(2ez) Next-Generation Bioelectronics Enabled By Single-Crystalline Inorganic Semiconductor Membranes

I am currently a postdoctoral associate at the Massachusetts Institute of Technology (MIT). I have an extensive research background in developing wearable and implantable biomedical systems via nanofabrication of electronic/ optoelectronic/photonic/mechanical devices that are based on ultrathin and high-performance inorganic semiconductor membranes. Throughout my research career, I have aimed to invent game-changing biomedical technologies based on device and materials innovation, which has allowed me to publish in renowned journals such as Nature, Science, Nature Nanotechnology, and Nature Biomedical Engineering.

I received my Ph.D. in Chemical Engineering from the University of Illinois at Urbana-Champaign (UIUC) in 2018. Under the supervision of Prof. John A. Rogers, I demonstrated implantable sensors for monitoring pressure, temperature, blood oxygenation, and neural activity inside the brain by using bioresorbable materials such as nano-membranes of silicon, silicon oxide, and magnesium. The fabricated device will, following a period of use in vivo, naturally disappear in biofluids over time, eliminating the need for surgical extraction [1-3]. The use of nano-membranes of single-crystalline silicon, the most widely used semiconductor material for consumer electronics today, uniquely enables implantable sensors with unprecedented sensitivity, long-term stability, and resorbability, offering the potential to transform conventional post-surgical patient monitoring paradigm.

Since joining Prof. Jeehwan Kim’s group at MIT as a postdoc, my research has focused on the development of wearable bioelectronics for monitoring health-related signals (pulse/heart rate, UV exposure, sweat composition, etc.) and for augmented and virtual reality (AR/VR) displays using single-crystalline compound semiconductor membranes. The ability to produce inorganic compound semiconductor devices – such as light-emitting diodes (LEDs), photodetectors, and acoustic wave-based wireless sensors – that are only about 1-μm-thick offers unique opportunities to create flexible bioelectronics that are ultralight, flexible-like-skin (hence, known as ‘electronic skin’), and can be attached conformally on the skin for extended periods of time to continuously collect biophysical/chemical data with high sensitivity [4, 5]. Also, these ultrathin device layers can be vertically stacked to form 3D-integrated bioelectronics with unprecedented device density and multifunctionality, which can yield critical advances in various technologies including near-eye AR/VR displays [6], brain-machine interfaces, etc.

Research Interests

My research interests include the development of new classes of flexible and 3D-integrated bioelectronics based on single-crystalline membranes (III-V, III-N, Si, complex oxide) that can be obtained via layer transfer techniques. Layer transfer refers to a set of techniques used to separate single-crystalline device layers from the wafers upon which they’re grown. These techniques can yield devices with a wide range of electronic/optoelectronic/mechanical/magnetic properties, perfect crystallinity, and ultrathin form factor, which make them ideal building blocks for (i) high-performance flexible devices that can be attached conformally on the surfaces of soft, curved, and elastic tissues such as the skin or the brain to reliably collect, and wirelessly transfer, physiological data, and (ii) 3D-integrated systems that achieve high device density and novel functionality by stacking layers of different materials and devices (Fig. 1). I believe that my broad expertise in layer transfer, semiconductor materials and devices, heterogeneous integration techniques, and live animal studies will allow me to develop transformative device technologies in up-and-coming research fields such as remote healthcare, brain-machine interface, and augmented/virtual reality (AR/VR). Below, I summarize a more detailed research plan that I will pursue.

