purpose. The application of fluid flow (dynamic) for the physiological nutrition of the tissues and the creation of microenvironmental biomolecular gradients and relevant mechanical cues (e.g., shear stress) is a major aspect of these systems, differentiating them from conventional (static) cell and tissue cultures. This review uses the term MPS exclusively for microfluidic sys- Introduction Definitions and terminologyMicrophysiological systems (MPS) are microfluidic devices capable of emulating human (or any other animal species') biology in vitro at the smallest biologically acceptable scale, defined by t 4 Workshop Report*

We introduced different spirobenzopyran derivatives into poly(N-isopropylacrylamide) gels and evaluated the effects of spontaneous ring-opening rates of the spirobenzopyrans on light-responsive volume change behaviors of the gels. Rates of reswelling from the light-induced shrunken state of the spirobenzopyran-functionalized poly(N-isopropylacrylamide) (p(Sp-NIPAAm)) gels increased with increasing ring-opening rates of spirobenzopyrans in the gels. Bending motion of a rod-like p(Sp-NIPAAm) gel was invoked by local light-irradiation because of asymmetric shrinkage of the gel. Two types of bending motions were observed depending on the reswelling rates of the gels; a gel with a fast reswelling rate was steadily bent only during light-irradiation, whereas another gel with a slow reswelling rate showed a continuous bending motion even after the irradiation. In addition, a sheet-like gel with a fast reswelling rate was operated as a micro-conveyor whose conveying direction was arbitrarily controlled with a light-irradiation.

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A novel functional copolymer was synthesized by modifying poly(N-isopropylacrylamide) with spirobenzopyran. The phase transition properties of the aqueous solution of this copolymer exhibited a logic-gate response to the light irradiation and to increased temperature, which has three different modes depending on the pH of the solution. Especially, a great increase in turbidity was observed even in dilute aqueous solution containing only 0.10 wt % of the copolymer although the copolymer contained spirobenzopyrans by only 1.1 mol %. It was confirmed also that the spirobenzopyran residues were isomerized by the influence of thermally induced phase transition of the same system. The main chain of thermoresponsive polymer and photoresponsive chromophores, which are linked closely together, affected each other.

The quick photoresponse of thin hydrogel layers composed of thermoresponsive poly(N-isopropylacrylamide) with an acrylated spirobenzopyran chromophore incorporated in the polymer backbone is reported. The instant formation of microrelief on a thin hydrogel layer is demonstrated by means of micropatterned light irradiation.