About

Ruobing Bai is an assistant professor in the Department of Mechanical and Industrial Engineering at Northeastern University. His research combines theory and experiment in solid mechanics, materials science, and other multiphysical processes. His areas of focus include multifunctional materials, fracture, adhesion, strengthening and toughening, sustainable materials, soft robotics, human-machine interfaces, and energy storage systems. Bai has a strong background in theoretical modeling and utilizes modern laboratory facilities for material synthesis, fabrication, and characterization. He completed his bachelor’s degree at Peking University, his PhD at Harvard University, and a postdoctoral training at the California Institute of Technology, all in solid mechanics. Bai has received numerous awards, including the NSF CAREER Award, ACS Petroleum Research Fund Doctoral New Investigator Award, EML Young Investigator Award, and the ASME Haythornthwaite Research Initiation Award. He is actively involved in professional service, serving on the Extreme Mechanics Letters Early Career Advisory Board and as the secretary of the ASME 'Mechanics of Soft Materials' technical committee. His research aims to advance durable, intelligent, and sustainable mechanical systems through innovative materials and mechanisms.

Research topics

• Computer Science
• Chemistry
• Organic chemistry
• Materials science
• Engineering
• Chemical engineering
• Process engineering

Selected publications

• Thermoviscoelasticity of polydomain liquid crystal elastomers regulated by soft elasticity

  ArXiv.org · 2026-05-12

  articleOpen accessSenior author

  Liquid crystal elastomers (LCEs) are elastomeric networks with rod-like mesogens that reorient under load. In polydomain LCEs, this reorientation drives a polydomain-to-monodomain transition that produces a soft-elastic plateau. Coupling between this soft elasticity and polymer-network viscoelasticity yields a path-dependent thermoviscoelastic response, central to applications in damping, impact protection, and tough adhesives. However, the physics governing this response under complex thermomechanical histories remains insufficiently studied. We present a combined experimental and theoretical study of polydomain LCEs under three uniaxial protocols: single-cycle loading-unloading, stress-free recovery from various pre-stretches, and multi-cycle loading with progressively increasing amplitude. We develop a finite-deformation constitutive model combining two parallel mechanisms: rate-independent, temperature-dependent soft elasticity from mesogen reorientation, and time- and temperature-dependent viscoelasticity. With a single parameter set, the model quantitatively reproduces all three protocols and resolves each mechanism's contribution. A temperature-dependent soft-elastic limit governs the low-rate response and the long-time recovered stretch, while viscoelasticity controls the rate-dependent deviation and the cycle-wise accumulation of residual stretch away from this limit. A thermal recovery test above the nematic-isotropic transition confirms that all hysteresis and residual deformation are reversible, ruling out irreversible damage. The framework provides mechanistic understanding and a predictive basis for designing polydomain LCE components under complex thermomechanical histories.

  PublisherOA PDF

• Anomalous thermomechanical actuation of liquid crystal elastomer balloons

  Extreme Mechanics Letters · 2026-01-14 · 1 citations

  articleSenior author
  PublisherDOI

• Influence of water-soaking on the mechanical properties of liquid crystal elastomers: an experimental study

  Acta Mechanica Sinica · 2026-05-21

  article
  PublisherDOI

• Thermoviscoelasticity of polydomain liquid crystal elastomers regulated by soft elasticity

  arXiv (Cornell University) · 2026-05-12

  preprintOpen accessSenior author

  Liquid crystal elastomers (LCEs) are elastomeric networks with rod-like mesogens that reorient under load. In polydomain LCEs, this reorientation drives a polydomain-to-monodomain transition that produces a soft-elastic plateau. Coupling between this soft elasticity and polymer-network viscoelasticity yields a path-dependent thermoviscoelastic response, central to applications in damping, impact protection, and tough adhesives. However, the physics governing this response under complex thermomechanical histories remains insufficiently studied. We present a combined experimental and theoretical study of polydomain LCEs under three uniaxial protocols: single-cycle loading-unloading, stress-free recovery from various pre-stretches, and multi-cycle loading with progressively increasing amplitude. We develop a finite-deformation constitutive model combining two parallel mechanisms: rate-independent, temperature-dependent soft elasticity from mesogen reorientation, and time- and temperature-dependent viscoelasticity. With a single parameter set, the model quantitatively reproduces all three protocols and resolves each mechanism's contribution. A temperature-dependent soft-elastic limit governs the low-rate response and the long-time recovered stretch, while viscoelasticity controls the rate-dependent deviation and the cycle-wise accumulation of residual stretch away from this limit. A thermal recovery test above the nematic-isotropic transition confirms that all hysteresis and residual deformation are reversible, ruling out irreversible damage. The framework provides mechanistic understanding and a predictive basis for designing polydomain LCE components under complex thermomechanical histories.

