Dataset Information

Biomimetic Thermal-sensitive Multi-transform Actuator.

ABSTRACT: Controllable and miniaturised mechanical actuation is one of the main challenges facing various emerging technologies, such as soft robotics, drug delivery systems, and microfluidics. Here we introduce a simple method for constructing actuating devices with programmable complex motions. Thermally responsive hydrogels based on poly(N-isopropylacrylamide) (PNIPAM) and its functionalized derivatives (f-PNIPAM) were used to control the lower critical solution temperature (LCST) or the temperature at which the gel volume changes. Techniques for ultra-violet crosslinking the monomer solutions were developed to generate gel sheets with controllable crosslink density gradients that allowed bending actuation to specified curvatures by heating through the LCST. Simple molding processes were then used to construct multi-transform devices with complex shape changes, including a bioinspired artificial flower that shows blossoming and reverse blossoming with a change in temperature.

SUBMITTER: Kim TH

PROVIDER: S-EPMC6536525 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Biomimetic Thermal-sensitive Multi-transform Actuator.

Kim Tae Hyeob TH Choi Jung Gi JG Byun Ju Young JY Jang Yongwoo Y Kim Sung Min SM Spinks Geoffrey M GM Kim Seon Jeong SJ

Scientific reports 20190527 1

Controllable and miniaturised mechanical actuation is one of the main challenges facing various emerging technologies, such as soft robotics, drug delivery systems, and microfluidics. Here we introduce a simple method for constructing actuating devices with programmable complex motions. Thermally responsive hydrogels based on poly(N-isopropylacrylamide) (PNIPAM) and its functionalized derivatives (f-PNIPAM) were used to control the lower critical solution temperature (LCST) or the temperature at ...[more]

PMID: 31133734

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Project description:PurposeThe goal is to provide a sufficient condition for the invertibility of a multi-energy (ME) X-ray transform. The energy-dependent X-ray attenuation profiles can be represented by a set of coefficients using the Alvarez-Macovski (AM) method. An ME X-ray transform is a mapping from N AM coefficients to N noise-free energy-weighted measurements, where N≥2 .MethodsWe apply a general invertibility theorem to prove the equivalence of global and local invertibility for an ME X-ray transform. We explore the global invertibility through testing whether the Jacobian of the mapping J(A) has zero values over the support of the mapping. The Jacobian of an arbitrary ME X-ray transform is an integration over all spectral measurements. A sufficient condition for J(A)≠0 for all A is that the integrand of J(A) is ≥0 (or ≤0 ) everywhere. Note that the trivial case of the integrand equals 0 everywhere is ignored. Using symmetry, we simplified the integrand of the Jacobian to three factors that are determined by the total attenuation, the basis functions, and the energy-weighting functions, respectively. The factor related to the total attenuation is always positive; hence, the invertibility of the X-ray transform can be determined by testing the signs of the other two factors. Furthermore, we use the Cramér-Rao lower bound (CRLB) to characterize the noise-induced estimation uncertainty and provide a maximum-likelihood (ML) estimator.ResultsThe factor related to the basis functions is always negative when the photoelectric/Compton/Rayleigh basis functions are used and K-edge materials are not considered. The sign of the energy-weighting factor depends on the system source spectra and the detector response functions. For four special types of X-ray detectors, the sign of this factor stays the same over the integration range. Therefore, when these four types of detectors are used for imaging non-K-edge materials, the ME X-ray transform is globally invertible. The same framework can be used to study an arbitrary ME X-ray imaging system, for example, when K-edge materials are present. Furthermore, the ML estimator we presented is an unbiased, efficient estimator and can be used for a wide range of scenes.ConclusionsWe have provided a framework to study the invertibility of an arbitrary ME X-ray transform and proved the global invertibility for four types of systems.

Dataset Information

Biomimetic Thermal-sensitive Multi-transform Actuator.

Publications

Biomimetic Thermal-sensitive Multi-transform Actuator.

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