Low-power biomedical integrated circuits
Advances in integrated circuit technology have enabled electronic systems that can augment or even replace physiological functions. While the processing capabilities of these devices are virtually unlimited, the available energy is highly constrained. Our research combines low-power architectures with innovations in circuit design techniques to design biomedical electronics capable of ultra-low-power operation on/in the human body.
References
- S. Hsu and A. S. Y. Poon, “Optimization of sine-wave clocking for high-frequency AC-DC conversion,” IEEE Transactions on Power Electronics, 34, 391–402 (2019).
- Y. Rajavi, M. Taghivand, K. Aggarwal, A. Ma, and A. S. Y. Poon, “An RF-powered FDD radio for neural microimplants,” IEEE Journal of Solid-State Circuits, 52, 1221-1229 (2017).
- A. Yakovlev, D. Pivonka, T. H. Meng, and A. S. Y. Poon, “A mm-sized Wirelessly Powered and Remotely Controlled Locomotive Implantable Device,” Proc. IEEE International Solid-State Circuits Conference (ISSCC), San Francisco, CA, Feb. 2012.
Wireless neuromodulation platforms for small animals
Optical or electrical stimulation of neural circuits in mice during natural behavior is an important paradigm for studying brain function. Conventional systems for optogenetics and electrical stimulation require tethers or large head-mounted devices that disrupt animal behavior. Our research focuses on developing new wireless tools for activity modulation in both the brain and the periphery. Targeted technologies include wireless platforms for experiments in freely-moving animals and tiny, fully-implantable devices for controlled delivery of light or electrical pulses.
See the Animation for explanation on how self-tracking wireless energy transfer works.
References
- J. S. Ho, Y. Tanabe, S. M. Iyer, A. J. Christensen, L. Grosenick, K. Deisseroth, S. L. Delp, and A. S. Y. Poon, “Self-tracking energy transfer for neural stimulation in untethered mice,” Physical Review Applied, 4, 024001 (2015). Summary in Physics.
- K. L. Montgomery, A. J. Yeh, J. S. Ho, V. Tsao, S. M. Iyer, L. Grosenick, E. A. Ferenczi, Y. Tanabe, K. Deisseroth, S. L. Delp, and A. S.Y. Poon, “Wirelessly powered, fully internal optogenetics for brain, spinal, and peripheral circuits in mice,” Nature Methods, 12, 969-974 (2015).
- A. Poon, “A new kind of wireless mouse,” IEEE Spectrum, 53, 12, 26-32 (2016).
Metasurfaces
The solid immersion lens is a powerful optical tool that allows light entering material from air or vacuum to focus to a spot much smaller than the free-space wavelength. Conventionally, however, they rely on semispherical topographies and are non-planar and bulky, which limits their integration in many applications. Recently, there has been considerable interest in using planar structures, referred to as metasurfaces, to construct flat optical components for manipulating light in unusual ways. Here, we propose and demonstrate the concept of a planar immersion lens based on metasurfaces. The resulting planar device, when placed near an interface between air and dielectric material, can focus electromagnetic radiation incident from air to a spot in material smaller than the free-space wavelength.
References
- J. S. Ho, Y. Tanabe, A. J. Yeh, S. Fan, and A. S. Y. Poon, “Planar immersion lens with metasurfaces,” Physical Review B, 91, 125145 (2015).
Wireless power transfer to microimplants
Medical electronics are capable of precisely monitoring or modulating activity in the human body, and thus hold promise for treating a broad range of diseases. To implant electronic devices in the body, they need to be miniaturized and powered wirelessly across complex biological tissue. We are developing a new method of electromagnetic energy transfer, termed midfield powering, to power devices at the scale of a millimeter or less anywhere in the body, including the heart and the brain. Our approach spans fundamental studies of wave-tissue interactions, development of new electromagnetic structures, and experiments in both computational and animal tissue models.
See the Resources page for additional information and downloads for using this method.
References
- J. S. Ho, A. J. Yeh, E. Neofytou, S. Kim, Y. Tanabe, B. Patlolla, R. E. Beygui, and A. S. Y. Poon, “Wireless power transfer to deep-tissue microimplants,” PNAS, 111, 7974-7979 (2014). Summary in Physics Today.
- S. Kim, J. S. Ho, and A. S. Y. Poon, “Midfield wireless powering of subwavelength autonomous devices,” Phys. Rev. Lett., 110, 203905 (2013).
- S. Kim, J. S. Ho, L. Y. Chen, and A. S. Y. Poon, “Wireless power transfer to a cardiac implant,” Appl. Phys. Lett., 101, 073701 (2012).