Different powers of the CO2 laser were tested for applying the thermal treatment, fabricating different microlenses. We observed that the diameter of a microlens is maintained almost constant, while their sag decreases as we increase the BI-D1870 given by the CO2 laser. For a range of powers between 68 and 116 W, microlenses with a diameter around 50 μm and sags between 7 and 0.25 μm were fabricated.
The optical quality of the generated microlenses was determined in terms of their focal length and focal spot size. We obtained microlenses with a focal length between 0.7 and 3 mm and with a focal spot size from 28.8 to 7.8 μm, for different thermal treatments.
AcknowledgmentsThis work has been supported by Consellería de Cultura, Xunta de Galicia, under the contract EM2012/019 Spain.
Biomedical electrode; Laser micromilling; Process parameters; Surface microstructures
From previous reported work, maximum sustainable yield (MSY) is found that the comparisons and performance evaluation of different electrodes have been conducted ,  and . For example, Searle et al.  described a quantitative comparison of three types of bioelectrode (wet, dry and insulating) based on tests involving electrode impedance, static interference and motion artifact induced by various means. Results indicated that the performance of dry and insulating electrodes compared favorably with wet electrodes in many situations. Xu et al.  conducted the performance evaluation of five types of Ag/AgCl bio-electrodes for cerebral EIT. The results show that Ag/AgCl powder electrode had low contact impedance, high SNR, better uniformity and greater stability, suggesting that it was an outstanding candidate for cerebral EIT. Therefore, a great number of investigations indicate that the dry bioelectrode presents a good application prospect in biomedical measurement.