This paper introduces a method for fabricating microscale DNA hydrogels using irradiation with patterned light. Optical fabrication allows for the flexible and tunable formation of DNA hydrogels without changing the environmental conditions. Our scheme is based on local heat generation via the photothermal effect, which is induced by light irradiation on a quenching species. We demonstrate experimentally that, depending on the power and irradiation time, light irradiation enables the creation of local microscale DNA hydrogels, while the shapes of the DNA hydrogels are controlled by the irradiation patterns.

The echo state property, which is related to the dynamics of a neural network excited by input driving signals, is one of the well-known fundamental properties of recurrent neural networks. During the echo state, the neural network reveals an internal memory function that enables it to remember past inputs. Due to the echo state property, the neural network will asymptotically update its condition from the initial condition and is expected to exhibit temporally nonlinear input/output. As a physical neural network, we fabricated a quantum-dot network that is driven by sequential optical-pulse inputs and reveals corresponding outputs, by random dispersion of quantum-dots as its components. In the network, the localized optical energy of excited quantum-dots is allowed to transfer to neighboring quantum-dots, and its stagnation time due to multi-step transfers corresponds to the hold time of the echo state of the network. From the experimental results of photon counting of the fluorescence outputs, we observed nonlinear optical input/output of the quantum-dot network due to its echo state property. Its nonlinearity was quantitatively verified by a correlation analysis. As a result, the relation between the nonlinear input/outputs and the individual compositions of the quantum-dot network was clarified.

In networks of spatially distributed fluorescent molecules, Förster resonance energy transfer (FRET) can simultaneously occur over multiple locations and times. Such “FRET networks” have great potential for information-processing and computing applications. To design these applications, the spatiotemporal behavior of FRET networks should be understood. However, studies on their spatiotemporal behavior are scarce. Here, we develop a spatiotemporal model for FRET networks and uncover its temporal characteristic behavior. We theoretically show that our model can generate a distinctive temporal behavior, i.e., the network-induced multicomponent exponential decay of the fluorescence intensity, even for FRET networks of fluorophores with an identical single exponential decay. This theoretical result is supported experimentally using quantum dots.

Anisotropic negative magnetoresistance (MR) parallel and perpendicular to the wires in the regime of quantum interference of hole gas has been investigated in self-organized In 0.2 Ga 0.8 As quantum wires (QWRs) grown on GaAs (221)A substrates by MBE and separated from p-type Si-doped Al 0.35 Ga 0.75 As by an undoped spacer layer of it (thickness L s ) in order to address issues concerning the dimensionality in weak localization (WL) as well as spin-orbit (SO) interaction. For L s = 3 nm, the best fits of the parallel MR to the 2D WL theory have been obtained with τ so ~ 24 ps, being well described by the model of anisotropic 2D WL for strong lateral coupling of the wires. For L s = 20 nm, on the other hand, the best fits to 1D WL theory have been obtained with τ so ~ 150 ps assuming diffusive boundary scattering and the data cannot be fit to 2D WL, being well described by the model of quasi-1D WL. In addition, the data for L s = 10 nm show a featureof the crossover between 2D WL and 1D WL, indicating the intermediate lateral coupling between the wires.