Exploring Miniaturization in Bioelectronic Medical Devices

Introduction 

In 1958 an external pacemaker was introduced, 65 years later the leadless pacemakers are on the market. Over that period the volume of the pacemaker was reduced by 99.8%, the weight was reduced by 99.3%, all while adding additional functionality such as rate responsive pacing, wireless programmability, increased battery longevity, adding sensors, and MRI compatibility. 

What is Miniaturization?

Miniaturization refers to the process of designing and manufacturing smaller versions of devices, components, or systems while maintaining or enhancing their functionality and performance. This trend is prominent in various industries, including electronics, medical devices, and bioelectronics, where advancements in materials, precision engineering, and technology enable the development of compact, lightweight, and efficient products. In the medical device industry, for example, miniaturization allows for the creation of smaller, less invasive devices, such as implantable sensors or bioelectronic devices, which improve patient comfort and reduce recovery times.

Why is Miniaturization Important?

One of the most important benefits of this incredible miniaturization of biomedical devices is significantly less invasive surgery for patients. In 1958, implanting pacemaker leads, or a pacemaker required open heart surgery which required cutting through the breastbone and spreading the ribs to reach the heart and carried a significant risk of complications and lengthy recovery periods. Today, leadless pacemakers can be placed via catheter through the femoral vein with reduced risk of complications, and significantly faster recovery periods.  

Longer battery life is critical for patients. Leadless pacemakers have a median longevity of 16.7 years, which allows a single pacemaker to last for the lifetime of most patients, rather than having to undergo a pacemaker replacement surgery. In contrast, the early pacemakers lasted only hours when operating off batteries. 

With miniaturization comes the possibility of adding in additional features such as rate adaptive pacing, which adjusts the pacing rated based on the activity level of the patient, increasing cardiac output during exercise. This feature is enabled by miniaturized sensors such as accelerometers, intrathoracic impedance measurement, and heart rhythm analysis. Other features such as wireless programmability, MRI compatibility, and heart rhythm data collection/analysis are also enabled by the ability to cram more functionality into a smaller form factor. 

What technologies enable miniaturization?

Transistor Density 

The primary driver of this miniaturization goes hand in hand with the significant advances in electronics and electronics packaging across all industries. The best-known example of this is “Moore’s Law” coined by Gordon Moore of Intel, which postulates that the number of transistors doubles roughly every two years. In the early 1970’s state-of-the-art semiconductor processing technology would allow transistor densities of up to 200 transistors per mm², while transistor densities exceeding 100 million transistors per mm² are possible with current semiconductor processing technology. This continual reduction in transistor size also benefits battery life, with less energy required to change the state for each transistor. 

IC packaging 

Along with the reduction in transistor size have come advances in IC (Integrated Circuit) packaging such as: