UCLA Engineers Discover Permanent Fluidic Magnets for Liquid Bioelectronics
Jun Chen Lab/UCLA
Schematic of a new UCLA-developed permanent fluidic magnet for liquid bioelectronics that can be injected into an organ to monitor its activity
Fluidic magnets open the door to a variety of new technologies, including bioelectronics that can change the way we look at health and medicine. Now a team of UCLA engineers has developed a permanent fluidic magnet that can be used in liquid bioelectronics. The advancement has many applications such as organ monitoring during medical procedures, voice sensing and recognition, as well as ambulatory cardiac monitoring.
Published last spring in Nature Materials, the UCLA study led by Jun Chen — an associate professor of bioengineering at the UCLA Samueli School of Engineering — describes the creation of the permanent fluidic magnet, or PFM. The team developed the material by decoupling the fluid’s stability from Brownian motion, which is the random movement of magnetic nanoparticles suspended in liquid. Brownian motion typically causes magnetization relaxation that prevents permanent magnetism. By using non-Brownian magnetic particles, the team was able to achieve long-term, stable fluidic permanent magnetic materials through the creation of a 3D-oriented and ramified magnetic network — a branching tree of particles suspended within the carrier fluid.
“Our permanent fluidic magnet-based liquid bioelectronics gain previously unobtainable conformality, generalizability, reconfigurability, injectability and retrievability compared to conventional solid bioelectronics,” said Chen who leads the Bioelectronics Research Group at UCLA. “The new PFM and PFM-based liquid bioelectronics will open the door to new advances in physics and medicine.”
The team demonstrated the technology by measuring heart activity after injecting the liquid bioelectronics into the heart with a minimally invasive syringe. The PFM device was able to detect characteristic heart activity such as atrial contraction and depolarization.
In addition to sensing heart rhythms, the team’s latest PFM platform — an ultra-conformable liquid-tissue interface — can be used to monitor any organ without being influenced by motion or external mechanical disturbances. The material is also easily injectable and retrievable, allowing for its use in minimally invasive surgery. PFM itself may also be used to create new classes of colloidal materials — materials in which microscopic objects are suspended in another substance. The research suggests that PFM can also provide insight into phase separation in dipolar and multipolar fluids and contribute largely to other structural fluids and colloidal gels.
According to the researchers, previous magnetic materials were either permanent but rigid in form, or fluidic but not permanently magnetic. The new PFM is both fluidic and magnetic permanently, making it more flexible in application and more sensitive for bioelectronic applications than its solid, non-permanent counterparts.
Since their initial proof-of-concept prototype, researchers from Chen’s lab have already invented two additional bioelectronics utilizing the new PFM material. The first, detailed in a study published last fall in Nature Electronics, is a liquid acoustic sensor for voice recognition. The sensor has the ability to filter background noise or motion artifacts — distortions caused by body movement during a procedure. The device also features a high signal-to-noise ratio of 69.1 decibels. The sensor overcomes challenges faced by conventional solid acoustic sensors, such as poor skin conformability, limited sensitivity, narrow pressure detection range and instability against motion artifacts.
The new sensor works with a machine-learning algorithm, which could be used to create a wearable voice-recognition patch that offers an accuracy of 99% in a noisy environment. It could serve as an alternative communication method for those with vocal impairments by detecting throat movements and translating them into audible voice or text.
Aside from recognizing voices, the sensor has potential additional applications including monitoring and assessing vocal health, detecting changes in voice patterns and identifying potential vocal disorders.
The team’s latest PFM-based bioelectronic was discussed in a study published October in Nature Communications. The researchers developed and tested a reconfigurable liquid cardiac sensor that can be used for ambulatory cardiac monitoring, which monitors the heart over longer periods while the individual goes about their daily routines.
The liquid sensor is capable of adapting to the dynamic nature of skin, overcoming challenges that can cause gaps between the sensor and skin in conventional solid sensors. PFM, made from alginate solution, can form a seamless interface to the wrinkles and creases on the skin surface facilitating ambulatory cardiac monitoring unhindered by motion artifacts or interference from other biological activities. The sensor allows uninterrupted health monitoring to help capture any irregularities or abnormalities that may occur intermittently or during daily activities.
The Nature Materials study was conducted in collaboration with Song Li, Chancellor’s professor of bioengineering at UCLA Samueli and director of the Song Li Lab. The Nature Electronics paper was written with Pirouz Kavehpour, a professor with joint faculty appointments in mechanical and aerospace engineering and bioengineering at UCLA Samueli. Kavehpour leads the Complex Fluids and Interfacial Physics Laboratory.
Undergraduate student Justin Li and graduate student Jing Xu are authors on both the Nature Materials and Nature Electronics studies. Undergraduate student Aaron Li is an author on both the Nature Electronics and Nature Communications paper. Graduate student Xun Zhou and postdoctoral scholar Yihao Zhou are authors on all three papers. All of them are members of Chen’s lab.
Yang Song, formerly a postdoctoral scholar in Li’s lab, is one of the Nature Materials paper’s authors. Other authors of the paper are UCLA Samueli graduate students Trinny Tat and Guorui Chen — both members of Chen’s lab. The work was funded by the American Heart Association, the Brain & Behavior Research Foundation, the West Coast Consortium for Technology & Innovation in Pediatrics at Children’s Hospital Los Angeles, the National Institutes of Health and the UCLA Samueli School of Engineering.
Other authors of the Nature Electronics paper are undergraduate students Shreesh Karjagi, Edward Hahm and Lara Rulloda — all members of Chen’s lab — as well as graduate student John Hollister, a member of Kavehpour’s lab. The research was funded by the American Heart Association, the Brain & Behavior Research Foundation, the National Institutes of Health, the U.S. Office of Naval Research and the UCLA Samueli School of Engineering.
For the Nature Communications paper, other authors from Chen’s lab are undergraduate student Marklin Dallenger, and graduate students Shaolei Wang and Songyue Chen. Additional UCLA undergraduate students William Kwak, Yuqi Zhang and Allison Lium are also authors on the paper. The work was funded by the same organizations that supported the team’s research published in Nature Electronics, with additional funding from the National Science Foundation.