The Head and the Heart: UC San Diego Engineers Devise Neural and Cardiac Sensors

February 05, 2022 by Ikimi .O

UC San Diego's electrical engineering department has announced a number of feats, from neural sensor grids to PMIC innovations.

Recently, researchers at the University of California San Diego (UCSD) published studies on areas such as electrophysiological devices and power management integrated circuits (PMICs). How might some of this work underway affect industries across the professional electrical engineering—and medical—space? 


Brain Signal Processing with Novel Sensor Grids 

Platinum nano-rod grids (PtNRGrids) are nanoscale platinum rods that researchers incorporate into electrocorticographic devices—devices that measure electrical activity in the brain using electrodes on the cerebral cortex. PtNRGrids are said to offer relatively higher spatial resolution and cortical coverage to monitor brain signals more efficiently than conventional platinum-based sensors. Unlike existing platinum sensors, PtNRGrids have a larger sensing surface area, making them more sensitive to brain activities, such as neuron firing.

These nanoscale grids are the basis of recent UCSD research on brain signal recording and processing. Electrocorticography (or ECoG) is a tool neurosurgeons leverage when performing sensitive medical procedures such as brain tumor removal and epilepsy treatment in patients immune to drugs and other forms of treatment. In the procedure, surgeons incorporate several sensor grids on the surface of the brain to record brain activity.  



PtNRGrids embedded on a flexible biocompatible substrate called parylene. Image used courtesy of UCSD

A key challenge with conventional ECoG grids is the low number of sensors, which limits how precisely neurosurgeons can identify defective brain regions due to tumors and other neurological issues. However, with novel PtNRGrids developed by a UCSD team of engineers, neurosurgeons, and medical researchers, neurosurgeons can access higher ECoG grid resolution than is currently obtainable for brain signal monitoring.

A UCSD press release explains that this high ECoG grid resolution is designed to better preserve normal functioning brain tissues while eliminating defective ones during complex brain surgical procedures. The research team made these improvements to conventional ECoG grids by harnessing the capabilities of platinum-based nanorods.


The grids are densely packed

The grids are densely packed with either 1,024 or 2,048 embedded ECoG sensors. Image used courtesy of UCSD

The team used a soft, transparent, and highly-flexible substrate known as parylene to embed thousands of PtNRGrids in proximity to each other. This substrate reduced significant electrical interference, improved signal quality, and stabilized PtNRGrid connection with the brain's surface. Finally, the researchers manufactured the grids with small, ring-shaped holes that allow the grids to safely displace spinal fluids, creating a better interface between the brain's surface and the sensor grid.


Pop-up Sensors Detect Heart Diseases in Record Time 

Another group of researchers at UC San Diego recently announced the discovery of a pop-up electronic sensor that can efficiently detect heart diseases by monitoring the behavior of single and multiple heart cells. This sensor pokes into cells without causing any damage to them to detect the presence of both internal and external electrical signals. It then measures their traveling speed in a single heart cell, between multiple heart cells, and within the cells of 3D tissues.

With this sensor, cardiologists may more efficiently diagnose heart diseases such as heart attack, arrhythmia, and cardiac fibrosis by detecting irregular signal propagation between different cells.


Pop-up sensor interfacing with heart cells

An illustration of the pop-up sensor interfacing with heart cells. Image used courtesy of UCSD


The researchers incorporated an array of 3D microscopic field-effect transistors (FETs) into the design and manufacture of their new sensor device. They also accounted for safety by doping the FETs in a phospholipid bilayer, eliminating the likelihood of the body perceiving them as a foreign substance.

According to their publication in Nature Nanotechnology, the team built the 3D FET array by first fabricating the FETs into 2D shapes, bonding specific points of the shapes onto a pre-stretched elastomer sheet, and then loosening the sheet. This process resulted in a buckled device and caused the FETs to fold into a 3D-array structure that can easily penetrate cells.


3D FET array structure

2D FET shapes pop up to a 3D FET array structure. Image used courtesy of UCSD


While this device was designed specifically for heart muscle cells and cardiac tissue, the team believes it can monitor electrical signals between organelles in various cell structures—making it potentially useful for novel drug testing.


PMIC Research Collaborations 

Beyond its advances in medical technology, UC San Diego also recently announced its membership in the Power Management Integration Center (PMIC). This center is part of a larger Industry-University Cooperative Research Centers (IUCRC) program that focuses on the performance of power electronics. To this end, UCSD and Dartmouth are collaborating with other industry players, including Infineon Technologies, Analog Devices, Intel, Qualcomm, and Allegro MicroSystems. 

The goal of this partnership is to design and create circuit topologies and apply energy storage in a way that maximizes efficiency and minimizes device footprints and costs. The Center intends for this next generation of devices to boost system reliability, robustness, and performance across several electronic applications, including consumer, automotive, and industrial.


Ziyu Xia presents his project

Funded by PMIC, Ph.D. student Ziyu Xia presents his project titled “An Integrated 5:1 DC-DC converter.” Image used courtesy of Andrila Hait and Dartmouth University

Further, the Center aims to foster research collaborations relevant to industry needs, including the development of power management ICs, discrete power converters, and circuit topologies that exhibit high efficiencies and power densities. The Center also hopes to design, optimize, and control an extended range of converter architectures for the high-frequency operation of small passive components.

PMIC plans to leverage the financial investments of member institutions to develop a knowledge base and workforce that will improve the capabilities of power electronics on a short- and long-term basis.



Have you heard of any interesting research coming out of your alma mater? We'd like to hear about it in the comments below.