Hysteresis is an
essential attribute of many solid-state devices
and biological processes, yet it is often overlooked in colloidal
and soft-matter dynamic systems. Herein, we show that gold nanoparticles
can remain dispersed or aggregated at the same temperature depending
on the trajectory of applied stimulus, featuring hysteretic behavior.
Aided by real-time analytics and fine-tuning of experimental parameters,
such as salt concentration, nanoparticle diameter, and surface potential,
we disentangled the kinetic (rate-dependent) and thermodynamic (rate-independent)
components of hysteresis in cyclic clustering of nanoparticles. The
hysteresis originates from the difference in the aggregation and disassembly
temperatures. Our findings enrich the repertoire of the experimental
framework with potential for stimuli-sensitive nanotransducers, information
storage, switchable catalysis, or autonomous chemical networks with
feedback loops.
Uniform endless fibers are ubiquitous and their applications range from functional textiles over biomedical engineering to high-performance filtering and drug delivery systems. Here, we report a new method for the direct, reproducible fabrication of uniform polymer and composite micro-/nanofibers using a microfluidic gas flow focusing nozzle (Gas Dynamic Virtual Nozzle (GDVN)) relinquishing the need for external fiber pulling mechanisms. Compared to other methods, this technique is inexpensive, user-friendly and permits precise fiber diameter control (~250 nm to ~15 µm), high production rate (m/s-range) and direct fiber deposition without clogging due to stable, gas-focused jetting. Control over shape (flat or round) and surface patterning are achieved by simply tuning the air pressure and polymer concentration. The main thinning process happens after the polymer exits the device and is, therefore, mostly independent of the nozzle’s internal geometry. Nevertheless, the lithography-based device design is versatile, allowing for precise flow-field control for operation stability as well as particle alignment control. As an example, we demonstrate the successful production of endless hematite nanocomposite fibers which highlights this technology’s exciting possibilities that can lead to the fabrication of multifunctional/stimuli-responsive fibers with thermal and electrical conductivity, magnetic properties and enhanced mechanical stability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.