Mechanical Engineering

May 15, 2026 (Friday) 4:00pm-5:00pm
In this talk, Professor Yuan Lin will introduce their recent efforts in elucidating the role of mechanics/physics in different cellular and tissue-level processes. First, he will demonstrate that mechano-transduction via intercellular integrin complexes between the invading spheroid leader cell and mesothelial cells triggers and augments mesothelium apical constriction, which then leads to the shrinkage of mesothelial cell-cell junctions and eventually induces their rupture. At the same time, the growth of intercellular integrin adhesion causes wetting at the spheroid-mesothelium interface and induces deformation of spheroid cells, further facilitating its invasion into the mesothelium. After that, he will talk about how collective active contraction of cells and their interactions with outside dictate the pattern formation of tissues. Finally, he will show how tubulin family proteins (i.e., isotypes) regulate the microtubule accessibility for luminal proteins via the force-induced reversible protofilament separation, and ultimately mechanosensitive response of the cell.

November 27, 2025 (Thursday) 4:00pm-5:00pm
Under strain, the physical properties of semiconductors can undergo significant changes. However, bulk semiconductor crystals are usually rigid and brittle, making it challenging to achieve high strain levels. Our experiments show that by microfabricating semiconductors like silicon and diamond into micro/nanostructures, they can approach their theoretical strength and sustain ultralarge elastic deformation, opening a new pathway for deep elastic strain engineering of semiconductors via nanomechanics. To realize such strain-engineered device applications, we microfabricated single-crystalline diamond microbridge arrays and achieved sample-wide uniform elastic strains of up to ~10% under uniaxial tensile loading. This ultralarge strain significantly reduced diamond’s bandgap by >2eV or converted diamond from an indirect to a direct bandgap semiconductor, demonstrating great potential for wide bandgap semiconductors and optoelectronics. Moreover, we have extended deep elastic strain engineering to two-dimensional material systems. This includes pioneering the first tensile and shear tests on free-standing monolayer 2D materials, such as graphene, hexagonal boron nitride and Transition Metal Dichalcogenides, as well as their homo- and heterostructures (e.g., twisted bilayer graphene). These studies not only reveal the anomalous nanomechanical properties of 2D materials, but also underscore the potential of elastic strain engineering (up to ~6%) for tuning 2D electronic and optoelectronic devices.

October 9, 2025 (Thursday) 4:00pm-5:00pm
Improving indoor air requires addressing source control, ventilation, and filtration. This presentation explores filter performance from both aerosol science and building science perspectives with a focus on how theoretical and laboratory-tested filtration efficiencies translate to filtration performance in real buildings. The removal of particulate matter is only part of the filtration story. Filters also have a variety of secondary consequences including emissions of gas-phase compounds and complicated impacts on energy use. Some of these secondary effects may have a positive impact, including the ability of filters to offer insight on air quality through filter forensics, the analysis of the particles that accumulate on the filter. Several examples of filter forensics for disease surveillance, exposure assessment, and ambient air quality are used to illustrate the hidden value in used filters. The COVID-19 pandemic further increased the attention paid to central and portable filtration in buildings and this presentation assesses new challenges and opportunities that arise from this renewed focus.

June 27, 2025 (Friday) 4:30pm-5:30pm
This talk will present the latest advancements from Professor Chan’s research team and his startup company Brainsmart, dedicated to developing minimally invasive brain-computer interface (BCI) technologies for stroke rehabilitation and neurological recovery. His team focuses on flexible neural probes and high-density ECoG arrays that can be implanted without craniotomy, offering safer options for high-risk patients. Professor Chan will highlight their recent results in decoding neural signals related to hearing perception and motor intentions, and discuss how these findings contribute to future neuroprosthetic applications. The talk will also cover our pathway from technology development to clinical translation, aiming to enhance functional recovery and quality of life for patients.

December 19, 2024 (Thursday) 4:30-5:30pm
To enhance the thermoelectric conversion efficiency of materials, the thermal conduction needs to be suppressed, and the lattice dynamics and the thermal transport mechanisms must be better understood. Lattice thermal conduction of conventional solids is dominated by phonon propagation; however, diffuson-like thermal transport can become predominant in materials with ultralow thermal conductivity. New strategies for a simultaneous suppression of both propagative and diffusive thermal transports will be discussed in this talk based on state-of-the-art theories. Zintl compounds were recently found to exhibit exceptional thermoelectric properties. A thorough experimental study of the thermoelectric transport and carrier properties of Zintl compounds will be discussed. It will be shown that a high figure of merit over a broad temperature range can be realized through the suppression of the intrinsic carrier excitation.

November 28, 2024 (Thursday) 4:30-5:30pm
Structural colors use nanostructured building blocks or thin films to resonantly reflect or scatter light to generate colors and can exhibit higher resolution, saturation, and durability than pigment-based colors. To create structural color based paintings, it is essential to develop a capability of spatially varying the dimensions of these nanosized structures. Recently we reported a high-throughput and wafer-scale nanopatterning method by combining interference lithography and grayscale-patterned secondary exposure (IL-GPSE) to spatially modulate nanostructure feature sizes on large scale while maintaining sufficiently high resolution. Here, we employ the IL-GPSE method in the fabrication of wafer-scale structural color paintings, which can improve the patterning efficiency by orders of magnitude when compared with e-beam lithography. The fabrication techniques developed in this work have unique potentials for broader applications in biomedical sensing, spectral filtering, anti-counterfeiting or encryption, etc.

January 9, 2024 (Thursday) 2:30-3:30pm
We demonstrate that grain boundaries (GBs) behave as Brownian ratchets, exhibiting direction-dependent mobilities and unidirectional motion under oscillatory driving forces or cyclic thermal annealing. We observed these phenomena for nearly all nonsymmetric GBs but not for symmetric ones. Our observations build on molecular dynamics and phase-field crystal simulations for a wide range of GB types and driving forces in both bicrystal and polycrystalline microstructures. We corroborate these simulation results through in situ experimental observations. We analyze these results with a Markov chain model and explore the implications of GB ratchet behavior for materials processing and microstructure tailoring.

May 16, 2024 (Thursday) 4:30-5:30pm
In the era of the Internet of Things, portable electronic technology can help citizens to avail advanced features and characteristics in different facets of their daily life. These electronics powered by energy storage devices need regular recharging, but the increasing demand for continuous operation is driving research into new power supplies that can deliver stable electricity. One major development has been a conceptual shift away from grid supply charging toward self-charging. Triboelectric nanogenerators (TENGs) are emerging as a power supply for self-charged electronics due to their lightweight, simple fabrication, diversity in material selection, and high energy conversion efficiency, but the power output of TENGs needs to be trimmed to stably power the electronics. In this talk, I will address several strategies for power management of TENGs to achieve high-performing self-chargeable electronics, including current output boosting, ion-assisted contact electrification, and energy storage control.