Ruike Renee Zhao has faith in the robots.

She has faith in the possibilities they offer and the future they promise.

She has faith in their engineering and their mechanics.

And she has faith in their healing potential.

Zhao’s confidence is hardly surprising, considering she leads a Stanford University research team that is studying the ways in which smart materials can benefit human health. Specifically, Zhao is exploring the feasibility of using such materials to build tiny, flexible robots that could one day wiggle over stomach walls and slink into narrow arteries to treat (or perhaps cure) major health conditions. Some of the team’s research has already produced robots that could remove blood clots within veins, and a hydrogel that pinpointed the cause of neurological disorders by mimicking brain tissue.

“It’s a very different mindset when we think about developing a new technology and then applying this technology to a specific biomedical application,” Zhao, Ph.D., told Stanford Engineering’s news service last spring. “…we need to know what will be important clinical challenges and how our technology could be helpful.”

Zhao and her team find the answers to those questions through a reverse discovery process where they create new “smart” materials first, then consult with physicians to determine applications. As director of Stanford’s Soft Intelligent Materials Laboratory, Zhao has fostered collaborations with researchers in the Department of Medicine and medical experts to visualize devices with greater functionality. The approach has had a snowball effect on innovation, with the number of applications growing proportionately to the number of smart materials created.

“Now we have a lot of novel materials that could be used in biomedical systems,” Zhao stated. “It just opened up so many possibilities.”

Among the possibilities is a magnetic robot arm inspired by octopus tentacles. The arm is comprised of multiple tiny segments, each containing two hexagonal soft silicon plates embedded with magnetic particles interpose tilted plastic panels designed in a kresling origami pattern. The panels’ shape provides the arm with the flexibility to extend into a tube or shrink into an accordion-like configuration.

The arm’s magnetized plates allow for remote control operation within a strong magnetic field (like the kind found in MRI scanners). Zhao’s team tested this feature by surrounding the arm with electromagnetic coils and adjusting the magnetic field’s direction, thus creating the necessary torque to move the individual origami units. The design also allowed Zhao’s team to independently control each arm segment and fine-tune its movements.

“What we’re doing here is mimicking a highly intelligent arm system,” Zhao told Popular Science. “Because its arm is so versatile it could have hundreds, thousands of different motions to interact with objects.”
Those motions, however, are most likely to be more nimble than powerful, as the octo-arm is designed for agility and accuracy rather than strength.

“In the biomedical field, the key is not to lift very heavy weights, the most important point is to accurately control the manipulation of objects,” Zhao noted in the online article. “In human bodies, we don’t have an iron ball inside, we don’t need to deal with very heavy things. What we need is a clever way to navigate through different passages.”

Zhao also came up with another clever way to navigate physiological passages during her tenure as assistant professor at Ohio State University’s Department of Mechanical and Aerospace Engineering. She was part of a team there that developed a new material—magnetic shape memory polymer—that uses magnetic fields to transform itself into various shapes.

The three-ingredient material contains two types of magnetic particles, one for inductive heat and one with strong magnetic attraction, and shape memory polymers to help lock various shape changes into place. Zhao and other researchers made the material by distributing neodymium iron boron and iron oxide particles into a shape memory polymer mixture, according to a Science Daily article. Once all the particles were incorporated, the mixture was molded into various objects, one of which was a gripper claw.

The research team applied a high-frequency, oscillating magnetic field to the gripper claw, which caused the iron oxide particles to heat up via induction and warm the entire object. That rise in temperature, consequently, caused the shape memory polymer matrix to soften; at that point, a second magnetic field was applied to the gripper, enabling it to open and close its claws. When the shape memory polymer cooled, the claws remained locked in position.

The entire process took just a few seconds and produced a material at its locked state that allowed the gripper to lift objects up to 1,000 times its own weight, the Science Daily report noted.

“[This] is a beautiful example of interdisciplinary research,” Dan Finotello, a program director in the National Science Foundation’s Mathematical and Physical Sciences Directorate, said. “This polymer integrates fast reversible and reprogrammable actuation, shape locking, and untethered operation for applications in soft robotics, morphing structures, and deformable electronics, especially for designing active and adaptive guidewires, catheters, and stents that could potentially enable the next generation of biomedical devices for minimally invasive operations.”

Developing the next generation of biomedical devices is contingent on selecting the right materials. Ensuring a product will perform as intended demands an understanding of a medtech materials’ physiological compatibility, physical properties, manufacturing constraints, sourcing, and supply chain logistics.

