Perspectives on Miniaturization
In the effort to make medical devices smaller, what has been the most challenging obstacle you have faced and how were you able to resolve this problem?
Vice President and General manager, Tadiran Batteries
Reducing the size of any battery-powered medical device starts by increasing energy density, which allows the device to be smaller and more feature-rich without compromising power. Alkaline and rechargeable batteries typically lack the desired energy density and shelf-life, and cannot tolerate high temperature autoclave sterilization procedures. To address this challenge, Tadiran developed TLM Series lithium metal oxide batteries, which consist of a carbon-based anode, a multi metal oxide cathode, and an organic electrolyte. AA-size TLM-HE cells will offer a discharge capacity of up to 1,100 mAh, with an open circuit voltage of 4 V, capable of handling 5 A continuous current and 15 A pulses. TLM batteries offer exceptionally long storage life, a wide temperature range (-40 to 85°C), and a unique voltage curve that allows devices to be programmed to provide low battery status alerts. TLM cells are also extremely safe, with non-toxic, non-pressurized solvents and anode materials that are less reactive than other lithium cells, conforming to UN 1642 and IEC 60086 standards, and can be shipped as non-hazardous goods. Typical applications include surgical drills and power tools, and patient-worn devices that track movement, monitor vital signs, or deliver medications.
Gabriel O. Adusei, MSc, PhD
Independent MedTech Consultant, Founder, International Association of MedTech Consultants
The advent and promotion of hand-held devices and mobile technology for monitoring, diagnosing, treating, and managing health conditions have inspired many manufacturers to show increased interest in the miniaturization of medical devices, such as surgical instruments and imaging tools. Minimally invasive medical techniques have encouraged the use of miniaturized devices. One of the integral items that have helped to facilitate the use of miniaturized medical devices has been the metal and plastic tubes through which these devices pass, and that perform vital associated tasks, such as aspiration, the cleanout of debris, and injection of fluids, such as medications. Composed of medical-grade in sizes commonly as thin as a pin, these tubes are used for a wide assortment of miniature medical procedures, ranging from ultra-fine catheters to miniscule implants.
When designing tubing for medical applications, it is vital to optimize the needed diameter and it must have an even, smooth ID. Also, specialized shapes may be essential, requiring swaging, flaring, or threading a portion of a tube, or making a one-piece component to avoid connection failure. In efforts to make medical devices smaller, R&D scientists and engineers do consider many factors such as choice of materials, bulk and surface modification, physical and chemical properties, biocompatibility, and rate of release of active(s) from them if so designed.
Global Healthcare Marketing Director, SABIC Innovative
The biggest challenge we have had to overcome as medical devices get smaller is making sure we have a portfolio that is going to meet this challenge.
For example, three trends in healthcare today are miniaturization, portability, and increasing a medical device's aesthetic appeal. As customers design their devices, they are looking to make the walls thinner for weight out and also to make the part's design more appealing. The devices are still required to meet the same, if not more, demanding performance requirements in terms of practical toughness.
Another area of concern around design is making sure that as parts become more complex, there are materials that can mold easily and fill the tools completely. What we have done over the past few years is introduce materials across our portfolio that can stand up to this challenge and provide customers with thinner wall, better processing materials.
For example, using Cycoloy resin in the new Resmed device enables this company to design a thinner wall chassis that still meets the UL rating needed while still delivering high flow for the complex design. Another example is the GE Ultrasound. Again, another grade of Cycoloy resin that enabled GE to meet the similar requirements as the Resmed device. Lastly, over the past few years and as we look forward, we are continuing to expand our portfolio with materials such as Lexan EXL co-polymers and Lexan HFD co-polymers that enable a balance of high flow and desired mechanical properties, ultimately leading to customers being able to design smaller, more intricate parts without sacrificing durability. In my opinion, this trend will continue as the growth of home healthcare continues and devices become more portable and sleeker in design.
W. John Bilski
Senior Engineer, Thermacore Inc.
Thermacore works with OEMs who build medical devices to create efficient, reliable instruments and testing equipment. If not properly managed, the heat that is generated from the electronics in these devices can ultimately compromise patient safety.
The biggest challenge we have faced was with a customer whose device was not working properly because an integrated circuit (IC) was overheating. The printed wiring board was located in the middle of the case, with other components above and below it.
To overcome this challenge, we designed and built a heat pipe assembly to remove the heat. The assembly included a heat pipe with a plate in the middle and two blocks on either end of the pipe. The heat pipe was partially flattened and bent to meet the required space constraints. The IC input its heat to the plate in the middle of the heat pipe assembly. The heat pipe then maneuvered around components on either side of the IC to reach two spots on the case where it could dissipate the heat.
Heat pipe assemblies, which do not consume any power or contain any moving parts, are an ideal solution for managing heat in medical devices. After our solution was installed, the device immediately began to perform as expected.
Medical Key account Manager, Micro Crystal
One of the key obstacle we face as a crystal supplier (for industrial and medical applications) is the willingness of the IC manufacturers to adapt the design of the oscillator part of the circuits to the parameters of the smaller crystal products. Typically, smaller crystals will inherently have slightly higher ESR values than larger crystals. With state of the art IC design, this can be overcome, however, it is necessary to take this into consideration at the early stage of the IC design. A close cooperation between the IC design house, the crystal manufacturer, and the medical device manufacturer is necessary to ensure optimal operating conditions throughout the defined product specifications.
Director of Product Management, TE Connectivity, Touch Solutions
Driven by attractive and convenient consumer electronics, the trend in medical devices is toward increasingly powerful yet smaller devices, with the added complication of designs that eliminate fan assisted cooling. Air gaps within these devices must be kept to a minimum and much of the heat must therefore be conducted to the interior walls of the enclosure, transferred to air utilizing natural convection or radiated away from the source, in a combination that keeps operating temperatures below design limits. As the density of PCBs increased, problems were inevitable. Resolution has been through a multi-faceted approach that included thermal modeling and verification, testing a variety of designs to address hot spots, and coupling heat generators so that virtually every exterior surface of these devices is performing as a thermal sink. Additional time must be allocated for the (design/modeling/verification/testing at design limits) cycle that will likely require several iterations to achieve a successful product design. New designs incorporate thermal extraction considerations from the outset.
Dr. Jeffrey Purnell
Medical and Pharmaceutical R&D Group Leader, Adhesives Research
Trends influencing in-vitro diagnostic devices, such as increasing test speeds using smaller sample volumes and quantities of biomarkers, are driving designs that use smaller capillary channels than before. As a result, the viscoelastic properties of the adhesives used in device designs with larger sample flows may not be suitable for smaller channel designs. In these instances, a dual-stage UV-curable PSA is a good substitute. This unique construction initially functions like any other PSA for in-line processing with quick-stick properties for bonding and laminating components within an IVD device. Once assembled, the laminated construction is briefly exposed to UV light, which further cross-links the adhesive, making it more cohesive and eliminating the risk of cold flow.
Device manufacturers can increase test speeds with a smaller sample volume by utilizing adhesives with hydrophilic capabilities. Hydrophilic PSA constructions serve a dual purpose in that they bond the components of the diagnostic device together while also creating a high energy surface to enhance flow of the biological fluid. The hydrophilic PSA may also reduce the surface tension of a fluid to allow rapid transfer of the fluid from an inlet area to a remote reagent area located in an IVD device. As a result, the rapid spreading of the fluid can reduce the time needed for analysis and enable the use of a smaller sample volume. Hydrophilic coatings and PSA systems may be used in a variety of in-vitro diagnostic devices, including capillary flow, lateral flow, microfluidic, microtiter plates, and electrophoretic devices.