Magnetic-field alignment of lyotropic nematic gels and their memory-effect

Abstract

Many potential applications of anisotropic hydrogels, such as media for tissue engineering and drug delivery, as well as biomimetic actuators, require gels that are macroscopically alignedover macroscopic length scales. Lyotropic nematic gels, a relatively new class of anisotropic hydrogels, may provide a rather simple and robust approach to macroscopically aligned anisotropic hydrogels if the long-range orientational order of the surfactant-based lyotropic liquid crystal is transferred to the order of the gel network segments. Here, we report a kinetically controlled process by which we have successfully fabricated centimeter-sized samples of macroscopically aligned nematic gels by growing a self-assembling fibrillar network in a magnetically aligned lyotropic nematic liquid crystal of rod-like micelles. Once the gel network is fully formed, the macroscopic alignment of the sample is (i) preserved also after removal of the magnetic field and (ii) even recovered after melting and re-forming the nematic liquid crystal. The fibrillar network thus appears to have a remarkable memory effect that stabilizes the anisotropy of the gel and results in very robust anisotropic hydrogels. Follow-up studies will address the responsiveness of the aligned nematic gels.