Research
Research
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Our multidisciplinary research develops theoretical foundations and engineering platforms for optical, electrical, and mechanical technologies that can seamlessly integrate with the human body. These biomedical microsystems advance understanding of biology and generate high-quality patient data to accelerate discovery, diagnosis, and treatment.
To build miniaturized devices, we span key areas of biomedical sensor and system design, including mixed-signal integrated circuits (ICs), micro/nanofabrication, photonics, MEMS, system-level modeling, and hardware–software co-design. We combine optics, ultrasonics, and electromagnetics with IC design and microfabrication to unlock new capabilities for monitoring, diagnostics, and therapeutics, with an emphasis on low-power, miniaturized multimodal sensors and systems.
Application areas include medical imaging and sensing, image-guided interventions, wearable biomagnetic sensing, and wearable and implantable biosensing and neural interfaces.
Current Projects
Photoacoustic and Ultrasound Imaging
There is a need for minimally invasive in vivo imaging technologies that can provide microscopic assessment of cancer, where early detection and treatment are critical for patient survival. We are developing a photoacoustic imaging (PAI) system featuring a miniaturized, flexible, disposable probe designed to integrate into current clinical workflows. The system leverages an acousto-optical detection module enabled by microfabricated photonic devices, silicon photonics, and integrated circuits (ICs), along with all-optical readout, system-level integration, and image reconstruction algorithms. It is designed to deliver high-resolution imaging at clinically relevant depths. Lung nodule assessment will serve as the initial proof-of-concept application, with straightforward adaptation to other clinical areas such as image-guided interventions.
This project is supported by ARPA-H and is conducted in collaboration with the University of Washington, Tufts University, Brigham and Women’s Hospital, and the Dana-Farber Cancer Institute.
Photonic Sensors
Cardiovascular, cancer, and neurovascular conditions are among the leading causes of death worldwide, and improving minimally invasive care depends on better sensing and guidance during procedures. Fiber-based optical sensors can improve the safety and effectiveness of minimally invasive interventions by enabling enhanced diagnosis and therapy. We develop miniaturized fiber sensors that combine photonics with RF-field sensing to support monitoring and guidance during image-guided procedures. Our advances will enable optical RF sensors for safe, real-time tracking of interventional devices such as catheters and needles. To translate this capability to the clinic, we are integrating these sensors with a clinical MRI scanner so their signals can be incorporated directly into MR imaging during interventions. For more information, see our proof-of-concept paper. This project is conducted in collaboration with Boston Children’s Hospital.
Wireless Wearable and Implantable Systems
Continuous monitoring of physiological biomarkers can improve diagnosis and treatment across major diseases, critical care, and surgery. We develop miniaturized wireless microsystems for reliable sensing on and in the body. Our research focuses on advancing optical and multi-modal (e.g., ultrasound and electromagnetic) power delivery and data telemetry links. We integrate these links with sensors and mixed-signal integrated circuits (ICs). These technologies enable wearable and implantable platforms for neural recording and stimulation, as well as chemical and biophysical biomarker monitoring. Selected work: Wireless implantable oxygen monitoring (Nature Biotechnology; ISSCC; UFFC; Springer Nature).
News: Tiny wireless implant detects oxygen deep within the body
Biomagnetic Sensing
Biomagnetic sensing offers a noninvasive window into the body’s electrical activity by measuring the ultra-weak magnetic fields produced by physiological currents. This capability enables applications such as cardiac monitoring, brain imaging, and neuromuscular diagnostics. We are developing a new biomagnetic sensing approach to enable portable biomagnetic measurements with sub-femtotesla sensitivity across the physiological frequency range. Our goal is to operate in unshielded environments without magnetically shielded rooms or bulky enclosures. The system integrates a miniaturized magnetic field sensor with CMOS integrated circuitry and photonic components to deliver high sensitivity in real-world settings. Target applications include detecting biomagnetic signals from the heart, brain, muscles, and peripheral nerves.
Previous Projects
Microfabricated Optical Devices for Biomedical Applications
Continuous monitoring of voltages is of great interest in several applications. As an example, we recently demonstrated the first millimeter-scale, low-Q optical voltage sensor capable of transducing electrical signals into an optical readout using standard microfabrication techniques for grid applications [Optics Express (2021)]. We then demonstrated a high-Q, CMOS-compatible piezoelectric-based optical modulator that enables establishing an optical data uplink to wireless implants [Optics Express (2022)]. The modulator acts as a pF-scale capacitor, requires no bias voltage, and operates at CMOS voltages of down to 0.5V, avoiding the drawbacks of existing devices used for optical communication with implants. We believe this technology would provide a path toward the realization of sub-mm scale wireless implants for use in bio-sensing applications.
Low-power Integrated Circuits
Building minimally invasive wireless implant systems requires ultra-miniaturization of the implant to minimize tissue damage and hence enable chronic use of the implant. This mainly imposes limits on the antenna size and thereby the amount of power harvested by the implant, which in turn limits the power consumption of the implant integrated circuit (IC). To overcome this problem, we develop low-power mixed-signal ICs through innovations in circuit design and architecture for ultra-small, mm- or sub-mm scale, implants. Recently, we developed a state-of-the-art mixed-signal IC fabricated in a TSMC 65 nm LP CMOS process to build an oxygen sensor implant. The sensor implant operates on the same readout principle as most wired luminescent sensors, but with competitive or better resolution and the lowest power consumption of any system ever demonstrated by a wide margin. The implant IC details were presented at the ISSCC Conference (2020).
Ultra-low-power Microsystems via an Integrated CMOS-MEMS Platform
We demonstrated near-zero power monolithic CMOS-MEMS piezoelectric devices [Transducers (2017)]. The integrated devices were fabricated by wafer-level eutectic bonding of MEMS to CMOS. The close integration of CMOS electronics with MEMS sensors enabled minimizing the package size and provided lower electrical parasitics, improving the device sensitivity. Such monolithic integration can be used to develop ultra-low-power, ultraminiature, implantable medical sensors and devices. This can enable the development of high-performance microsystems with capabilities for use with minimal tissue damage.
Wireless Power and Data Transfer for Ultraminiature Implantable Medical Devices
Acoustic links for implantable medical devices (implants) have gained attention primarily because they provide a route to wireless deep-tissue systems. The miniaturization of the implants is a key research goal in these efforts because smaller implants result in less acute tissue damage. Implant size in most ultrasonic systems is limited by the piezoelectric bulk crystal used for power harvesting and data communication. Further miniaturization of the piezocrystal degrades system power transfer efficiency (PTE) and data transfer reliability. We developed a new method for packaging the implant piezocrystal. The method maximizes PTE and information transfer across the acoustic link, enabling the design of ultra-efficient acoustic links for ultrasonic implants; this provides a path toward the further miniaturization of these implants to sub-mm scales [IEEE T-UFFC (2021)].
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