Applications of Smart Material Sensors and Soft Electronics in Healthcare Wearables for Better User Compliance.

The need for innovation in the healthcare sector is essential to meet the demand of a rapidly growing population and the advent of progressive chronic ailments. Over the last decade, real-time monitoring of health conditions has been prioritized for accurate clinical diagnosis and access to accelerated treatment options. Therefore, the demand for wearable biosensing modules for preventive and monitoring purposes has been increasing over the last decade. Application of machine learning, big data analysis, neural networks, and artificial intelligence for precision and various power-saving approaches are used to increase the reliability and acceptance of smart wearables. However, user compliance and ergonomics are key areas that need focus to make the wearables mainstream. Much can be achieved through the incorporation of smart materials and soft electronics. Though skin-friendly wearable devices have been highlighted recently for their multifunctional abilities, a detailed discussion on the integration of smart materials for higher user compliance is still missing. In this review, we have discussed the principles and applications of sustainable smart material sensors and soft electronics for better ergonomics and increased user compliance in various healthcare devices. Moreover, the importance of nanomaterials and nanotechnology is discussed in the development of smart wearables.

Π-Stacking in Heterodimers of Propargylbenzene with (Fluoro)phenylacetylenes.

The heterodimers of propargylbenzene (PrBz) with phenylacetylene (PHA) and monosubstituted fluorophenylacetylenes (FPHAs) were investigated using electronic and vibrational spectroscopic methods. The vibrational spectra in the acetylenic C-H stretching region show a marginal shift (0-4 cm-1) upon dimer formation, which suggests minimal perturbation of the acetylenic group. The M06-2X/aug-cc-pVDZ calculations indicate that the π-stacked structures are the most stable, followed by other structures. In general, structures incorporating aromatic C-H···π interactions are much higher in energy. The appearance of the spectra and the energy considerations clearly indicate the preference for the π-stacked structures. Furthermore, the observed trend in the stabilization energies for heterodimers with the three FPHAs is inversely proportional to the dipole moments of FPHAs. On the other hand, the absence of any clear trends in the electrostatic component of the interaction energy is attributed to the presence of the methylene group in PrBz.

Dipole Moment Propels π-Stacking of Heterodimers of Fluorophenylacetylenes.

Electronic and vibrational spectroscopic investigations in combination with quantum chemical calculations were carried out to probe the formation of four sets of heterodimers of phenylacetylene with 2-fluorohenylacetylene, 3-fluorophenylacetylene, 4-fluorophenylacetylene, and 2,6-difluorophenylacetylene. The interaction of phenylacetylene with fluorophenylacetylenes leads to marginal (2-9 cm-1) red-shifts in the acetylenic C-H stretching frequencies of fluorophenylacetylenes, which suggests that constituent monomers are minimally perturbed in the heterodimer. On the other hand, the density-functional-theory-based calculations indicate that π-stacked structures outweigh other structures incorporating C-H···π and C-H···F interactions by about 8 kJ mol-1 or more. The IR spectra in the acetylenic C-H stretching region were interpreted based on the perturbed dipole model, which suggests formation of predominantly antiparallel π-stacked structures, propelled by dipole moment. However, the energy decomposition analysis suggests that among stabilizing components dispersion dominates, while electrostatics plays a pivotal role in the formation of the π-stacked structures. Interestingly, the ability of 2-fluorophenylacetylene and 2,6-difluorophenylacetylene to π-stack differs significantly, even though both of them have almost identical dipole moments and the dipole moment propels the formation of π-stack structures. These results suggest π-stacking transcends the classical electrostatic description in terms of dipole moment.

The propargylbenzene dimer: C-H···π assisted π-π stacking.

The propargylbenzene dimer was investigated using mass selected electronic and infrared spectroscopy in combination with quantum chemical calculations. The IR spectrum in the acetylenic C-H stretching region indicates that the two propargylbenzene units in the dimer are in an almost identical environment. The stabilization energies calculated at various levels of theory predict that the anti-parallel structure is the most stable isomer. The observed spectra are assigned to π-stacked structures which incorporate C-H···π interaction. The symmetry-adapted perturbation theory (SAPT) based energy decomposition analysis reveals that electrostatics contributes around 35% while the rest is due to dispersion. Comparison with the phenylacetylene and toluene dimers indicates that the higher stabilization energy of the PrBz dimer can be attributed to the synergy between the π-π stacking and C-H···π interactions.

Studies of structural isomers o-, m-, and p-fluorophenylacetylene by two-color resonant two-photon mass-analyzed threshold ionization spectroscopy.

We report the vibrational spectra of o-fluorophenylacetylene (OFPA), m-fluorophenylacetylene (MFPA), and p-fluorophenylacetylene (PFPA) in the electronically excited S1 and cationic ground D0 states. These new data show that the relative location of the fluorine atom with respect to the acetylenic group can influence the transition energy and molecular vibration. The adiabatic ionization energies of these structural isomers follow the order: PFPA < OFPA < MFPA. It is found that the molecular geometries of these molecules in the D0 state resemble those in the S1 state. Detailed spectral analysis suggests that the in-plane ring deformation vibrations are slightly "harder" in the D0 state than the corresponding ones in the S1 state.

2-(2'-Pyridyl)benzimidazole as a fluorescent probe of hydration of nafion membranes.

2,2'-(Pyridyl)benzimidazole is used as a probe to explore proton transfer through nafion membranes. The probe marks the availability of water in native as well as cation-exchanged membrane. Using steady state and time-resolved fluorescence studies, it has been shown that the rotation of the pyridyl and benzimidazole rings with respect to each other, which is ultrafast in higher water contents, is hindered as the water content in the membranes is decreased. In cation-exchanged membranes, it is observed that the formation of the ESPT (excited state proton transfer) state is reduced to a large extent. Thus, it may be inferred that the proton transport is observed to be hindered even in molecular dimensions of one water molecule thereby bolstering the contention that it may not be essential for water channels to break for proton conductivity to decrease.