Shape-memory surfaces with on-demand, tunable nanopatterns are developed to observe time dependent changes in cell alignment using temperature-responsive poly(ϵ-caprolactone) (PCL) films. Temporary grooved nanopatterns are easily programmed on the films and triggered to transition quickly to permanent surface patterns by the application of body heat. A time-dependent cytoskeleton remodeling is also observed under biologically relevant conditions.

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We propose a new approach to fabricate reversible self-bending actuators utilizing a photo-triggered pH jump reaction. A photo-initiated proton-releasing agent of o-nitrobenzaldehyde (NBA) was successfully integrated into bilayer hydrogels composed of a polyacid layer, poly(Nisopropylacrylamide-co-2-carboxyisopropylacrylamide) (P(NIPAAm-co-CIPAAm)) and a polybase layer, poly(N-isopropylacrylamide-co-N,N 0 -dimethylaminopropylacylamide) (P(NIPAAm-co-DMAPAAm)), where the adhesion of both layers was achieved via electrophoresis of semiinterpenetrating polyelectrolyte chains. The NBA-integrated bilayer gels demonstrated quick proton release upon UV irradiation, allowing the pH within the gel to decrease below the volume phase transition pH in 30 seconds. By controlling the NBA concentration and the gel thickness, the degrees and the kinetics of bending were easily controlled. Reversible bending was also studied with respect to the NBA concentration in response to 'on-off' UV irradiation. Additionally, self-bending of the non-UV irradiated region of the gel was also achieved because the generated protons gradually diffused toward the non-irradiated region. The proposed system can be potentially applied in the fields of mechanical actuators, controlled encapsulation and drug release, robotics and microfluidic technologies because control over autonomous motion by both physical and chemical signals is essential as a programmable system for real biomedical and nano-technological applications.

Poly(N-isopropylacrylamide) (PIPAAm) of controlled molecular weight was densely grafted onto glass capillary lumenal surfaces using surface-initiated atom transfer radical polymerization (ATRP). Temperature-dependent changes of these thermoresponsive brush surfaces with hydrophobic steroids were investigated by exploiting thermoresponsive aqueous wettability changes of the polymer-modified surfaces in microfluidic systems. IPAAm was polymerized on ATRP initiator-immobilized glass surfaces using CuCl/CuCl(2)/tris(dimethylaminoethyl)amine (Me(6)TREN) as an ATRP catalyst in water at 25 degrees C. PIPAAm graft layer thickness and its homogeneity on glass surfaces are controlled by changing ATRP reaction time. Aqueous wettability changes of PIPAAm-grafted surfaces responses drastically changed to both grafted polymer layer thickness and temperature, especially at lower temperatures. Temperature-responsive surface properties of these PIPAAm brushes within capillary inner wall surfaces were then investigated using capillary chromatography. Effective interaction of hydrophobic steroids with dehydrated, hydrophobized PIPAAm-grafted capillary surfaces was observed above 30 degrees C without any column packing materials. Steroid elution behavior from PIPAAm-grafted capillaries contrasted sharply with that from PIPAAm hydrogel-grafted porous monolithic silica capillaries prepared by electron beam (EB) irradiation wherein significant peak broadening was observed at high-temperature regardless of sample hydrophobicity factors (log P values), indicating multistep separation modes in coated monolithic silica capillaries. In conclusion, thermoresponsive polymer-grafted capillary inner wall surfaces prepared by ATRP exhibit useful temperature-dependent surface property alterations effective to regulate interactions with biomolecules without requirements for separation bed packing materials within the capillary lumen.