To better understand the market forces driving the global medtech materials industry and its evolution over the last several decades, Medical Product Outsourcing solicited input from various industry experts, including:

• Thomas Guéguen, general manager at Forécreau America Inc., a family-owned French firm that designs, manufactures, and markets hollow round steel and titanium bars. The metals are used to make coolant-fed cutting tools, surgical tools, and implants.
• Joan Maldonado, Life Science District sales manager at Omniseal Solutions, a Saint Gobain Seals division specializing in high-performance polymer seals.
• Jim Maloney, Development Engineering manager at St. Paul, Minn.-based medical device contract manufacturer Innovize.
• Zachary Murnane, medical fiber global business manager at Honeywell Spectra, a division of industry-specific solutions provider Honeywell.
• Larry Thatcher, president and CEO of TESco Associates Inc., a Tyngsborough, Mass.-based firm offering contract R&D services and contract manufacturing of bioabsorbable devices.
• Onno Visser, managing director at CaP Biomaterials, an East Troy, Wis.-headquartered calcium phosphate biomaterials supplier.

Michael Barbella: What trends are driving medtech material innovation? Have these trends/market forces changed in the last several years (or with the pandemic)? 

Thomas Guéguen: For our applications, we notice that minimally invasive surgery (MIS) and robotics keep having an impact on the design of instruments and raw material choice. Tolerances are getting tighter for MIS and even worse for robotics. Those far-reaching surgical procedures require systems that guarantee torque resistance.

Joan Maldonado: Miniaturization: There is a growing demand for smaller, more compact medical technologies, such as minimally invasive medical instruments and implants. This has driven the need for materials with enhanced features such as strength, flexibility, and biocompatibility. Most miniaturization options are micro-molded and injection molded, which restricts some material options. So, many companies including Omniseal Solutions, work on modifications to machining processes to create smaller product options with machined materials.

Sterilization: The need for effective sterilization and disinfection solutions has increased with the pandemic, driving the development of new materials for sterilization and disinfection technologies.

Surgical robotics is driving the development of materials that are lightweight, flexible, and durable. Materials such as polymers and composites are being used to create robotic arms and instruments that are strong yet lightweight. Furthermore, medical devices that utilize surgical robotics require materials that are biocompatible, non-toxic, and able to withstand body fluids and sweat.

Jim Maloney: The trend towards wearable sensors, micro fluidics and long-wear wound care products have driven the market to produce adhesives that will hold up for long-term wear and hold the tack level so the device will not release from the skin. Conductive inks can be printed in intricate patterns. Some new hydrogels are conductive, as well as other adhesives with longer wear characteristics. The new wave of hydrogels have varying amounts of tack level, something we haven’t seen in past hydrogels.

There’s an increase in double-coated adhesives that have a variety of adhesives that are coated on either side of the carrier to enable the production of multi-layer stacked constructions, with features in each layer.

Zachary Murnane: Innovation in the medical device industry is largely being driven by the desire to make devices and implants smaller. This trend is exemplified by the move to minimally invasive surgical techniques such as laparoscopic and robotic surgery. Honeywell is committed to building a collection of medical grade fibers that support this. At the beginning of 2023, we introduced Spectra Ultra Fine BIO fiber in 25 decitex (dtex), the newest addition to our Spectra Medical Grade (MG) BIO fiber portfolio. The fiber enables minimally invasive cardiovascular and orthopedic device design and helps increase device longevity, given it is a stronger fiber compared to polyester, nylon or other technologies used. In fact, Honeywell’s portfolio of Spectra MG BIO fibers are 15 times stronger than steel by weight and three times stronger than polyester by volume. Spectra MG BIO fiber is biocompatible, reducing the risk of body inflammation and irritation. Spectra MG BIO fiber has also received ISO 13485 certification for manufacturing, adhering to the highest quality management standard in the medical device industry, such as providing customers with end-to-end manufacturing lot traceability. A wide range of manufacturers can now utilize this ultra-fine denier fiber for increasingly smaller, stronger, and lighter devices. Access to this technology is critical to enabling continued innovation that makes cardiovascular and orthopedic procedures safer and more successful for patients worldwide.