1. Flexible Bioelectronics: My past research has involved two different layer transfer techniques: 2D material-based layer transfer (2DLT) and chemical-based layer transfer (commonly known as epitaxial lift-off or ELO), which uses mechanical force or chemical etching to separate single-crystalline ‘epilayers’ from substrates (Fig. 2a,b). My expertise in both techniques gives me unique capability to access the entire library of electronic, photonic, mechanical, and magnetic devices – such as strain, temperature, and light sensors, MEMS sensors and actuators, diodes/transistors, and light emitters (LED, laser), e.g. – as well as coupled material properties – such as piezoelectric/resistive, magnetostrictive/optic, thermoelectric/ magnetic, and spintronic properties. Bonding or encapsulating these device layers with flexible polymers can yield various types of skin-mountable or implantable biomedical devices (Fig. 2c, d). More specifically, I’m interested in developing: (i) micro-LED patches for skin regeneration, health monitoring, and cancer treatment; (ii) wireless chemical sensors for analyzing stress hormones or volatile organic compounds in sweat, breath, and saliva; and (iii) bioresorbable sensors integrated with neuromorphic computing device for closed-loop biosensing and treatment inside the body.

2. 3D-Integrated Bioelectronics: Vertical integration of different types of single-crystalline semiconductor membranes produced by layer transfer can produce novel functional platforms with unprecedented device density and capability. I envision that this approach has the potential to provide critical advances in the following biotechnologies: (i) optoelectronic-based brain-machine interface via vertically integrated LEDs and photodetectors, to achieve high-resolution, cell-type-specific, multi-site, and bi-directional neural interface (Fig. 3a); (ii) magnetoelectrically-activated wireless stimulators with ultra-small size for accelerated regeneration of damaged nerves (Fig. 3b); (iii) artificial intelligence (AI) chip stacked on drug delivery microneedle patches for advanced pain management (Fig. 3c); and (iv) fully immersive AR/VR displays consisting of vertically stacked RGB micro-LEDs and CMOS backplane with extremely high-pixel densities (Fig. 3d).

Teaching Interests

My teaching interests include all courses in Chemical and Biomolecular Engineering, as well as those regarding devices and materials, with a particular focus on bioelectronic systems. My academic backgrounds (B.S. and Ph.D. in ChemE) has prepared me to teach ChemE courses including Thermodynamics, Heat and Mass Transfer, Separations, Kinetics and Reactor Design, etc. My research backgrounds in micro/nanofabrication, electronic/optoelectronic/photonic/MEMS devices, inorganic semiconductor materials (III-V, III-N, Si), and bioresorbable materials (insulator, metal, polymer) will allow me to also easily teach courses in Semiconductor Electronics, Electronic Circuits, MEMS Devices and Systems, and Lasers and Photonics, etc.. I'm also interested in developing new graduate level courses: Biomedical Device Design and Application, where I will discuss the materials, designs, implantation procedures, and applications of biomedical implants based on electronic, optoelectronic, chemical, and mechanical principles; and Physics of Neural Interfaces, where I will discuss the different types of neural recording and stimulation technologies based on electrical, optical, and magnetic-based approaches – their fundamental working principles, materials, and probe designs. In all of these cases, I believe that my broad academic and research backgrounds will allow me to provide students with unique perspectives and examples to help expand their knowledge basis.

References

[1] J. Shin et al. “Bioresorbable pressure sensors protected with thermally-grown silicon dioxide for the monitoring of chronic diseases and healing processes,” Nature Biomedical Engineering 3, 37–46 (2019)

[2] W. Bai, J. Shin (co-first) et al. “Bioresorbable photonic devices for the spectroscopic characterization of physiological status and neural activity,” Nature Biomedical Engineering 3, 644–654 (2019)

[3] J. Shin et al. “Bioresorbable optical sensor systems for monitoring of intracranial pressure and temperature,” Science Advances 5, eaaw1899 (2019)

[4] H. Kim, S. Lee, J. Shin (co-first) et al. “Graphene nanopattern as a universal epitaxy platform for single-crystal membrane production and defect reduction,” Nature Nanotechnology 17, 1054–1059 (2022)

[5] Y. Kim, J. M. Suh, J. Shin (co-first) et al. “Chip-less wireless electronic skins by remote epitaxial freestanding compound semiconductors,” Science 377, 859–864 (2022)

[6] J. Shin et al. “Vertical full-colour micro-LEDs via 2D materials-based layer transfer,” Nature 614, 81–87 (2023)