Lower Power, More Reliable Memory, and More Ambitious Applications: Implantable Tech Roundup

Implantable medical technologies present a host of unique challenges to device designers. Solving these challenges requires unique solutions. Here's a snapshot of some of the most recent developments in the implantable tech space.

Since time immemorial, people have decorated themselves with tattoos and any numbers of types of piercings such as earrings and studs. But those were external, merely impinging on the skin. But now, we go beneath the skin to our innermost precincts, and the merging of man and machine begins.

So, are we on our way to becoming cyborgs? Maybe not, but implantable technology is becoming more common, especially recently as implantables find increasing use across non-medical applications. 

Here's a look at some interesting developments, trends, and products in the implantable technology space.

A Battery that Runs on Glucose

Whether they're actively pumping blood or simply gathering data, implantable devices need power to operate. Using batteries is problematic because, when they need to be replaced, minor—or sometimes not so minor surgery—is required. Lithium-ion batteries are still the power source of choice for devices such as cochlear implants and pacemakers. In this sense, wireless charging has proven to be a boon, allowing devices like the Optimizer Smart to recharge batteries while still implanted. 

Another possible solution, however, is a fuel cell that runs on glucose, the body’s own fuel, that is always abundantly present in the bloodstream.

Researchers from the Georgia Institute of Technology and Korea University have employed gold nanoparticles assembled onto cotton to build an improved fuel-cell electrode.

This development allowed the research team to improve the link between the electrode and enzyme that actually oxidizes the glucose, thus removing one of the major impediments standing in the way more efficient biofuel cells.

 

Viewing the details of the cotton-based electrode via an electron microscope. Image from the Georgia Institute of Technology and Korea University

 

It is believed that the use of cotton fiber will improve the fuel cell’s compatibility with the human body and also increase the device’s longevity within a living person. The team reports that a power output of 3.7 milliwatts per square centimeter has been recorded. That’s a lot of power and higher peak requirements could be attained through storage within supercapacitors located within the medical devices to be powered.

 

Nanoscale closeups of the cotton fibers. Image from the Georgia Institute of Technology

 

The concept of harvesting the body's own energy isn't a new one. Over the years, researchers have investigated powering devices with body heat, piezoelectricity, and a series of chemical reactions generated within the body, itself. This April, for example, a device powered by enzymatic biofuel was successfully implanted into a rabbit and monitored in vivo for two months, signaling a serious advancement in this form of implantable device.

Whether glucose-fueled batteries make it to the mainstream of implantable devices depends on their utility in further testing and whether they can pass the rigorous testing associated with medical devices in the USA.

Better Memory for Portable Medical Devices

The puzzle of powering portable devices gets a lot of attention, and for good reason. But the challenges of implantable devices extend beyond designing unintrusive power systems. Low-power memory storage is also a pain point for devices expected to function over long periods of time. Even if a device isn't necessarily gathering environmental data for medical professionals to analyze, they are often gathering data on its own operations for analysis by engineers. 

Cypress Semiconductor recently announced its low-power data-logging memory solution, named Excelon™ LP F-RAM. FRAM is ferroelectric random access memory, often posed as an alternative to flash memories such as NOR or NAND flash.

 

The Excelon FRAM GQFN package. Image from Cypress Semiconductor

 

Cypress released this particular data logging product with several applications in mind, including industrial PLCs and autonomous vehicles, but its focus has arguably been portable medical devices. 

"Its instant writes and ultra-low power modes maximize system battery life with unlimited endurance for long-term reliable data logging," says Sonal Chandrasekharan, Senior Director of their RAM business unit, in a video. That reliability is what Cypress believes makes this particular product suitable for implantable applications. 

 

The simplified diagram for Cypress Semiconductor's implantable device application note. Image from Cypress Semiconductor

 

According to their press release on the subject, Cypress claims that this is the "industry's most energy-efficient nonvolatile RAM"—a notable assertion in the realm of implantables where power consumption is such a serious pain point. In the same document, Cypress claims that this FRAM solution requires "200 times less energy than EEPROMs and 3,000 times less than NOR Flash".

The Growing List of Applications for Implantables

Advancements in the power, memory, and safety of implantable devices can sometimes seem incremental. In applications, however, these advancements allow more ambitious use cases for implantable technologies. 

 

Security, Monitoring, and Identification via Implantable Chips

Implantable chips are becoming more common outside of medical applications, serving the less pressing function of convenience.

In places like Sweden, a wave of a palm with a chip inside can replace the use of RFID-embedded identification cards to give people keyless access to their homes and vehicles. A Wisconsin-based company last year took this accessibility-focused implantation a step further by stitching these chips into their security network by only allowing an employee to use their chip to access their computer if they'd already been scanned in at the door.

While some believe that being microchipped is a matter of inevitability, many others are concerned about the privacy and security implications of such practices becoming widespread.

 

Implantable Device for Congestive Heart Failure

The Optimizer Smart from Israel’s Impulse Dynamics delivers what the company describes as Cardiac Contractility Modulation (CCM) to the hearts of patients suffering from certain clinically defined stages of the illness.

 

Image from Impulse Dynamics

 

Unlike defibrillators, which send out low-energy pulses to correct errant heart rhythms, the Optimizer Smart sends out a much higher-powered jolt to the heart, forcefully directing the muscles to squeeze harder to send the otherwise trapped volumes of blood out to the body where it belongs.

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Have you designed implantable devices? What's caught your eye in the implantable space over the last year? Share your thoughts in the comments below.