arXiv subjects

Xiuyang Xia

Publications and source records attributed to Xiuyang Xia.

9 recordsLinked to original sources

arXiv2026

Superselectivity as a Receptor-Fluctuation Response

Superselective multivalent binding enables sharp receptor-density discrimination in targeting and sensing, but what its logarithmic response measures microscopically remains unclear. Here, we derive an exact response decomposition of the selectivity into receptor-state reweighting and a direct occupation response. In the dilute quenched Poisson limit, the direct term vanishes and selectivity is exactly the mean receptor excess beneath bound particles, which can be measured at a single density from a sufficiently large co-registered receptor-particle image. Beyond Poisson statistics, the excess is normalized by the Fano factor for a linear count response, while changes in distribution shape require the full count-resolved response. Lattice simulations verify these relations across distinct receptor statistics, while off-lattice simulations show that particle crowding enters through the direct term. These results establish a fluctuation-response framework linking multivalent selectivity to the local receptor fluctuations preferentially sampled by adsorption.

cond-mat.soft↗

arXiv2026

Entropy-driven physical amplification in multivalent biosensing

Sensitive detection of low-abundance molecular targets is widely assumed to require enzymatic amplification, such as PCR, to achieve low detection limits. In amplification-free platforms, sensitivity is traditionally constrained by equilibrium binding affinity. Here we show that multivalent linker entropy provides a distinct physical route to exponential sensitivity enhancement in purely equilibrium sensing architectures. Using a statistical-mechanical theory supported by grand canonical Monte Carlo simulations, we demonstrate that redistributing a fixed total interaction strength over increasing linker valency exponentially lowers adsorption thresholds. This scaling emerges not from stronger energetic affinity, but from the rapid growth of combinatorial binding configurations, revealing entropy as an intrinsic amplification mechanism. Consequently, detection limits can be tuned independently of bond strength, enabling ultrasensitive responses without enzymatic replication. Our results establish a general physical design principle for engineering amplification-free detection systems capable of approaching PCR-level sensitivities through entropy-driven collective effects.

cond-mat.soft↗

arXiv2025

Designed self-assembly of programmable colloidal atom-electron equivalents

To unlock the potential for assembling complex colloidal "molecules", we investigate a minimal binary system of programmable colloidal atom-electron equivalents (PAE-EE), where electron equivalents (EEs) are multivalent linkers with two distinct types of single-stranded DNA (ssDNA) ends complementary to those ssDNAs on binary programmable atom equivalents (PAEs). We derive a statistical mechanical framework for calculating the effective interaction between PAEs mediated by EEs with arbitrary valency, which quantitatively agrees with simulations that explicitly include EEs. Our analysis reveals an anomalous dependence of PAE-PAE interactions on the EE valency, showing that EE-mediated interactions converge at the large valency limit. Moreover, we identify an optimal EE valency that maximizes the interaction difference between targeted and non-targeted binding pairs of PAEs. These findings offer design principles for targeted self-assembly in PAE-EE systems.

cond-mat.soft↗

arXiv2024

Designing superselectivity in linker-mediated multivalent nanoparticle adsorption

Using a statistical mechanical model and numerical simulations, we provide the design principle for the bridging strength ($ξ$) and linker density ($ρ$) dependent superselectivity in linker-mediated multivalent nanoparticle adsorption. When the bridges are insufficient, the formation of multiple bridges leads to both $ξ$- and $ρ$-dependent superselectivity. Whereas, when the bridges are excessive, the system becomes insensitive to bridging strength due to entropy-induced self-saturation and shows a superselective desorption with respect to the linker density. Counterintuitively, lower linker density or stronger bridging strength enhances the superselectivity. These findings enhance understanding of relevant biological processes and open up opportunities for applications in biosensing, drug delivery, and programmable self-assembly.

