Ferroelectret materials and devices for energy harvesting applications

Abstract

This paper provides an overview of ferroelectret materials for energy harvesting applications. These materials take the form of a cellular compliant polymer with polarised pores that provide a piezoelectric response to generate electrical energy as a result of an applied strain or surrounding vibration. The manufacturing processes used to create ferroelectret polymer structures for energy harvesting are discussed, along with the range of microstructural features and pore sizes that are formed. Their important mechanical, electrical and harvesting performance are then described and compared. Modelling approaches for microstructural design or for predicting the vibrational and frequency dependent response are examined. Finally, conclusions and future perspectives for ferroelectret materials for energy harvesting applications are provided.

Quantification of Free Radicals from Vaping Electronic Cigarettes Containing Nicotine Salt Solutions with Different Organic Acid Types and Concentrations

“…Eight organic acids were chosen for study (Figure ) based on commercial market relevance: benzoic acid (BA), lactic acid (LA), levulinic acid (LVA), succinic acid (SA), salicylic acid (SLA), tartaric acid (TA), malic acid (MA), and citric acid (CA). Of these, benzoic acid and lactic acid are the most commonly used in commercial products at present. ,, The unadjusted pH values for all e-liquid formulations in this study are shown in Table . For studies on radical formation from nicotine salts with different types of organic acid conjugates, e-liquids were formulated at equimolar ratios (1:1) of nicotine to acid and adjusted to neutral pH using sodium hydroxide (NaOH) when required.…”

“…E-liquid solutions containing nicotine salts are now considered the most popular e-liquids to vape with pods and disposable e-cigarette devices. − Unlike e-liquids using freebase nicotine, nicotine salt solutions contain the addition of an organic acid or a mixture of organic acids to form an ionic pair, or a salt, with nicotine. Nicotine salt e-liquid solutions are often available with high concentrations of nicotine (up to 5% or 50 mg/mL) in a mixture of propylene glycol (PG) and vegetable glycerin (VG) . PG and VG are hygroscopic, and thus, water is also one of the most abundant components of e-liquids, present at up to 18 wt % in previously studied vape products. − The pH of commercial nicotine salt e-liquids has been measured to be as low as 3.6, depending on the exact formulation of nicotine salt and ratio of the organic acid to nicotine.…”

“…Although pH measurements of PG/VG-based e-liquids with a potentiometric probe are stable upon addition of water and provide a good approximation of the acid content in solution, the values obtained may not be an accurate quantification of hydronium ion activity due to the lower water environment in e-liquids, even upon dilution. , Freebase nicotine e-liquids are generally available at a 3–20 mg/mL nicotine concentration. The freebase nicotine e-liquids have a measured pH of generally 9–10 in commercial formulations, but such alkaline nicotine formulations can cause a bitter and harsh sensation in the throat when inhaling the aerosol, which have been reported as unappealing to users. − The role of the organic acid is to allow users to vape at higher concentrations of nicotine without compromising taste as well as increasing nicotine delivery deeper into the lungs, resulting in higher overall user satisfaction . Vape users indicate that vaping nicotine salts gave better sensory experiences in terms of smoothness and taste compared to freebase nicotine. , …”

Carbonyls and Aerosol Mass Generation from Vaping Nicotine Salt Solutions Using Fourth- and Third-Generation E-Cigarette Devices: Effects of Coil Resistance, Coil Age, and Coil Metal Material

“…E-liquid formulations with freebase (FB) nicotine, used for the metal coil material study, were prepared with 6 mg/mL nicotine (0.6% FB) in 30% propylene glycol (99%, from Sigma-Aldrich) and 70% vegetable glycerin (≥99.5% from Sigma-Aldrich) by volume (i.e., 30:70 PG/VG), with relevance to commercially available e-liquids. , Solutions were stored at 2–8 °C prior to use. E-liquid formulations with nicotine salts were prepared at 2% (w/w) or 20 mg/mL, with relevance to commercially available e-liquids (20–50 mg/mL concentration range). − Benzoic acid (≥99.5%, from Sigma-Aldrich), was chosen as the acid for the nicotine salt (1:1 molar ratio with nicotine) , due to its popularity in commercial formulations. ,,− …”

“…4th gen pods or pod-mods, which have been recently introduced to the market and are popular among nicotine users, are designed to vape nicotine salts. 4th gen devices are also designed for more efficient nicotine delivery and can be purchased as refillable pods or prefilled pods in a range of formulations containing various organic acid additives and nicotine concentrations. − …”