Introducing a Biologically Powered Chip

The ability to add the functionality of biological systems to CMOS circuits can one day lead to creating an entirely new class of sensors.

Jul 20 2017 | By Holly Evarts

Columbia Engineering researchers have, for the first time, harnessed the molecular machinery of living systems to power an integrated circuit from adenosine triphosphate (ATP), the energy currency of life. They achieved this by integrating a conventional solid-state complementary metal-oxide-semiconductor (CMOS) integrated circuit with an artificial lipid bilayer membrane containing ATP-powered ion pumps, opening the door to creating entirely new artificial systems that contain both biological and solid-state components.

The Shepard Group focuses on mixed analog-digital CMOS integrated circuit design. (Video by Jane Nisselson)

“With appropriate scaling, this technology could provide a power source for implanted systems in ATP-rich environments such as inside living cells,” says Jared Roseman PhD’15, who led the study with Kenneth Shepard, Lau Family Professor of Electrical Engineering and professor of biomedical engineering. In Shepard’s Bioelectronics Systems Lab at Columbia, researchers are focused on exploiting silicon integrated circuits—typically used in computers and smartphones—as a platform for exploring the life sciences.

“In combining a biological electronic device with CMOS, we will be able to create new systems not possible with either technology alone,” Shepard notes. “We are excited at the prospect of expanding the palette of active devices that will have new functions, such as harvesting energy from ATP, as was done here, or recognizing specific molecules, giving chips the potential to taste and smell. This was quite a unique, new direction for us, and it has great potential to give solid-state systems new capabilities with biological components.”

Despite its overwhelming success, CMOS solid-state electronics is incapable of replicating certain functions natural to living systems, such as human senses and the use of biochemical energy sources. Living systems achieve this functionality with their own version of electronics based on lipid membranes and ion channels and pumps, which act as a kind of “biological transistor.” They use charge in the form of ions to carry energy and information—ion channels control the flow of ions across cell membranes. Solid-state systems use electrons; their electronic signaling and power are controlled by field-effect transistors.

In living systems, energy is stored in potentials across lipid membranes, in this case created through the action of ion pumps. ATP is used to transport energy from where it is generated to where it is consumed in the cell. To build a prototype of their hybrid system, Roseman packaged a CMOS integrated circuit (IC) with an ATP-harvesting “biocell.” In the presence of ATP, the system pumped ions across the membrane, producing an electrical potential harvested by the IC.

Roseman and Shepard made a macroscale version of this system, at the scale of several millimeters, to test it out. Shepard notes, “Our results provide new insight into a generalized circuit model, enabling us to determine the conditions to maximize the efficiency of harnessing chemical energy through the action of these ion pumps.”

While other groups have harvested energy from living systems, Shepard and his team are exploring how to do this at the molecular level, isolating just the desired function and interfacing this with electronics. “We don’t need the whole cell,” he explains. “We just grab the component of the cell that’s doing what we want. For this project, we isolated the ATPases because they were the proteins that allowed us to extract energy from ATP.”

The ability to build a system that combines the power of solid-state electronics with the capabilities of biological components has great promise. “You need a bomb-sniffing dog now, but if you can take just the part of the dog that is useful—the molecules that are doing the sensing—we wouldn’t need the whole animal,” says Shepard.

“Reducing any idea to practice is always filled with many challenges,” says Roseman. “This issue is compounded even further when you are paving the way in a new research area, and things can be frustrating at times when the data is slow to come. These frustrations, however, lead to an indescribable joy when you finally get things to work.”

Their work, funded by the W. M. Keck Foundation and the Office of Naval Research, was published December 7 in Nature Communications.

CMOS chips integrated with the “wet” world of biology (Photo by Jeffrey Schifman)