Scientists working at the Osaka University in Japan created the first rudimentary cardiac pacemaker by carefully tuning the power output of a laser focused on a heart.
From the abstract:
The intracellular effects of focused near-infrared femtosecond laser irradiation are shown to cause contraction in cultured neonatal rat cardiomyocytes. By periodic exposure to femtosecond laser pulse-trains, periodic contraction cycles in cardiomyocytes could be triggered, depleted, and synchronized with the laser periodicity. This was observed in isolated cells, and in small groups of cardiomyocytes with the laser acting as pacemaker for the entire group. A window for this effect was found to occur between 15 and 30 mW average power for an 80 fs, 82 MHz pulse train of 780 nm, using 8 ms exposures applied periodically at 1 to 2 Hz. At power levels below this power window, laser-induced cardiomyocyte contraction was not observed, while above this power window, cells typically responded by a high calcium elevation and contracted without subsequent relaxation. This laser-cell interaction allows the laser irradiation to act as a pacemaker, and can be used to trigger contraction in dormant cells as well as synchronize or destabilize contraction in spontaneously contracting cardiomyocytes. By increasing laser power above the window available for laser-cell synchronization, we also demonstrate the use of cardiomyocytes as optically-triggered actuators.
Full article: A femtosecond laser pacemaker for heart muscle cells (PDF)
Image caption: Laser actuation of a single cultured cardiomyocyte by irradiation, causing it to contract and stay contracted. The image sequence was taken by phase contrast microscopy and the outline of the cell is highlighted. The laser was focused inside the cell using 30 mW of average power, and 8 ms exposures occurred at 1 Hz intervals. The time sequence is (a) 1 sec, (b) 8 sec, (c) 14.7 sec, and (d) 16.7 sec. (Credit: Osaka University)
(hat tip: Engadget)