Highly Exfoliated Boron Nitride Nanosheets via Carboxyl Nanocellulose for Thermally Conductive Nanocomposite Films

The continuous development of electronic devices toward high-power and integrated directions has led to an increasing demand for renewable polymer composite materials with high thermal conductivity and electrical insulation to solve the problem of overheating in electronic devices. Cellulose is inherently insulating, with insufficient thermal conductivity. Although boron nitride nanosheets (BNNSs) have excellent thermal conductivity, hexagonal boron nitride (h-BN) ligands in their raw state are prone to aggregation, which limits their performance. In this work, h-BN was first ball-milled and amino-modified, and then, carboxylated nanofibrillated cellulose (COOH-CNF) was used to disperse the BNNSs. With the help of amide bonding, the BNNSs were uniformly dispersed in the nanocellulose (CNF) matrix; this reduced the aggregation and the presence of voids between the BNNSs and promoted the construction of effective thermal channels. The resulting composite slurry was stably dispersed and could be filtered to form a film; the best overall performance was achieved for a BNNS loading of 30% with a thermal conductivity (TC) of 9.00 W·m–1·K–1 (pure CNF 1.88 W·m–1·K–1). In addition, the volume resistivity reached 9.38 × 1013 Ω·cm (pure CNF of 2.53 × 1013 Ω·cm) and the electrical strength reached 22.67 kV·mm (17.04 kV·mm for CNF). Our results showed that the BNNS-CNF composite film had high TC and excellent insulating properties; therefore, its application in the thermal management of electronic devices has broad application prospects

Capillary blood for point-of-care testing

<p>Clinically, blood sample analysis has been widely used for health monitoring. In hospitals, arterial and venous blood are utilized to detect various disease biomarkers. However, collection methods are invasive, painful, may result in injury and contamination, and skilled workers are required, making these methods unsuitable for use in a resource-limited setting. In contrast, capillary blood is easily collected by a minimally invasive procedure and has excellent potential for use in point-of-care (POC) health monitoring. In this review, we first discuss the differences among arterial blood, venous blood, and capillary blood in terms of the puncture sites, components, sample volume, collection methods, and application areas. Additionally, we review the most recent advances in capillary blood-based commercial products and microfluidic instruments for various applications. We also compare the accuracy of microfluidic-based testing with that of laboratory-based testing for capillary blood-based disease diagnosis at the POC. Finally, we discuss the challenges and future perspectives for developing capillary blood-based POC instruments.</p