilst ensuring strong adhesion during bending, creasing, and flexing is key to the success of smart wearables. In addition, smart and medical wearables intended for long-term use must be safe to submerge under water without damaging the circuitry, and physically endure multiple wash cycles. Achieving a water-tight seal and protecting the power source from environmental factors is vital for ensuring optimal performance and durability of the device. For electronic equipment, Ingress Protection (IP) rating specifies the degree of protection from solids and liquids including dust and water. Whether it is fusing stretchable materials with thermoplastic-adhesives backing or applying hot-melt adhesives to polyester circuits, thermal bonding is one of the most common sealing approaches in wearable solutions. Pressure sensitive adhesive (PSA) lamination is another approach that requires a medical-grade adhesive to apply a patch directly to the skin of the user. TPU overlaminates, printable insulators, and PET overlaminates are often used for sealing and potting. The wearable technology industry is migrating towards a “smart system”, a world where all devices from head to toe communicate with each other to create a single ecosystem. As existing technologies and processes evolve, new norms, standards, and specifications for the industry will gradually develop. With a promising future in sight, the widespread adoption and integration of smart wearables in our daily lives will continue to grow. Boyd has years of experience creating custom smart wearable solutions. To learn more or discuss your project needs, schedule a consultation