Surgical instrument

An electrosurgical instrument comprising:

• an instrument shaft comprising a first transmission line for conveying microwave electromagnetic (EM) energy;
• a distal end assembly arranged at a distal end of the instrument shaft to receive the microwave EM energy from the first transmission line, the distal end assembly comprising:
• a pair of jaws that are movable relative to each other to open and close a gap between opposing inner surfaces thereof;
• wherein a first jaw of the pair of jaws comprises:
• an energy delivery structure arranged to emit the microwave EM energy into the gap between the opposing inner surfaces, the energy delivery structure comprising:
• a dielectric substrate having a top surface that is exposed at the gap between the opposing inner surfaces, and an under surface on an opposite side of the dielectric substrate from the top surface;
• a ground conductive layer on the under surface;
• and
• an active conductive strip on the top surface;
• and
• wherein the first jaw comprises an electrically conductive outer shell, the outer shell being electrically connected to the ground conductive layer.

An electrosurgical instrument comprising:

• an instrument shaft arranged to convey radiofrequency (RF) EM energy;
• a distal end assembly arranged at a distal end of the instrument shaft to receive the RF EM energy from the instrument shaft, the distal end assembly comprising:
• a pair of jaws that are movable relative to each other to open and close a gap between opposing inner surfaces thereof;
• wherein a second jaw of the pair of jaws comprises:
• an electrically conductive outer shell;
• and
• an active electrode arranged on an outer surface of the jaw, the active electrode being for delivering RF energy to biological tissue, the active electrode being electrically isolated from the electrically conductive outer shell,
• wherein the electrically conductive outer shell is grounded to form a return electrode for the RF energy, and
• wherein the active electrode is substantially flush with the outer surface of the jaw.