Sonic fine-hole forming apparatus

A sonic fine-hole forming apparatus for forming a fine-hole in a surface of a membrane or solid body in a liquid by means of sonic energy, said sonic fine-hole forming apparatus comprising:

• a sonic oscillation section including a sonic transducer;
• a signal generator connected to drive said transducer with a drive signal, said signal generator being configured to produce said drive signal as a waveform which has pointed sharp positive peaks and pointed sharp negative peaks which are asymmetric about a zero axis by virtue of concaved waveform portions being on a first side of the zero axis and not on a second side of the zero axis in a given period of the waveform, and the waveform having linear portions interconnecting said pointed sharp positive peaks with said pointed sharp negative peaks, said sonic oscillation section defining an interior cavity housing a sonic oscillation element and a fluid surrounding said sonic oscillation element, said sonic oscillation element being a sonic transducer configured to deliver sonic energy and driven by said oscillation driving signal generator, said sonic oscillation section having a surface formed by a covering layer defining aid interior cavity and having an electrically insulating property and a sonic transparency, said covering layer being formed to have a thickness of 10 μm or more and to be continuous without openings so as to seal the interior cavity of the sonic oscillation section from an environment exterior to said covering layer and contain the membrane or solid body.