RESUMO
Lightweight flexible piezoelectric polymers are demanded for various applications. However, the low instinctively piezoelectric coefficient (i.e. d33) and complex poling process greatly resist their applications. Herein, we show that introducing dynamic pressure during fabrication is capable for poling polyvinylidene difluoride/barium titanate (PVDF/BTO) composites with d33 of ~51.20 pC/N at low density of ~0.64 g/cm3. The melt-state dynamic pressure driven energy implantation induces structure evolutions of both PVDF and BTO are demonstrated as reasons for self-poling. Then, the porous material is employed as pressure sensor with a high output of ~20.0 V and sensitivity of ~132.87 mV/kPa. Besides, the energy harvesting experiment suggests power density of ~58.7 mW/m2 can be achieved for 10 N pressure with a long-term durability. In summary, we not only provide a high performance lightweight, flexible piezoelectric polymer composite towards sustainable self-powered sensing and energy harvesting, but also pave an avenue for electrical-free fabrication of piezoelectric polymers.
RESUMO
BACKGROUND: Unilateral biportal endoscopic discectomy (UBE) is a rapidly growing surgical method that uses arthroscopic system for treatment of lumbar disc herniation (LDH), while percutaneous endoscopic lumbar discectomy (PELD) has been standardized as a representative minimally invasive spine surgical technique for LDH. The purpose of this study was to compare the clinical outcomes between UBE and PELD for treatment of patients with LDH. METHODS: The subjects consisted of 54 patients who underwent UBE (24 cases) and PELD (30 cases) who were followed up for at least 6 months. All patients had lumber disc herniation for 1 level. Outcomes of the patients were assessed with operation time, incision length, hospital stay, total blood loss (TBL), intraoperative blood loss (IBL), hidden blood loss (HBL), complications, total hospitalization costs, visual analogue scale (VAS) for back and leg pain, the Oswestry disability index (ODI) and modified MacNab criteria. RESULTS: The VAS scores and ODI decreased significantly in two groups after operation. Preoperative and 1 day, 1 month, 6 months after operation VAS and ODI scores were not significantly different between the two groups. Compared with PELD group, UBE group was associated with higher TBL, higher IBL, higher HBL, longer operation time, longer hospital stay, longer incision length, and more total hospitalization costs. However, a dural tear occurred in one patient of the UBE group. There was no significant difference in the rate of complications between the two groups. CONCLUSIONS: Application of UBE for treatment of lumbar disc herniation yielded similar clinical outcomes to PELD, including pain control and patient satisfaction. However, UBE was associated with various disadvantages relative to PELD, including increased total, intraoperative and hidden blood loss, longer operation times, longer hospital stays, and more total hospitalization costs.