  PublisherDOI

• Nanoplastics trigger glial–neuronal collagen signaling miscommunication to exacerbate cognitive impairment in Alzheimer's disease

  Alzheimer s & Dementia · 2026-01-01

  articleOpen access

  INTRODUCTION: Alzheimer's disease (AD) is a progressive neurodegenerative disorder with limited treatments and poorly defined environmental risks. Micro- and nanoplastics (MNPs) are widespread pollutants linked to neurotoxicity, but their role in AD remains unclear. METHODS: We investigated the effects of 90-day intragastric exposure to polystyrene nanoplastics (PS-NPs) in amyloid precursor protein/presenilin 1 (APP/PS1) mice using behavioral tests, brain imaging, histopathology, and cell-type-resolved proteomics. RESULTS: PS-NPs exacerbated cognitive deficits and hippocampal damage in APP/PS1 mice. Proteomic and CellChat analyses revealed PS-NPs enhanced neuroglial communication through the collagen-integrin axis. In vitro triculture demonstrated that PS-NPs strengthened collagen-mediated astrocyte-microglia-neuron signaling, whereas in vivo blockade with TC-I 15 suppressed collagen activation and improved cognition in PS-NP-exposed APP/PS1 mice. Single-nucleus RNA sequencing of human AD brains validated conserved activation of collagen signaling. DISCUSSION: Our findings highlight that PS-NPs exacerbate cognitive impairment in AD by driving collagen-dependent neuroglial dysfunction, establishing MNPs as modifiable environmental risk factors. HIGHLIGHTS: MNPs act as environmental risk factors that worsen cognitive impairment in AD. PS-NPs trigger glial-neuronal communication via the collagen-integrin axis in AD. PS-NP-induced astrocyte- and microglia-derived collagen, driving neurotoxicity in AD. TC-I 15 blocked collagen signaling and rescued cognition in PS-NP-exposed AD mice. Collagen signaling was upregulated in human AD brains, confirming disease relevance.

  PublisherOA PDFDOI

• Ethylene Pretreatment Enhances Ethylene Adsorption and Separation over Cu@SAPO‐RHO Zeolite

  Angewandte Chemie International Edition · 2025-03-22 · 23 citations

  articleOpen access1st author

  Abstract Efficient ethylene/ethane (C 2 H 4 /C 2 H 6 ) separation using low‐energy technologies is crucial for the chemical industry yet remains challenging due to the lack of industrially applicable adsorbents. Cu(I)‐based adsorbents show significant potential; however, traditional synthesis methods often involve complex procedures or reduction steps. Herein, we report that Cu@SAPO‐RHO zeolite, synthesized for the first time via a one‐pot method with cyclam as the Cu(II) ligand, exhibits a remarkable C 2 H 4 /C 2 H 6 selectivity of 22.6, a C 2 H 4 uptake of 3.08 mmol g −1 , and a separation factor of 9.4 under ambient conditions by using a C 2 H 4 pretreatment, placing it among the best‐performing zeolitic materials. The C 2 H 4 pretreatment enhances separation efficiency by partially reducing Cu(II) to Cu(I) and water resistance through the formation of carbon species during pretreatment. Structural analysis using Rietveld refinement reveals that Cu 2+ ions occupy the corners of elliptical single 8‐rings ( s 8 r ). X‐ray absorption near‐edge structure analysis confirms a reduction in the Cu oxidation state, while X‐ray photoelectron spectroscopy corroborates the partial conversion of Cu(II) to Cu(I). Periodic density functional theory calculations further reveal that Cu(I) interacts more strongly with C 2 H 4 than Cu(II). With its straightforward synthesis and enhanced performance through C 2 H 4 pretreatment, Cu@SAPO‐RHO zeolite presents a promising solution for industrial‐scale C 2 H 4 /C 2 H 6 separation.

