Qun-Li Lei

In statistical physics, it is well established that the liquid-gas (LG) phase transition with divergent critical fluctuations belongs to the Ising universality class. Whether nonequilibrium effects can alter this universal behavior remains a fundamental open question. In this work, we theoretically prove that nonequilibrium hyperuniform (HU) fluids with additional center-of-mass conservation exhibit LG criticality different from the Ising universality class. As a specific case, we investigate a 2D HU fluid composed of active spinners, where phase separation is driven by dissipative collisions. Strikingly, at the critical point, the 2D HU fluid displays finite density fluctuations S ( q ) ∼ q η ∼ const with η = 0 , rather than the expected divergence S ( q ) ∼ q η − 2 with η = 1 / 4 as in the Ising model, while the compressibility still diverges. The critical point is thus calm yet highly susceptible, in fundamental violation of the conventional fluctuation-dissipation relation. Consistently, we observe short-range pair correlation functions coexisting with quasi-long-range response functions at the critical point. Based on a generalized model B and renormalization-group analysis, we prove that hyperuniformity reduces the upper critical dimension d c from 4 to 2. Moreover, the critical point exhibits Gaussian density fluctuations indicated by Binder cumulant, distinct from non-Gaussian critical behaviors of the mean-field Ising universality class. The system also exhibits nondivergent energy fluctuations rather than logarithmic divergence as expected in the Ising universality class at d = d c . Furthermore, the HU fluid undergoes nonconventional spinodal decomposition, where the decomposition time diverges but the characteristic length scale remains finite as the critical point is approached. The origin of the above anomalies lies in the nonequilibrium nature of the system which obeys a generalized fluctuation-dissipation relation 2 Im χ ( q , ω ) = ω C ( q , ω ) / k B T eff ( q ) with a scale-dependent effective temperature T eff ( q ) ∝ q 2 . These findings establish a striking exception to conventional paradigms of critical phenomena and illustrate how nonequilibrium forces can fundamentally reshape universality classes.

Parkinson's disease (PD) imposes a heavy burden on the aging population. Current oral levodopa (LD) treatment faces dual challenges: poor brain bioavailability due to systemic barriers and motor complications from fluctuating drug levels. While intranasal delivery offers direct brain access, bypassing the blood-brain barrier, existing formulations still struggle to maintain stable drug concentrations needed to prevent motor fluctuations. Moreover, focusing solely on dopamine supplements overlooks the underlying oxidative stress that drives disease progression. Herein, we report an intranasal conformal patch composed of silk fibroin nanofibers that achieves stable drug delivery through moisture-responsive adhesion, sustained release, and enhanced LD stability. The patch further incorporates a dual-drug strategy combining LD supplementation with reactive oxygen species scavenging to delay neurodegeneration. In vivo results demonstrate that this daily patch effectively delivers nanomedicines to the brain, reverses pathological status, and restores normal behavioral patterns in PD models. This wearable drug reservoir enables sustained therapeutic effects while addressing oxidative damage, representing a significant advancement in PD treatment.

The jamming transition is traditionally regarded as a geometric transition governed by static contact networks. Recently, dynamic phase transitions of athermal particles under periodic shear provide a new lens on this problem, leading to a conjecture that jamming transition corresponds to an absorbing-state transition within the Manna (conserved directed percolation) universality class. Here, by re-examing the biased random organization model, a minimal model for particles under periodic shearing that the conjecture bases on, we uncover several criticality anomalies at high density beyond the description of Manna universality class. In three-dimensional monodisperse systems, crystallization disrupts the absorbing transition, while in dense binary mixtures, a distinct transition from absorbing to active-glass states emerges, signifying a new universality class of dynamic phase transitions. Closer to jamming point, the quenched heterogeneity in the contact network smears the dynamic transition via Griffiths effects and drives the system toward heterogeneous directed percolation. We further proposal a field theory with fractional time dynamics that unifies these phenomena, establishing a theoretical framework linking jamming, disorder, and dynamic criticality.

