CIRC Lab: What We Do & What We Aim to Do
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Research Field
Systems Realized by Circuits
Bridging theory to real-world implementation, from ideas to silicon.
Most modern systems are realized through circuits. Inside these systems, printed circuit boards (PCBs) interconnect and control various functional components. To achieve greater miniaturization and higher performance, these discrete components must be integrated into a single integrated circuit (IC), composed of millions of transistors.
IC: The Core of Implantable Medical Devices
IMDs, such as cochlear implants, retinal implants, neural recording devices, and deep brain stimulation systems, are placed inside the human body or brain and therefore require ultra-small size and extremely low power consumption. These stringent requirements can only be achieved through advanced IC design.
IMDs require essential blocks: 1) Wireless Power Transfer, 2) Forward Data Telemetry, 3) Backward Data Telemetry, 4) Neural Stimulation. Additional functionalities include neural recording, on-chip processing, and other system-level integration components.
1. Wireless Power Transfer (WPT)
IMDs can be powered by implanted batteries. However, batteries are typically bulky and require periodic surgical replacement, imposing a significant clinical burden. As an alternative, wireless power transfer (WPT) using implantable inductive coils offers a practical solution. A WPT system generally consists of two key blocks: a power amplifier (PA) outside the body and an AC–DC rectifier inside the body. Our research focuses on maximizing the efficiency of each block as well as optimizing overall system efficiency. In addition, we investigate optimization of coil structures while considering both implantation constraints and power transfer performance.
Check out two examples of AC–DC rectifier topologies that provide multiple regulated outputs without the need for a subsequent low-dropout regulator (LDO), thereby improving power conversion efficiency. The proposed systems are named SIMO R3 and ER4, respectively.
2. Forward Data Telemetry
In IMDs, operating settings such as stimulation intensity and the number of active channels often need to be adjusted, and these updates are performed using command data sent from outside the body. In such cases, forward data telemetry delivers these commands from outside the body to the inside while maintaining wireless power transfer simultaneously. Our research focuses on minimizing the power consumption of the telemetry block and ensuring robust data tranfer, even under increased coil separation and angular misalignment.
Check out an example of a forward data telemetry topology that eliminates the conventionally required analog envelope detector and replaces it with a fully digital detector to reduce power dissipation. The proposed system is named EDL Forward Telemetry.
3. Backward Data Telemetry
In many cases, data acquired by IMDs, such as neural recording data, must be transmitted outside the body for further processing. In such situations, backward data telemetry is required to send the acquired data from inside the body to the outside while maintaining wireless power transfer. Our research focuses on increasing the data rate and lowering the bit error rate (BER). Furthermore, we investigate full-duplex data telemetry, where forward and backward data transmission occur simultaneously while wireless power transfer is continuously maintained.
Check out an example of a backward data telemetry topology that is capable of transferring reliable data regardless of whether the IMD is in sleep or active mode. The proposed system is named Hybrid-LSK Backward Telemetry.
4. Neural Stimulation
Neural stimulation, including deep brain stimulation, is required to treat neurological disorders such as Parkinson’s disease and epilepsy by targeting deep brain regions like the thalamus. In this approach, predetermined electrical charges are delivered to the target area. This stimulation is powered by the WPT block and operates together with forward and backward data telemetry. Our research focuses on improving overall system efficiency, including both AC-DC rectifier and neural stimulation.
The example topology will be presented after acceptance of the journal paper currently under review.
We are expanding our research areas!
5. Ultrasound Neural Dust
Compared to inductive coil–based WPT with changing magnetic field, Neural Dust utilizing ultrasound offer significant advantages in achieving smaller device size and deeper implantation. First, at the same resonant frequency, an ultrasound transducer can be made substantially smaller than an inductive coil. Second, ultrasound provides superior tissue penetration due to its relatively low attenuation in water-rich biological media. This enables more efficient power delivery to deep brain or peripheral nerve targets, even at depths of several centimeters beneath the surface. In contrast, magnetic fields generated by inductive coils experience rapid attenuation as implantation depth increases.
6. Energy Harvesting
WPT methods that rely on external transmitters, such as inductive coils or ultrasound transducers, have inherent limitations. They require a continuous external power source and are often sensitive to alignment and angle variations. In addition, transmitted energy may cause tissue heating, be subject to regulatory limits on external power intensity, and require dedicated charging sessions or wearable hardware. Therefore, energy harvesting offers a compelling alternative. By capturing ambient energy directly from within the body or its surroundings—such as muscle contractions, heartbeat, or blood flow—it enables fully autonomous implantable systems without the need for external power delivery.
Note that our lab. is not limited to biomedical energy harvesting alone; we are broadly interested in other energy sources such as piezoelectric transducers, triboelectric nanogenerators (TENG), solar energy, and RF energy harvesting.
7. Bio. System-on-Chip
Our next-generation biomedical platform will feature a fully-integrated System-on-Chip (SoC) — a single sub-millimeter silicon die that combines wireless power transfer, forward/backward data telemetry, neural stimulation, low-noise neural recording, and an on-chip processor into one monolithic chip. This extreme integration will enable ultra-miniaturized, batteryless implants with minimal interconnects, drastically reduced power consumption, enhanced long-term reliability, real-time closed-loop control, and support for high-density multi-channel operation—paving the way for seamless, chronic, minimally invasive solutions across neural interfaces, cardiac devices, biosignal monitoring, and beyond.
8. Anything that can be built using circuits
We are interested in any system that can be realized through circuit design. From sensing to power management, wireless communication, and intelligent hardware systems, we explore a broad spectrum of circuit-driven technologies. Our work spans diverse application domains, including biomedical devices, IoT platforms, robotics, and next-generation energy systems.
Our motto is simple: if it can be built with circuits, we are ready to design it. Even if your idea lies beyond our current research scope, we welcome new challenges. We are always open to unexplored problems and ambitious projects that push technical boundaries. Let’s explore new concepts together and turn them into meaningful research outcomes and high-impact publications. Furthermore, we are interested in interdisciplinary collaborations that connect the IC to emerging devices and deliver high impact in both industry and academia.
CIRC Lab's Philosophy
Push the boundaries
and expand beyond limits
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