School of Engineering and Applied Sciences, Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
J Am Chem Soc. 2013 May 22;135(20):7744-50. doi: 10.1021/ja401960f. Epub 2013 May 8.
We present a new type of microcapsule programmed with a tunable active release mechanism. The capsules are triggered by a plasticizing stimulus that induces a phase change transition of the polymeric membrane from a solid to a fluidized form; thereafter, the cargo is actively driven out of the capsule through a defect at the capsule wall with controllable release kinetics. Tuning the degree of membrane fluidity by tailoring the amount of plasticizing stimulus present allows us to obtain temporal variation of the release kinetics from a subsecond abrupt burst release to a slow sustained release of encapsulant over many minutes. Moreover, we demonstrate tuning of the collective capsule triggering response by adjusting stimulus content, polymer molecular weight, and capsule membrane thickness. For this model system, we use a microfluidic approach to fabricate polystyrene capsules triggered by a toluene stimulus. However, this active release approach is general and is applicable to diverse polymeric capsule systems; this versatility is demonstrated by extension of our trigger-release scheme to capsules fabricated from a rubberlike block copolymer. The utility of our technique further enhances the potential of these active release capsules for practical application.
我们提出了一种新型的微胶囊，其具有可调谐的主动释放机制。这些胶囊由增塑刺激触发，该刺激会引起聚合物膜从固态到流态的相转变；此后，通过胶囊壁上的缺陷将货物主动推出胶囊，释放动力学具有可控性。通过调整增塑刺激的量来调整膜流动性的程度，使我们能够获得从亚秒级突然爆发释放到几分钟内持续缓慢释放包封剂的释放动力学的时间变化。此外，我们通过调整刺激含量、聚合物分子量和胶囊膜厚度来调节集体胶囊触发响应。对于这个模型系统，我们使用微流控方法来制造由甲苯刺激触发的聚苯乙烯胶囊。然而，这种主动释放方法是通用的，适用于各种聚合物胶囊系统；我们的触发-释放方案扩展到由橡胶状嵌段共聚物制成的胶囊，证明了这种多功能性。我们的技术进一步提高了这些主动释放胶囊在实际应用中的潜力。
