We demonstrate that low-frequency ultrasonic stimulation applied directly to a hydrogel, at energy levels below the cavitation threshold, can control the release of a therapeutic molecule. The hydrogel that contained the molecules was enclosed within a hollow acoustic horn. The harmonic modes in the acoustic horn combined with the physical gel structure to induce a flashing ratchet that released all of the retained molecules in less than 90 s at an intensity of 1.5 W cm⁻² (applied energy of 135 J cm⁻², ultrasound center frequency of 27.9 ± 1.5 kHz). In contrast, ultrasound is used currently as a remote stimulus for drug-delivery systems, at energy levels above the cavitation threshold. The low-energy flashing ratchet approach that we describe is applicable to drive the diffusion of molecules in a range of gels that are ubiquitous in biomedical systems, including for example in drug delivery, molecule identification and separation systems.

我们证明了直接应用于水凝胶的低频超声刺激，在低于空化阈值的能量水平下，可以控制治疗分子的释放。含有分子的水凝胶被封闭在一个中空的声喇叭内。声号角中的谐波模式与物理凝胶结构相结合，产生一个闪光棘轮，在不到 90 秒的时间内以 1.5 W cm ^-2的强度释放所有保留的分子（施加的能量为 135 J cm ^-2，超声中心频率为 27.9 ± 1.5 kHz）。相比之下，超声波目前被用作药物输送系统的远程刺激，能量水平高于空化阈值。我们描述的低能量闪光棘轮方法适用于驱动分子在生物医学系统中普遍存在的一系列凝胶中的扩散，包括例如药物递送、分子识别和分离系统。