Systems that deliver medication — whether implanted or at the patient bedside in the hospital — are often vital for the survival of patients. Drug-delivery devices include ambulatory infusion pumps, patch pumps for insulin delivery, linear peristaltic pumps, rotary peristaltic pumps, and tiny implantable pumps for those with chronic pain. These systems require absolute reliability, which ultimately minimizes risk and lowers costs for both hospitals and users. Designing this high level of reliability into these systems requires the latest advances in motor technology.

Market Drivers

Flex rigid solutions can save space in drug pumps. (Credit: Maxon Precision Motors)

Growth in the telehealth and mobile health market is just one change that is influencing the requirements for drug-delivery systems, driving everything from ease of use to automation. In addition to telehealth enabling remote diagnosis and treatment, mobile apps now do everything from reminding people when to take their pills, to providing a device to deposit those pills, to collecting specific data about a person’s body to sound an alarm when a problem occurs.

With these changes in the marketplace, many pharmaceutical companies are focusing on creating liquid medications to make delivery simpler, adjustable, fully automatic — and easily personalized. While the adoption of protein- and gene-based therapies, for example, has been limited by the need for better methods of delivery directly into cells within tissues, liquid options will open doors for micro-molecular delivery of proteins, hormonal injections, and even specialized genetic therapies.

Liquid dosing is not new, but now more than ever, delivery systems must be accurate, repeatable, long lasting, and quiet. These systems must enable medicines to be delivered locally, eliminating the need for patients to take oral medications that might hinder their ability to perform routine functions such as driving. Localized, automated delivery also decreases the overall amount of medication that must go into a person’s body, which reduces unnecessary side effects. Plus, for serious patient care, the ability to deliver medication locally eliminates the possibility of someone becoming addicted to a drug.

Requirements for portable drug-delivery systems include user comfort, which dictates that a device be super compact to fit seamlessly into a daily routine. Portable systems must produce very low noise and offer extremely long battery life. These devices must be flexible enough to fit into all aspects of a person’s life, which means being water and chemical resistant and mechanically and electronically robust.

Micro Drives for Drug Delivery

Micro drive systems for medical applications are not only compact but are designed for low noise and to provide high efficiency. (Credit: Maxon Precision Motors)

Finding the perfect drive solution for each type of drug-delivery system requires expertise in balancing critical requirements like reliability with the need for a small footprint. For example, Maxon Precision Motors helped one customer design an artificial pancreas drive system with a dual pump that measures the blood sugar and delivers insulin and glucagon to balance those blood sugar levels. The benefits of this drug-delivery system include its ability to control blood sugar levels more precisely than the patient’s original pancreas.

Another example is an implantable pump that can deliver the prescribed amount of a drug directly to the area it is needed rather than throughout the body. In this way, the concentration of the drug can get higher, while the portions can be reduced. In this case, one of the challenges was to make the implantable pump as small as possible so that the patient wouldn’t become uncomfortable. Because lower volumes of the drug can be used, smaller components can be used, which translates into convenience for the patient. The final size of the battery-powered pump is only 12 mm (outer diameter), and it uses only 0.2 W of power.

Thanks to developments in the mobile phone industry, higher-power-density batteries are now very small. Maxon’s EC 4 or EC 9 flat motors, for example, are ultracompact, highly efficient micro drives. The EC 4 is only 4 mm in diameter and comes in two different lengths, with power ratings of 0.5 and 1 W. Certified in accordance with ISO 13485, the brushless micro drive is ideal for medical applications. Equipped with an ironless winding, the EC 4 works well in drug-delivery applications because of its robust design, high power density, and energy efficiency. Combined with the GP 4 planetary gearhead, the precise and reliable EC 4 becomes a compact drive ideal for use in micropumps. Adding the company’s patented double lead screws increases drive efficiency.

All mechanical and electrical interfaces affect the size of the final device. Components can quickly limit possibilities. Reducing the dimensions requires reducing the number of interfaces and combining functions wherever applicable. Reducing overall size was a key driver behind Maxon’s complete subsystems. In drug pumps of any kind, the company uses flex rigid printed circuit boards to save space. In most pump devices, additional sensors are used such as force sensors to detect occlusions and position sensors to provide redundancy, both of which are deeply integrated into the subsystem.

A 4-mm micro motor and gearhead for medical applications.

For more invasive, implantable pumps, Maxon has designed and manufactured a drive using biocompatible materials in the manufacturing process. The outer parts of the pump are completely titanium, which requires a high level of expertise to machine and laser weld. The entire assembly of the implantable micro drive takes place under cleanroom conditions to ensure that when the pump is implanted, the drive inside will not lead to any type of allergic reaction or rejection.

Some of Maxon’s smallest micro drives for medication delivery systems are based on nonturning technology where linear movements to the pump are based on a solenoid concept and are operated via a voice coil motor at a particular frequency. These devices are extremely compact and are designed to provide efficiency while maintaining a user-friendly interface to all types of control systems. Long life is an important factor in final designs because there must never be any concern over the ability for the pumping systems to operate accurately and repeatedly, especially when considering life or death situations such as drug delivery. Control of the pump must also be highly efficient and reliable. Maxon’s motors for the drive train — such as position-controlled or speed-controlled subsystems — use standardized driver electronics, which means that standard software or modified firmware can be used. Specific customer needs, though, depend on the company that designs the procedures for the human interface, in which case they provide their own software so that it is easily understood by the user.

Advances in motor technology are helping lead to breakthroughs in drug-delivery systems from ambulatory infusion pumps the tiny implantable pumps for chronic pain. Special teams at Maxon are working on the next generation of drive solutions for drug delivery as well as for permanent and disposable devices for syringe and needle-free applications to ensure that reliability is designed into each system.

This article was written by Carsten Horn, Business Development Engineer for Maxon Precision Motors, Fall River, MA. For more information, Click Here.