Ionic liquid (IL)-based drug delivery systems have attracted considerable interest owing to their intrinsic tunability and ability to transport small or large molecules through the skin. However, the development of "green" ILs remains challenging. Herein, eight potentially "green" fatty acid-based amino acid ILs (FAAAE-ILs) were synthesized, and their potency in transdermal drug delivery was investigated using ibuprofen and a peptide drug. The synthesized ILs were characterized to evaluate their physicochemical, thermal, and biological (cytotoxicity) properties. The in vitro skin permeability of the synthesized FAAAE-ILs was evaluated through pig skin. All of the FAAAE-ILs are liquid at room temperature and freely miscible with pharmaceuticals-permitted solvents/agents (e.g., isopropyl myristate (IPM), Span-20, and DMSO). In vitro cytotoxicity study showed that the cell viability of all FAAAE-ILs (10% in IPM) was at least 10 times lower than that for a conventional chemical permeation enhancer (CPE), sodium lauryl sulfate. FAAAE-ILs facilitated excellent ibuprofen solubility through multiple hydrogen bonding interactions between the drug and the ILs. An in vitro permeation study showed that the FAAAE-ILs were more effective in enhancing the permeability of drug molecules than the conventional CPE transcutol. The linoleate-based ILs showed a higher degree of permeation than the oleatebased ILs. Among the linoleate-based ILs and ibuprofen formulations (drug in 10% IL in IPM), the L-proline ethyl ester linoleate ([L-ProEt][Lin])-based formulation exhibited best results, followed by β-alanine ethyl ester linoleate, D-proline ethyl ester linoleate, and L-leucine ethyl ester linoleate after 48 h. Interestingly, the same FAAAE-IL ([L-ProEt][Lin])-containing formulation showed significant enhancement of peptide penetration across pig skin compared with CPE-containing formulations (10% in IPM). The results demonstrate that the FAAAE-IL is a promising green alternative to conventional CPEs for the transdermal delivery of small and large therapeutic molecules.

Mechanically responsive crystals have been increasingly explored, mainly based on photoisomerization. However, photoisomerization has some disadvantages for crystal actuation, such as a slow actuation speed, no actuation of thick crystals, and a narrow wavelength range. Here we report photothermally driven fast-bending actuation and simulation of a salicylideneaniline derivative crystal with an o-amino substituent in enol form. Under ultraviolet (UV) light irradiation, these thin (<20 μm) crystals bent but the thick (>40 μm) crystals did not due to photoisomerization; in contrast, thick crystals bent very quickly (in several milliseconds) due to the photothermal effect, even by visible light. Finally, 500 Hz high-frequency bending was achieved by pulsed UV laser irradiation. The generated photothermal energy was estimated based on the photodynamics using femtosecond transient absorption. Photothermal bending is caused by a nonsteady temperature gradient in the thickness direction due to the heat conduction of photothermal energy generated near the crystal surface. The temperature gradient was calculated based on the one-dimensional nonsteady heat conduction equation to simulate photothermally driven crystal bending successfully. Most crystals that absorb light have their own photothermal effects. It is expected that the creation and design of actuation of almost all crystals will be possible via the photothermal effect, which cannot be realized by photoisomerization, and the potential and versatility of crystals as actuation materials will expand in the near future.

The thermal properties of novel nanomaterials play a significant role in determining the performance of the material in technological applications. Herein, direct measurement of the temperature diffusivity of nanocellulose-doped starch–polyurethane nanocomposite films was carried out by the micro-contact method. Polymer films containing up to 2 wt%. of nanocellulose were synthesised by a simple chemical process and are biodegradable. Films of a high optical transmittance T≈80% (for a 200 μm thick film), which were up to 44% crystalline, were characterised. Two different modalities of temperature diffusivity based on (1) a resistance change and (2) micro-thermocouple detected voltage modulation caused by the heat wave, were used for the polymer films with cross sections of ∼100 μm thickness. Twice different in-plane α‖ and out-of-plane α⊥ temperature diffusivities were directly determined with high fidelity: α‖=2.12×10−7 m2/s and α⊥=1.13×10−7 m2/s. This work provides an example of a direct contact measurement of thermal properties of nanocellulose composite biodegradable polymer films. The thermal diffusivity, which is usually high in strongly interconnected networks and crystals, was investigated for the first time in this polymer nanocomposite.

The flourishing field of soft robotics requires versatile actuation methodology. Natural vibration is a physical phenomenon that can occur in any material. Here, we report high-speed bending of anisole crystals by natural vibration induced by the photothermal effect. Rod-shaped crystal cantilevers undergo small, fast repetitive bending (~0.2°) due to natural vibration accompanied by large photothermal bending (~1°) under ultraviolet light irradiation. The natural vibration is greatly amplified by resonance upon pulsed light irradiation at the natural frequency to realise high frequency (~700 Hz), large bending (~4°), and high energy conversion efficiency from light to mechanical energy. The natural vibration is induced by the thermal load generated by the temperature gradient in the crystal due to the photothermal effect. The bending behaviour is successfully simulated using finite element analysis. Any light-absorbing crystal can be actuated by photothermally induced natural vibration. This finding of versatile crystal actuation can lead to the development of soft robots with high-speed and high-efficient actuation capabilities.

The multiply oxygenated ABC-ring system of the dihydro-β-agarofurans was synthesized by employing two highly stereoselective reactions. The quinidine-catalyzed Diels-Alder reaction between a chiral dienophile and 3-hydroxy-4-methyl-2-pyrone simultaneously installed the C2-stereogenic center and two contiguous tetrasubstituted carbon centers (C5 and C10) of the A-ring. After 12 additional transformations, the aldol reaction of the resulting spiral AC-ring cyclized the B-ring with stereoselective introduction of the C7- and C8-centers.