Larry Thatcher: As a company that deals almost exclusively in bioabsorbable medical devices, TESco has seen a steady desire from clients for “next-generation” materials that can replace metal implants. Clients want to be able to switch surgeons over to bioabsorbable materials by offering a next-generation material that provides comparable clinical utility without any changes in operative technique. If you can take a power driver and drive a metal ACL screw into bone, then the next-generation bioabsorbable material must be able to do the same thing. While this seems simple enough, as there are current material formulations available that can achieve this goal with excellent clinical results, the twist comes in that clients want a material that is “new” and provides “market differentiation.” This drives the question, how do you define clinically relevant and efficacious results with good science, not just the same material with something new added in that might present marketing appeal, but does not provide a significantly relevant clinical benefit.
Further complicating this quest for a next-generation material is both process development and the regulatory pathway. A new material may involve both new tooling as well as significant processing changes that affect direct costs and regulatory submissions. We are also seeing a trend where device designers who have been working with metal or bio-durable polymers like PEEK are unaccustomed to designing with materials bespoke to a specific indication and solicited healing response. Sometimes they are looking for a one-size-(one material)-fits-all approach, which may not be readily possible with a more complex next generation bioabsorbable material.

Onno Visser: There is a trend towards patented variations that seem to be increasing as companies try to provide higher performance materials than the now standard commodity products based on just hydroxyapatite (HA) and tricalcium phosphate (TCP). Modifications include special particle morphologies and/or specific trace metal contents. CaP, being a contract manufacturer, is making some of these new products for the patent owners. To ensure a satisfactory relationship, CaP works with these customers to develop scaled up production processes that are as efficient as possible while maintaining quality standards.
This helps to provide a favorable cost structure and sustainable long-term production contracts. A significant development has been the shift from using bone void granules (as-is) to including them in injectable and/or moldable formulations such as putties. Based on feedback from its customers, CaP has provided materials that work optimally in such formulations.

Barbella: How have adhesive materials evolved with the significant growth in medical wearables in recent years?

Maldonado: Adhesive materials have evolved significantly in recent years with the growth of medical wearables. Adhesives that can provide strong, reliable bonds with medical wearables have become more important as medical wearables become more sophisticated. Adhesive materials must be biocompatible, non-irritating, non-toxic, and able to withstand body fluids and sweat. In addition, medical wearables often require adhesives that are strong and flexible, yet still able to be easily removed.

Maloney: With the wearable sensor market, adhesives have to stay on longer and have greater tach to the skin so the device will stay in place. In addition, we are seeing an increase in silicone-based adhesives, which are skin friendly, but require some expertise to properly process via rotary die cutting. The evolution of longer-wear adhesives and double-coated adhesives with skin-friendly adhesive on one side of the patch and acrylic adhesives on the other side to attach a device or electrics that is integrated onto the patch. The urethanes with casting sheets help with converting, as it keeps the material from stretching so it can be laminated to another substrate without stretching. Conformable urethanes create a “pocket” that a device, foam, or gauze can wrap around to keep the dressing smaller in size.

Barbella: How have medical materials evolved over the last two decades? What new substances have been introduced and what has been their impact on innovation?

Maldonado: Over the last two decades, medical materials have evolved significantly. New materials such as polymers and composites have been introduced and have had a major impact on innovation. Polymers and composites are lightweight, durable, and biocompatible, making them ideal for use in medical devices. In addition, advanced materials such as metallic alloys, ceramics, and bioresorbable materials have been developed to meet the demands of medical applications.

Thatcher: Over the past two decades we have seen many material innovations, from resorbable magnesium materials, to bioglasses. While these innovative materials provide benefits to niche areas, no one material innovation over the past two decades has been able to impact the bioabsorbable orthopedic material field as has the processing of materials compounded with biphasic or bTCP ceramics. In the past two decades we have seen the steady decline in the use of neat (base polymers), such as PLA, to almost exclusively a type of compounded material. This is due in part to the fact that compounded materials provide better healing and mechanical properties. It has been critical to learn and understand the clinical outcome and metabolic fate with any of the “new” materials, just as we have grown our understanding of the in vivo degradation and metabolic fate of absorbable materials we have been using clinically for decades.

Barbella: How have materials suppliers managed the supply chain challenges prompted by the pandemic, and strategies are they planning to use to minimize such risks going forward? Are material shortages to be expected this year?

Guéguen: The speed to launch new products in the orthopedic industry has been and continues to be critically important. With the increasing time required in early product development and regulatory stages, shortening manufacturing time is one of the few areas of opportunity remaining for reducing the time to launch new products. Recently, the focus has been to deal with the impact of the pandemic—supply chain disruption and personnel shortages. Manufacturers are looking for supply chain reliability—raw material stock and simplified manufacturing steps with as little intervention from outside vendors as possible.