Cells not only can be motile by crawling but are also capable of nonmotility active motions like periodic contraction or pulsation. In this work, based on a Voronoi cell model, we show how this nonmotility activity affects the structure, dynamic, and density fluctuations of cellular monolayers. Our model shows that random cell pulsation fluidizes solid epithelial tissues into a hyperuniform fluid state, while pulsation synchronization inhibits the fluidity and causes a reverse solidification. Our results indicate this solidification is a Berezinskii–Kosterlitz–Thouless-type transition, characterized by strong density/dynamic heterogeneity arising from the annihilation of topological defects in the pulsating phase space. The magnitude and length scale of density heterogeneity diverge with the pulsating period, resulting in an opposite giant density fluctuation or anti-hyperuniformity. We propose a fluctuating hydrodynamic theory that can unify the two opposite anomalous fluctuation phenomena. Our findings can help to understand recent experimental observations in Madin-Darby canine kidney monolayers.

Macromolecules can gain special properties by adopting knotted conformations, but engineering knotted macromolecules is a challenging task. Here, we unexpectedly find that knots can be efficiently generated in active polymer systems. When one end of an actively reptative polymer is anchored, it undergoes continual self-knotting as a result of intermittent giant conformation fluctuations and the outward reptative motion. Once a knot is formed, it migrates to the anchoring point due to a nonequilibrium ratchet effect. Moreover, when the active polymer is grafted on a passive polymer, it can function as a self-propelling soft needle to either transfer its own knots or directly braid knots on the passive polymer. We further show that these active needles can create intermolecular bridging knots between two passive polymers. Our finding highlights the nonequilibrium effects in modifying the dynamic pathways of polymer systems, which have potential applications in macromolecular topology engineering.

Continuous time crystals (CTCs) are characterized by sustained oscillations that break the time-translation symmetry. Since the ruling out of equilibrium CTCs by no-go theorems, the emergence of such dynamical phases has been observed in various driven-dissipative quantum platforms. The current understanding of CTCs is mainly based on mean-field theories, which fail to address the problem of whether the continuous time-translation symmetry can be broken in noisy, spatially extended systems absent in all-to-all couplings. Here, we propose a CTC realized in a quantum contact model through self-organized bistability. The CTCs stem from the interplay between collective dissipation induced by the first-order absorbing phase transitions and slow constant driving provided by an incoherent pump. The stability of such oscillatory phases in finite dimensions under the action of intrinsic quantum fluctuations is scrutinized by the functional renormalization group method and numerical simulations. Occurring at the edge of many-body synchronization, the CTC phase exhibits an inherent period and amplitude with a coherence time linearly diverging with system size, thus also constituting a boundary time crystal. Our results serve as a solid route towards self-protected CTCs in strongly interacting open systems. Published by the American Physical Society 2024

Colloidal particles can spontaneously self-assemble into ordered structures, which not only can manipulate the propagation of light, but also vibration or phonons. Using Monte Carlo simulation, we study the self-assembly of perfectly aligned segment rod particles with lateral flat cutting. Under the help of surface attractions, we find that particles with different cutting degree can self-assemble into different crystal phases characterized by bond coordination z that varies from 3 to 6. Importantly, we identify a transformable super-isostatic structures with pgg symmetry and redundant bonds (z=5). We find that this structure can support either the soft bulk model or soft edge model depending on its Poisson's ratio which can be tuned from positive to negative by a uniform soft deformation. Importantly, the bulk soft modes are associated with states of self-stress along the direction of zero strain during the uniform soft deformation. This self-assembled transformable super-isostatic structure may act as mechanical metamaterials with potential application in micro-mechanical engineering.

Transformable mechanical structures can switch between distinct mechanical states. Whether this kind of structure can be self-assembled from simple building blocks at microscale is a question to be answered. In this work, we propose a self-assembly strategy for these structures based on a nematic monolayer of segmented colloidal rods with lateral cutting. By using Monte Carlo simulation, we find that rods with different cutting degrees can self-assemble into different crystals characterized by bond coordination z that varies from 3 to 6. Among these, we identify a transformable superisostatic structure with pgg symmetry and redundant bonds (z = 5). We show that this structure can support either soft bulk modes or soft edge modes depending on its Poisson's ratio, which can be tuned from positive to negative through a uniform soft deformation. We also prove that the bulk soft modes are associated with states of self-stress along the direction of zero strain during uniform soft deformation. The self-assembled transformable structures may act as mechanical metamaterials with potential applications in micromechanical engineering.