Teflon fep

Hydrophilic coating of microcapillary film MCF was produced by Lamina Dielectrics Ltd (Billingshurst, West Sussex, UK) from Teflon® FEP (Dupont, USA) using a melt-extrusion process, 29 and consisted of an array of 10 parallel microcapillaries with a mean hydraulic diameter of 206 ± 12.6 μm. The fluoropolymer MCF was subsequently modified by coating the inner surface of the microcapillaries with a permanent hydrophilic layer of PVOH. This involved recirculating at a flow rate of 50 mL h -1 overnight a volume of 100 mL of a 5 mg mL -1 solution of poly(vinyl alcohol) (PVOH) in water (MW 13 000-23 000, >98% hydrolysed for ABO blood grouping experiments; MW 146 000-186 000, >99% hydrolysed for bacteria and MIC testingall from Sigma-Aldrich, UK). A 6 m long fluoropolymer MCF was attached to a FPLC P-500 Pharmacia Biotech pump using Upchurch flangeless tube fittings (Kinesis, UK). The PVOH coating was then crosslinked with glutaraldehyde by manually filling the MCF with a freshly prepared 5 mg mL -1 of PVOH solution containing 5 mM of glutaraldehyde (Sigma-Aldrich, UK) and 5 mM HCl (Sigma-Aldrich, UK) for 2 hours at 37 °C, followed by manual washing with water and drying with multiple changes of air using a 50 mL syringe.

The MCF material was manufactured by Lamina Dielectrics Ltd (Billingshurst, West Sussex, UK) from Teflon® FEP (Dupont, USA) and consists of an array of 10 parallel microcapillaries with a mean hydraulic diameter of 206 ± 12.6 μm (34) . The raw MCF strips are hydrophobic (28) , therefore they would require a pressure driven flow for sample loading; however in this work the MCF strips were made hydrophilic by coating the inside of each capillary with an hydrogel, poly(vinyl alcohol) (PVOH) (28) . In this way the MCF strips could be filled simply by capillary action ('dip stick' mode). During the coating procedure 100 mL of an aqueous solution of PVOH (MW 13 000-23 000, >98 % hydrolysed from Sigma-Aldrich, Dorset, UK) with concentration of 5 mg/mL was recirculated through a 6 m long MCF at a flowrate of 50 mL/h for 12-15 hrs using a FPLC P-500 Pharmacia Biotech (Piscataway, USA) pump and Upchurch flangeless tube fittings (Kinesis, Saint Neots, United Kingdom). After that, the PVOH coating was crosslinked with glutaraldehyde by manually filling the MCF strip with a freshly prepared solution of PVOH (5 mg/mL) containing 5 mM of glutaraldehyde (Sigma-Aldrich, UK) and 5 mM HCl (Sigma-Aldrich, UK). The solution was kept inside the strips for 2 hours at 37 °C, after which the MCF strips were manually washed and dried with air using a 50 mL syringe (34) .