cond-mat.soft↗

arXiv2024

A bond swap algorithm for simulating dynamically crosslinked polymers

Materials incorporating covalent adaptive networks (CAN), e.g., vitrimers, have received significant scientific attention due to their distinctive attributes of self-healing and stimuli-responsive properties. Different from direct crosslinked systems, bivalent and multivalent systems require a bond swap algorithm that respects detailed balance, considering the multiple equilibria in the system. Here we propose a simple and robust algorithm to handle bond swap in multivalent and multi-species CAN systems. By including a bias term in the acceptance of Monte Carlo moves, we eliminate the imbalance from the bond swap site selection and multivalency effects, ensuring the detailed balance for all species in the system.

cond-mat.soft↗

arXiv2023

The role of receptor uniformity in multivalent binding

Multivalency is prevalent in various biological systems and applications due to the superselectivity that arises from the cooperativity of multivalent binding. Traditionally, it was thought that weaker individual binding would improve the selectivity in multivalent targeting. Here using analytical mean field theory and Monte Carlo simulations, we discover that for receptors that are highly uniformly distributed, the highest selectivity occurs at an intermediate binding energy and can be significantly greater than the weak binding limit. This is caused by an exponential relationship between the bound fraction and receptor concentration, which is influenced by both the strength and combinatorial entropy of binding. Our findings not only provide new guidelines for the rational design of biosensors using multivalent nano-particles but also introduce a new perspective in understanding biological processes involving multivalency.

cond-mat.soft↗

arXiv2022

Entropy driven thermo-gelling vitrimer

Thermo-gelling polymers have been envisioned as promising smart biomaterials but limited to their weak mechanical and thermodynamic stabilities. Here we propose a new thermo-gelling vitrimer, which remains at a liquid state because of the addition of protector molecules preventing the crosslinking, and with increasing temperature, an entropy driven crosslinking occurs to induce the sol-gel transition. Moreover, we find that the activation barrier in the metathesis reaction of vitrimers plays an important role, and experimentally one can use catalysts to tune the activation barrier to drive the vitrimer to form an equilibrium gel at high temperature, which is not subject to any thermodynamic instability. We formulate a mean field theory to describe the entropy driven crosslinking of the vitrimer, which agrees quantitatively with computer simulations, and paves the way for design and fabrication of novel vitrimers for biomedical applications.

cond-mat.soft↗

arXiv2020

Entropy-Controlled Cross-Linking in Linker-Mediated Vitrimers

Recently developed linker-mediated vitrimers based on metathesis of dioxaborolanes with various commercially available polymers have shown both good processability and outstanding performance, such as mechanical, thermal, and chemical resistance, suggesting new ways of processing cross-linked polymers in industry, of which the design principle remains unknown [M. Rottger, et al., Science 356, 62 (2017)]. Here we formulate a theoretical framework to elucidate the phase behaviour of the linker-mediated vitrimers, in which entropy plays a governing role. We find that with increasing the linker concentration, vitrimers undergo a reentrant gel-sol transition, which explains a recent experiment [S. Wu, H. Yang, S. Huang, Q. Chen, Macromolecules 53, 1180 (2020)]. More intriguingly, at the low temperature limit, the linker concentration still determines the cross-linking degree of the vitrimers, which originates from the competition between the conformational entropy of polymers and the translational entropy of linkers. Our theoretical predictions agree quantitatively with computer simulations, and offer guidelines in understanding and controlling the properties of this newly developed vitrimer system.

cond-mat.soft↗

arXiv2020

Linker-mediated self-assembly of mobile DNA-coated colloids

Developing construction methods of materials tailored for given applications with absolute control over building block placement poses an immense challenge. DNA-coated colloids offer the possibility of realising programmable self-assembly, which, in principle, can assemble almost any structure in equilibrium, but remains challenging experimentally. Here, we propose an innovative system of linker-mediated mobile DNA-coated colloids (mDNACCs), in which mDNACCs are bridged by the free DNA linkers in solution, whose two single-stranded DNA tails can bind with specific single-stranded DNA receptors of complementary sequence coated on colloids. We formulate a mean-field theory efficiently calculating the effective interaction between mDNACCs, where the entropy of DNA linkers plays a nontrivial role. Particularly, when the binding between free DNA linkers in solution and the corresponding receptors on mDNACCs is strong, the linker-mediated colloidal interaction is determined by the linker entropy depending on the linker concentration.

cond-mat.soft↗