Completely foldable electronics based on homojunction polymer transistors and logics.

An increase in the demand for completely foldable electronics has motivated efforts for the development of conducting polymer electrodes having extraordinary mechanical stability. However, weak physical adhesion at intrinsic heterojunctions has been a challenge in foldable electronics. This paper reports the completely foldable polymer thin-film transistors (PTFTs) and logic gate arrays. Homojunction-based PTFTs were fabricated by selectively doping p-type diketopyrrolopyrrole-based semiconducting polymer films with FeCl3 to form source/drain electrodes. The doping process caused a gradual work function change with depth, which promoted charge injection to semiconducting regions and provided a low contact resistance. In addition, the interfacial adhesion in the PTFTs was improved by interfacial cross-linking between adjacent component layers. The electrical performance of the resulting PTFTs was maintained without noticeable degradation even after extreme folding, suggesting that the proposed fabrication strategy can further be applied to various semiconducting polymers for the realization of foldable electronics.

Red fluorescence threshold for assessing the lesion activity of early caries.

PURPOSE: The aim of this study was to determine a red fluorescence threshold for differentiating active from inactive non-cavitated carious lesions. METHODS: Using the Nyvad criteria, 30 human teeth with non-cavitated carious lesions were divided into active lesions (15 teeth) and inactive lesions (15 teeth). Using the blue light of a quantitative light-induced fluorescence-digital camera, the red fluorescence of the lesions was measured as the ΔR value. By live/dead bacterial staining, bacterial viability was calculated as the RatioG/G+R. The ΔR and RatioG/G+R of active and inactive lesions were compared. The relationship between ΔR and RatioG/G+R was also analyzed. The ΔR threshold was determined for the classification of lesion activity, and its validity was tested. RESULTS: The mean ΔR of active lesions was 1.85 fold higher than that of inactive lesions (p < 0.001), and the RatioG/G+R of active lesions was 1.97 fold higher than that of inactive lesions (p < 0.001). There was a significant positive correlation between the ΔR and the RatioG/G+R in non-cavitated carious lesions (p < 0.05). The ΔR threshold for the differentiating non-cavitated carious lesions by activity status was 37.55, and the sensitivity and specificity were both 83.33 %. CONCLUSIONS: A red fluorescence threshold for categorizing non-cavitated carious lesion activity based on microbial metabolic activity was determined. Accurate evaluation of the activity status of non-cavitated carious lesions will assist in diagnosis and treatment planning for patients with dental caries.

Closely Packed Polypyrroles via Ionic Cross-Linking: Correlation of Molecular Structure-Morphology-Thermoelectric Properties.

A series of ionically interconnected polypyrrole (PPy) films are fabricated through two-monomer-connected-precursor polymerization by varying diacid linkers, thereby significantly influencing the crystalline morphology and electrical properties. The structure obtained using 1,5-napthalenedisulfonic acid (PPy-Nap) as a fused aromatic linker exhibits a higher electrical conductivity (∼78 S cm-1) than that (6.7 S cm-1) without a linker (PPy-ref). Cryogenic conductivity measurements reveal that the percolation carrier transport barrier of PPy-Nap is significantly smaller than that of PPy-ref, and the calculated carrier mobility of PPy-Nap is ∼5 times higher compared to PPy-ref. The carrier transport characteristics show a good agreement with morphological data by 2D grazing-incidence X-ray scattering. All PPys have similar doped charge carrier concentrations and, thus, similar Seebeck coefficients (5-8 µV K-1) but very different electrical conductivities. Consequently, PPy-Nap exhibits a higher power factor than that of PPy-ref (0.21 vs 0.043 µW m-1 K-2). The results show that the trade-off relationship between the Seebeck coefficient and electrical conductivity can be overcome by improving crystalline morphology and carrier transport. Thus, both the electrical conductivities and thermoelectric power factors can be improved with maintaining the Seebeck coefficients by enhancing the ordered conductive domains and carrier mobility while maintaining the doping level.

Impact of Terminal End-Group of Acceptor-Donor-Acceptor-type Small Molecules on Molecular Packing and Photovoltaic Properties.

In this study, we synthesized two acceptor-donor-acceptor (A-D-A)-type small molecules (SMs) (P3T4-VCN and P3T4-INCN) with different terminal end-groups (dicyanovinyl (VCN) and 2-methylene-3-(1,1-dicyanomethylene)indanone (INCN)) based on the 1,4-bis(thiophenylphenylthiophene)-2,5-difluorophenylene (P3T4) core that possesses high coplanarity because of intrachain noncovalent Coulombic interactions. We investigated the influence of terminal end-groups on intermolecular packing and the resulting electrical and photovoltaic characteristics. A small change in the end-group structure of the SMs induces a significant variation in the torsional structures, molecular packing, and pristine/blend film morphology. It is noteworthy that the less crystalline P3T4-INCN with tilted conformation is highly sensitive to post-treatments (i.e., additives and annealing) such that it permits facile morphological modulation. However, the highly planar and crystalline P3T4-VCN exhibits a strong tolerance toward processing treatments. After morphology optimization, the fullerene-based bulk-heterojunction solar cell of tilted P3T4-INCN exhibits a power conversion efficiency (PCE) of 5.68%, which is significantly superior to that of P3T4-VCN:PC71BM (PCE = 1.29%). Our results demonstrate the importance of the terminal end-group for the design of A-D-A-type SMs and their sensitivity toward the postprocessing treatments in optimizing their performance.

Unilateral Chewing as a Risk Factor for Hearing Loss: Association between Chewing Habits and Hearing Acuity.

Hearing loss is a common disease in older adults. In order to lower the prevalence of hearing loss, it is important to identify its risk factors. Although some studies have found a relationship between dental status and hearing acuity, few studies have investigated the relationship between unilateral chewing and hearing acuity. This study aimed to assess the effects of unilateral chewing on hearing acuity, with a focus on the risk of hearing loss. Eighty-one participants (aged 51-87 years) were included in the present study. Their chewing habits were determined by visual inspection. The participants were divided into two groups: the Unilateral Chewing Group (UCG; n = 43) and the Bilateral Chewing Group (BCG; n = 38). The preferred chewing side was identified for the UCG. Hearing acuity was determined using pure tone audiometry in a noise-free chamber, conducted at frequencies of 500, 1,000, 2,000, and 4,000 Hz. Hearing loss was defined as a lower hearing threshold greater than 50 dB in either ear at any frequency. Mean hearing thresholds at frequencies of 2,000 and 4,000 Hz were significantly higher, by 5.12 and 15.75 dB, respectively, for the UCG compared to the BCG (P < 0.05). The UCG had a 3.78-fold higher likelihood of suffering from hearing loss (95% confidence interval [CI]: 1.81-7.88). The results suggest that bilateral chewing could be beneficial for preventing hearing loss. This study may provide evidence to support clinical interventions aimed at reducing the risk of hearing loss in patients with unilateral chewing habits.