In a recently published white paper, imec provided an overview of the building blocks for the next generation of medical implants. Integrating the building blocks into smart chips provides a comprehensive solution that is smaller, smarter and more connected.
Medical implants in evolution
Pushed by the technological progress in nanoelectronics, implantable devices are becoming smaller, smarter and more connected. In turn, this results in more efficient devices with better performance and increased patient comfort. It also warrants a whole new vision for how to design and manufacture these types of devices. The next generation of implantables require an integrated approach starting from a specific application. By offering customized integrated circuits that combine state-of-the-art technological skills and knowledge of regulatory pathways, imec addresses the challenge of designing small devices packed with functionality.
Potential applications of implantables.
Small but powerful
Chips are becoming smaller but contain more functionality and sensitivity than ever. This revolution in miniaturization is important for medical implants and opens the door to small, lightweight devices that consume little energy and are comfortable for the patient. This makes them a valuable tool for doctors to offer treatment and provide more customized diagnosis.
Medical implants don’t have to lose functionality just because they are getting smaller. On the contrary, these devices are packed with functions and have become even smarter. Using a closed-loop system, they contain different sensors, actuators and sometimes even the algorithms to enable a link between the two.
The new generation of medical implants puts a strong emphasis on wireless technology, for charging the implant and sending the data it generates, making them more connected. To charge the implantable device, for example, you can connect with a portable device such as a watch or a bandage. The implant could also communicate with a smartphone to display its operating status and possibly request sensor data that is transmitted either from the smartphone or directly via the implant itself to the attending physician.
Custom integrated circuits
To make such medical implants a reality, imec develops specific integrated circuits (ICs). Unlike commercial alternatives, these are unique to each application. By co-designing the different building blocks, which are normally present as separate chips, in one chip you obtain a system that is smaller, stronger and more economical. The latest generation of medical implants requires an integrated solution that goes beyond the sensors and actuators that can be implemented, and includes solutions for power supply, communication with external devices, biocompatibility and data processing.
Sensing and treating
By adding components such as MEMS, microfluidic sensors or photonics to conventional electronic chips, medical devices can be fabricated that are able to sense, interpret and even act or treat. Over the years, both sensing and actuation solutions have been developed at imec for a myriad of applications that could be integrated into a dedicated chip for medical purposes. One of the most successful sensing solutions is the silicon neural probe ‘Neuropixels’ for next-generation in vivo neuroscience research in small animals. The implant combines a high-density electrode array and a small footprint with best-in-class performance and ease-of-scalability.
The Neuropixels probe captures high-density electrophysiological signals.
When connecting a sensing modality like electrophysiological signals to a response such as electrical stimulation, the treatment loop can be closed. The future-generation of haptic prosthetics is a good test case for such closed-loop systems. A potential candidate is the prototype implantable chip that imec recently developed, to give amputee patients more intuitive control over their arm prosthesis. With an exceptionally high number of electrodes (64 recording and 16 stimulation electrodes, with possible extension to 128/32 electrodes), fine-grained electrical recording and stimulation can provide the patient with intuitive control of prosthesis movements combined with a feeling of touch.
Powering the implant
Implantable devices are in general very small, and physical constraints limit powering options. Many implants today are battery-powered, but when going smaller, other techniques –most likely a combination of different strategies– must be explored. In any case, ultra-low-power circuit design will be crucial. Imec routinely builds microwatt and submicrowatt circuits for wearables and especially electrophysiological sensing. The goal is to use power in an efficient way, as e.g. more sensing/actuation capabilities on a chip require more power. Therefore, reducing the power consumption and providing more power when needed, requires careful balancing. This is implemented with custom circuits tailored to the application, developed with power efficiency in mind, e.g. through hardware reuse and duty cycling.
Communicating with the implant
Once a device is implanted in the body, communication with the device is needed to track and trace its status, and receive sensor data and warnings when an action is required. Ultra-low-power radio transceivers are specifically targeting emerging power-limited and volume-constrained applications, such as ingestibles, wearables and implants. Imec has a portfolio of ultra-low-power wireless IP, including 400MHz radio frequency transceivers, designed for both on-body and in-body communications. There are also IC databases available to build a custom chip with wireless communication capabilities for implant devices.
Imec’s ultra-small-volume 400MHz radio including antenna, on a test board.
Another wireless communication technology is Bluetooth Low Energy (BT/BLE). The advantage is that BT/BLE can connect to standard off-the-shelf devices, such as a smartphone or a smartwatch. That way, the patient can check the status of his/her implant and receive alarms, while the data can be easily transferred over the internet to a medical professional. Imec’s most recent BT/BLE radio transceiver achieves a four times better power consumption than state-of-the-art products. Moreover, with a small size and low bill of materials, low-cost solutions could move towards leave-behind sensors and ‘disposables’.
Biocompatibility
When a device is implanted, there is always a distinct reaction of the body’s immune system to the ‘foreign’ object. With device miniaturization, and by providing a ‘biomimetic’ device encapsulation this reaction can be reduced. At the same time, electronic devices need to be isolated from the body to prevent corrosion an ultimately device failure. This can be achieved by encapsulating the implant using bi-directional diffusion barrier materials that stop infiltration of fluid and ions into the device, as well as prevent diffusion of toxic device materials into the body. The packaging is an integral part of the medical device and should be co-developed early in the design phase, e.g. to accommodate specific form factors or location of feedthroughs. A variety of packaging solutions and material testing protocols are heavily researched to solve the specific needs of the implant.
The intrafascicular implant to control a prosthetic arm features a dedicated chip encapsulation resulting in an ultrathin flexible device.
Data handling
An implantable device would greatly benefit from implementing machine learning algorithms to manage the large data streams and make sense of the data, but such a low-power sensor has limited resources. Recently, considerable attention ‘Tiny AI’ – a high-potential area of AI that paves the way for always-on devices capable of performing on-device sensor data analytics at extremely low power. It allows for the implementation of (part of) the machine learning techniques on the sensor data already at the device level or ‘the edge’, i.e. the wearable or the implantable. This has significant advantages. When parts of the data are combined or screened for important events on the implantable itself, this will save energy. Moreover, through tiny AI, the data can be anonymized immediately on the sensor, without other devices in between.
Want to know more?
- These were just a few highlights from the white paper entitled “Technologies for next-generation implantable devices. Small, smart and connected”. To learn more about all technologies in imec’s portfolio: download our white paper here.
- For user information on the Neuropixels probe (research purposes only), visit their dedicated website.
