SU-8 photoresist is commonly used in the field of microfabrication as structural material or for molding of microfluidic devices. One major limitation, however, is the difficulty to process partially freestanding SU-8 structures or monolithic closed cavities and channels on-chip. We propose here a simple method for the fabrication of suspended structures, in particular of monolithic SU-8 microchannels. The method is based on the processing of a SU-8 doublelayer. Appropriate modification of the optical properties of the upper layer allows for selective crosslinking in the layer sandwich. This process is suitable for versatile layouts comprising open and hollow SU-8 structures on the same chip.
The paper discusses a multiple variance methodology for measuring the impulse response for small signals of a mildly nonlinear system, i.e., the first-order kernel of a Volterra model. It is shown with theory that using multiple variance inputs and any linear impulse response measurement method, it is possible to accurately estimate the first-order kernel by applying a polynomial interpolation. The values of the input gains that minimize the influence of noise are also determined. The experimental results, considering an emulated scenario, show how the proposed method can be effectively used to accurately estimate the room impulse response in case of nonlinearities in the measurement system.
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