Polyurethane header formed directly on implantable electrical devices

A method of forming a polyurethane header on a device that is implantable in an animal, the method comprising the steps of:

• (a) mixing
• (i) a prepolymer comprising a mixture of a silicon-containing diol of formula (I)
• in which
• R1, R2, R3 and R4 are independently selected from C1-6alkyl;
• R5 and R6 are independently selected from C1-6alkylene;
• R7 is C1-6alkylene, O, S or NR in which R is H or C1-6alkyl;
• and
• n is 1to 3and
• a diisocyanate;
• and
• (ii) a C2-12alkanediol
• (b) injecting the mixture of the prepolymer and the C2-12alkanediol into a vacant cavity of a mould chamber comprising an implantable device that comprises electrodes that project into the vacant cavity, wherein the vacant cavity is shaped to form a header;
• (c) allowing the mixture to cure and form a polyurethane header within the vacant cavity so that the header is secured to the implantable device and embeds the electrodes;
• and
• (d) releasing the implantable device and the formed polyurethane header from the mould.