  PublisherOA PDFDOI

• Multiparametric 3D-MRE for Longitudinal Monitoring of Disease Progression in CHB Patients, With or Without Treatment

  Proceedings on CD-ROM - International Society for Magnetic Resonance in Medicine. Scientific Meeting and Exhibition/Proceedings of the International Society for Magnetic Resonance in Medicine, Scientific Meeting and Exhibition · 2025-09-16

  article

  Motivation: Three-dimensional magnetic resonance elastography (3D-MRE) can detect necroinflammation and fibrosis in chronic hepatitis B (CHB) patients. However, few studies have examined the ability of 3D-MRE to monitor liver changes in CHB patients, both with and without antiviral treatment. Goal(s): To develop a non-invasive follow-up method using 3D-MRE for both treated and untreated CHB patients. Approach: Cohen's Kappa test compared the agreement between disease progression diagnosed by pathology or clinical criteria and that diagnosed by MRE. Spearman correlation analysis was performed between changes in 3D-MRE and liver histology or clinical indicators during follow-up. Results: 3D-MRE effectively monitors disease progression in CHB patients during follow-up. Impact: 3D-MRE offers a non-invasive biomarker for longitudinal monitoring in CHB patients.

  PublisherDOI

• Aged polylactic acid microplastics exacerbate lipid metabolism disorders and cardiac dysfunction via PPARγ activation in zebrafish: A comparative study with polymers and oligomers

  Ecotoxicology and Environmental Safety · 2025-11-01

  articleOpen access

  Polylactic acid (PLA), a biodegradable plastic, is increasingly promoted as a sustainable alternative to conventional plastics. However, its degradation under non-composting conditions and associated toxicological impacts remain insufficiently understood. This study aimed to compare the toxicity of PLA microplastics (MPs) at different degradation stages, including PLA polymers, oligomers, and aged polymers, in zebrafish larvae. Zebrafish were exposed to environmentally relevant concentrations (0.1, 1, and 10 mg/L), and morphological, biochemical, and transcriptomic analyses were performed. PLA MPs disrupted lipid metabolism, decreased ATP levels, and elevated reactive oxygen species production, ultimately leading to cardiac malformations. Mechanistically, PLA MPs activated the peroxisome proliferator-activated receptor γ (PPARγ), upregulating genes related to lipid storage and cardiac development. Co-exposure with a PPARγ antagonist GW9662 partially alleviated these effects, confirming the role of PPARγ-mediated pathways in PLA MP-induced lipid disruption and cardiotoxicity. Notably, PLA polymers showing stronger cardiac dysfunction than PLA oligomers and ultraviolet (UV)-aged PLA polymers. These findings provided critical evidence that PLA MPs impair energy homeostasis and cardiac development in zebrafish, underscoring the urgent need for comprehensive ecological risk assessments of PLA-based materials under realistic environmental conditions. • PLA MPs disrupt lipid metabolism and cardiotoxicity via PPARγ activation. • Polymers cause stronger cardiac dysfunction than UV-aged polymers and oligomers. • PPARγ antagonist GW9662 mitigates PLA-induced cardiac and metabolic defects. • Environmental aging amplifies PLA toxicity, challenging its "green" label.

