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Controlling the shape of 3D microstructures by temperature and light
摘要： Stimuli-responsive microstructures are critical to create adaptable systems in soft robotics and biosciences. For such applications, the materials must be compatible with aqueous environments and enable the manufacturing of three-dimensional structures. Poly(N-isopropylacrylamide) (pNIPAM) is a well-established polymer, exhibiting a substantial response to changes in temperature close to its lower critical solution temperature. To create complex actuation patterns, materials that react differently with respect to a stimulus are required. Here, we introduce functional three-dimensional hetero-microstructures based on pNIPAM. By variation of the local exposure dose in three-dimensional laser lithography, we demonstrate that the material parameters can be altered on demand in a single resist formulation. We explore this concept for sophisticated three-dimensional architectures with large-amplitude and complex responses. The experimental results are consistent with numerical calculations, able to predict the actuation response. Furthermore, a spatially controlled response is achieved by inducing a local temperature increase by two-photon absorption of focused light.
关键词： light-induced actuation,pNIPAM,temperature response,stimuli-responsive materials,gray-tone lithography,hetero-microstructures,laser lithography,3D microstructures
更新于2025-09-23 15:22:29
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Stimuli‐Responsive Luminescent Copper Nanoclusters in Alginate and Their Sensing Ability for Glucose
摘要： Visually observable pH-responsive luminescent materials are developed through integrating the properties of aggregation-induced emission enhancement of Cu nanocluster (NCs) and the Ca2+ triggered gelatin of alginate. Sodium alginate, CaCO3 nanoparticles and Cu NCs are dispersed in aqueous solution, which is in a transparent fluid state, showing a weak photoluminescence (PL). The introduced H+ can react with the CaCO3 nanoparticles to produce free Ca2+, which can cross-link the alginate chains into gel networks. Meanwhile, a dramatically increase on the PL intensity of Cu NCs and a blue shift on the PL peak appeared, assigned to the Ca2+ induced enhancement and gelatin induced enhancement, respectively. Their potential application as a sensor for glucose is also demonstrated based on the principle that glucose oxidase can recognize glucose and produce H+, which further triggers the above mentioned two-stage enhancement. A linear relationship between the PL intensity and concentration of glucose in the range of 0.1 to 2.0 mM is obtained, with a limit of detection calculated as 3.2×10-5 M.
关键词： alginate,stimuli‐responsive materials,aggregation-induced emission,photoluminescence,metal nanoclusters,glucose
更新于2025-09-19 17:15:36
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Phase behavior of main-chain liquid crystalline polymer networks synthesized by alkyne–azide cycloaddition chemistry
摘要： Liquid crystalline polymer networks (LCNs) couple polymer chain organization to molecular ordering, the switching of which has been shown to impart stimuli-responsive properties, including actuation and one-way shape memory, to the networks. While LCNs have long been proposed as artificial muscles, recent reports have also suggested potential as dynamic biomaterial substrates. In contrast to many existing LCNs synthesized using hydrophobic spacers, this work investigates networks synthesized using more hydrophilic spacers to promote interaction with water. A challenge with such materials is liquid crystalline phases could be disrupted in hydrated networks. This work thus investigates the impact of polyether spacers and mesogen composition on the phase behavior of LCNs. Main-chain LCNs were synthesized using alkyne–azide cycloaddition ("click" chemistry), where two different mesogens (5yH and 5yMe) and a non-LC monomer (5yTe) were coupled with one of two different polyether spacers, poly(ethylene glycol) and poly(propylene glycol), and a crosslinker. The chemistry led to high gel fraction materials, the workup of which resulted in networks that displayed no difference in cellular toxicity due to leachable components compared to tissue culture plastic control. Calorimetric analysis, dynamic mechanical analysis, and X-ray scattering revealed the LC microstructure and temperature-responsive properties of the networks. The use of low molecular weight polyether spacers was found to prevent their crystallization within the LC network, and adjusting mesogen composition to enhance its LC phase stability allowed the use of spacers with larger molecular weights and pendant groups. Hydrated networks were found to rearrange their structure compared to dry networks, while maintaining their LC phases. Like other crosslinked LC materials, the networks display shape changes (actuation) that are tied to changes in LC ordering. The result is a new synthetic approach for polydomain networks that form stable LC phases that are tailorable using polyether spacers and may enable future application as hydrated, stimuli-responsive materials.
关键词： Liquid crystalline polymer networks,Phase behavior,Alkyne–azide cycloaddition,Stimuli-responsive materials,Polyether spacers
更新于2025-09-04 15:30:14