Maldonado: Material suppliers have had to manage the supply chain challenges prompted by the pandemic. To minimize such risks going forward, suppliers have had to adopt strategies such as diversifying their supply chains, increasing their inventory levels, and utilizing digital platforms and technologies to manage their supply chains. Despite these measures, material shortages are still likely to occur as demand continues to outstrip supply. Additionally, the pandemic has caused disruptions in the global supply chain, which could further contribute to material shortages.

Thatcher: Generally, we have seen an increase in lead times and cost for bioresorbable materials. Many suppliers now require several months additional forecasting. This in turn has required CDMOs like ourselves to increase our safety stocks as the materials suppliers deal with basic raw material shortages. Based on our experience and discussions with material suppliers we do not anticipate any significant material shortages. Part of our business strategy of risk mitigation for sourcing raw materials had already included qualifying two sources for all raw materials, as well as using U.S.-based sources when they are available.

Visser: For some products CaP has special raw material requirements, often with only one qualified supplier. When such a raw material has become unavailable, CaP has resorted to either chemically synthesizing the raw material from available chemicals capable of imparting the correct properties to the synthesized material, or modifying available, alternative sources of the raw materials through physical and/or chemical processes to make them suitable for use. Once CaP has developed processes to produce the alternative raw materials, the production processes utilizing them have gone through revalidation in cooperation with the affected customer(s). By completing these actions in a timely manner, delivery delays of the affected finished products have been minimized.

Barbella: Can you share an example of an innovative material solution your company developed to meet a challenging customer request?

Guéguen: We are working with a large OEM on a titanium ultrasonic dissector to cut tissue. A cooling liquid enters through one and exits through the other. Forécreu’s ability to manufacture two lumen extruded bars in Ultrasonic compatible Titanium has shown to become a major advantage to machine long instrument parts.

Maldonado: We provided engineering support and expertise for multiple material selections and medical grade options for a surgical hand piece with 12 individual parts. Materials included PEEK, polycarbonate, polybutylene terephthalate, and polyoxymethylene. Each part was designed to meet a tight tolerance, manufacturing repeatability and quality standard. Prototyping quick turnaround was required and the ability to design product, tooling, and production in-house made the quick turnaround timing successful. So, the product needed several different medical grade materials and each required a unique material to match operating conditions. Also, adhesion options were unique for each material used. In this instance, multiple materials were used for successful operation.

Maloney: As a medical contract manufacturer, producing film-based constructions for our customers, we product to the exacting standards of the OEM. Getting involved early in the design process enables us to guide our customer toward the most efficient and reproducible process, to transform the materials into a functional component or device.  We are able to influence material choices, and recommend process aids.

With the advent of a wider range of low tack adhesives, it helps us to develop challenging processes which we could not do in the past. One process had numerous material inputs and needed to remove waste from die-cut parts, but the adhesive would not release from a tight release liner. We tried our standard low-tack adhesive to pull the slug out but it was not aggressive enough to pull it from the liner. Then we went to an aggressive adhesive and it removed the slug, however, it stuck to the bottom side of the part. The solution was in a new low-tack adhesive that had the properties we needed. We were able to perform multiple die cuts in multiple layers of materials, pulling waste out and keeping the wanted part on the web.

Murnane: The Honeywell Spectra Medical Fiber team recently worked with one of our customers to help increase the final pressurization performance of their end medical device by 50%, supporting a new product line for medical therapeutic applications. We were able to achieve this for our customer by implementing innovative methods for processing our Spectra Ultra Fine BIO fiberin 25 decitex. We also collaborated with our end customer’s design team to develop a revised textile using the fiber. In addition to achieving an increased level of performance for our customer, this effort also resulted in a more efficient manufacturing process for them, helping to reduce the overall product cost by minimizing the fiber scrap rate in the customer’s textile conversion process.

Visser: Examples that represent our core competence that we’ve recently completed have been scaling up the manufacturing of a high-surface area bi-phasic bone void filer granule. The original material had been developed in a lab and was manufactured in batches of several grams. We’ve successfully upscaled to a process that is able to deliver the volumes (100-200kg/year) our customers envision. Another process was to duplicate a material that another supplier was manufacturing for a customer, to de-risk their supply chain. This is something we’ve recently seen more often, in reaction to the recent supply chain disruptions.