  PublisherDOI

• Polystyrene nanoplastics trigger ferroptosis in Nrf2-deficient gut via ether phospholipid accumulation

  Environment International · 2025-03-01 · 14 citations

  articleOpen access

  • PS-NPs induce intestinal epithelial cells ferroptosis, in a form of lipid peroxidation-driven cell death. • Nrf2 plays a crucial protective role in preventing ferroptosis by regulating lipid metabolism and counteracting lipid peroxidation. • PS-NP exposure disrupt ether phospholipid metabolism, leading to heightened lipid peroxidation in the intestines of Nrf2 fl/fl -Vil Cre+ mice. • In high-fat diet, individuals with reduced NRF2 activity may be vulnerable to PS-NP-induced intestinal damage. The widespread environmental presence of nanoplastics (NPs) raises significant concerns about their health impacts, particularly on the gastrointestinal system, as NPs are primarily ingested. While previous studies have linked NP-induced intestinal toxicity to oxidative stress and reactive oxygen species (ROS) accumulation, the specific mechanisms of cell death remain unclear. Here, we showed that environmentally relevant concentrations of polystyrene nanoplastics (PS-NPs) induced ferroptosis, a form of lipid peroxidation-driven cell death, in intestinal epithelial cells. Using intestinal epithelial-specific Nrf2 -deficient mice ( Nrf2 fl/fl -Vil Cre+ ) and human intestinal epithelial Caco-2 cells, we demonstrated that Nrf2 , a key oxidative stress regulator, play a protective role against PS-NP-induced ferroptosis. PS-NP exposure disrupted ether phospholipid metabolism, leading to the accumulation of polyunsaturated fatty acid-ether phospholipids and heightened lipid peroxidation in the intestines of Nrf2 fl/fl -Vil Cre+ mice. This accumulation increased the susceptibility of intestinal epithelial cells to ferroptosis. Additionally, a high-fat diet further exacerbated this effect, suggesting that individuals with reduced NRF2 activity and poor dietary habits may be especially vulnerable to PS-NP-induced intestinal damage. Our findings offered new insights into the molecular mechanisms of NP-induced intestinal toxicity and underscored the health risks posed by environmental PS-NP exposure, particularly in populations with compromised antioxidant defenses.

  PublisherDOI

• Highly switchable and reversible soft sticky adhesives based on thermo-responsive phase separation

  Extreme Mechanics Letters · 2025-01-25 · 4 citations

  articleOpen accessSenior authorCorresponding

  Many biological systems can switch between strong adhering and non-adhering states to various materials with complex shapes and sizes in a reversible manner. By contrast, synthetic soft sticky adhesives, or pressure-sensitive adhesives, still face challenges in combining high switchability, reversible switching, facile switching operation, and applicability to diverse materials, shapes, and sizes. To address this challenge, here we present a highly switchable and reversible soft sticky adhesive based on thermal-induced phase separation in a thermo-responsive hydrogel. At room temperature, the hydrogel adhesive is toughened by nanoclay as noncovalent crosslinkers, showing an adhesion strength of 60–80 kPa to various adherends. This adhesion is almost completely switched off upon heating, with a residual strength of around 1 kPa. The switching is reversible for many cycles, enabling selective pick-and-release of objects with various materials, shapes, sizes, and weights. The switching time is around 10 s with an adhesive layer of 1 mm, governed by thermal conduction through the adhesive, faster than or comparable to most state-of-the-art methods. The adhesive is self-healing, and can be recycled, dried, stored, reswollen, and reused with nearly intact adhesion and switching properties. These features are hoped to advance technologies such as on-demand device disassembly for recycling, assembly-based manufacturing, biomimetic robots, and human-machine interfaces.

  PublisherDOI

Recent grants

• Mesoscale Photomechanical Coupling in Photoactive Liquid Crystal Elastomers

  NSF · $339k · 2022–2025

Frequent coauthors

• Zhigang Suo

  Harvard University

  27 shared

• Zhenlie Huang

  Southern Medical University

  20 shared

• Yuji Huang

  Southern Medical University

  17 shared

• Yizhou Zhong

  Southern Medical University

  17 shared

• Boxuan Liang

  Southern Medical University

  16 shared

• Rongyi Ye

  Southern Medical University

  16 shared

• Xavier Morelle

  Université Claude Bernard Lyon 1

  16 shared

• Jihong Yu

  Jilin University

  15 shared

Labs

• Bai Research GroupPI

Education

• PhD

  Harvard University

  2018

Awards & honors

• NSF CAREER Award
• ACS Petroleum Research Fund Doctoral New Investigator Award
• EML Young Investigator Award
• ASME Haythornthwaite Research Initiation Award
• JMPS Best Referee Award