Effects of geometry and composition of soft polymer films embedded with nanoparticles on rates for optothermal heat dissipation

Abstract

Embedding soft matter with nanoparticles (NPs) can provide electromagnetic tunability at sub-micron scales for a growing number of applications in healthcare, sustainable energy, and chemical processing. However, the use of NP-embedded soft material in temperature-sensitive applications has been constrained by difficulties in validating the prediction of rates for energy dissipation from thermally insulating to conducting behavior. This work improved the embedment of monodisperse NPs to stably decrease the inter-NP spacings in polydimethylsiloxane (PDMS) to nano-scale distances. Lumped-parameter and finite element analyses were refined to apportion the effects of the structure and composition of the NP-embedded soft polymer on the rates for conductive, convective, and radiative heat dissipation. These advances allowed for the rational selection of PDMS size and NP composition to optimize measured rates of internal (conductive) and external (convective and radiative) heat dissipation. Stably reducing the distance between monodisperse NPs to nano-scale intervals increased the overall heat dissipation rate by up to 29%. Refined fabrication of NP-embedded polymer enabled the tunability of the dynamic thermal response (the ratio of internal to external dissipation rate) by a factor of 3.1 to achieve a value of 0.091, the largest reported to date. Heat dissipation rates simulated a priori were consistent with 130 μm resolution thermal images across 2- to 15-fold changes in the geometry and composition of NP-PDMS. The Nusselt number was observed to increase with the fourth root of the Rayleigh number across thermally insulative and conductive regimes, further validating the approach. These developments support the model-informed design of soft media embedded with nano-scale-spaced NPs to optimize the heat dissipation rates for evolving temperature-sensitive diagnostic and therapeutic modalities, as well as emerging uses in flexible bioelectronics, cell and tissue culture, and solar-thermal heating.

Initial dynamic thermal dissipation modes enhance heat dissipation in gold nanoparticle–polydimethylsiloxane thin films

“…This included heat dissipation rates measured at steady state (15-45 s, blue symbols) for pixels inside (filled symbols) adjacent (half-filled symbols) and outside (open symbols) the laser spot at both 13.5 mW (circles) and 25 mW (triangles). These observed effects of film thickness reducing thermal dynamics matched previously reported results [26]. More concentrated AuNPs enhance multiexponential heat dissipation in pixels irradiated inside (orange) the laser spot, whose effect is reduced in pixels adjacent to (gray) or outside (blue) the spot.…”

“…The thin, optically transparent, thermally insulating PDMS films slowed conductive heat dissipation in proportion to thickness as calculated by the Biot ratio [26]. Figure 6 shows average heat dissipation rate, which is proportional to Thicker films with more AuNP thermally equilibrate slower inside the laser spot.…”

“…Thin PDMS films containing AuNPs were fabricated using a recent method that increased NP content and eliminated observable gas/vapor entrapment and NP aggregation [26]. Briefly, AuNP-PDMS films were fabricated as follows.…”

Photothermally Active Inorganic Nanoparticles: from Colloidal Solutions to Photothermally Active Printed Surfaces and Polymeric Nanocomposite Materials

“…Fabrication of plasmonic polymer nanocomposites (doped with silver or gold nanoparticles) and application in optical data storage, sensing, imaging, and implementation of photothermally active gels for in vivo therapy is discussed in a very recent review by Liz‐Marzán et al The authors stressed that the nanoporosity of the matrix, the overall mechanical stability and the dispersion of the nanoparticles are important parameters for achieving the best performance. We should consider that the application of soft materials doped with photothermally active nanoparticles may be limited by the difficulty in predicting the rates of energy dissipation in materials with widely different thermal conductivity . Roper et al improved the embedment of monodisperse PVP coated gold nanoparticles to stably decrease the inter‐NP spacings in PDMS to nano‐scale distances .…”

“…We should consider that the application of soft materials doped with photothermally active nanoparticles may be limited by the difficulty in predicting the rates of energy dissipation in materials with widely different thermal conductivity . Roper et al improved the embedment of monodisperse PVP coated gold nanoparticles to stably decrease the inter‐NP spacings in PDMS to nano‐scale distances . It was possible to make a rational selection of PDMS size and NP composition to optimize the measured rates of internal (conductive) and external (convective and radiative) heat dissipation.…”