The pinhole formation in photoresist multilayer structure acts as a critical defect for device fabrication. The purpose of this study is pinhole prevention by hydrophilic treatment and analysis of pinhole formation mechanism in terms of surface free energy. A SU-8 photoresist top layer is spin-coated on a SU-8 bottom layer as simplest multilayer structure. Pinholes are formed on bottom layer with no-treatment, however, pinholes cannot be observed when bottom layer is treated by hydrophilic process. Subsequently, the surface free energy and spread coefficients of each SU-8 layer are evaluated. Because the absolute value of spreading coefficient S top is small relatively in case of no-treatment, the pinning phenomenon can be caused by contaminants. A triple point, bottom layer, liquid top layer and air, appears at the pinning area. Air cannot intrude into interface between top-bottom layers due to the spreading coefficient "S air >0". Consequently, the pinhole expansion phenomenon would be dominated by tensional force and viscous-elasticity of liquid top layer. By hydrophilic treatment, surface free energy of bottom layer increases drastically, therefore the pinning phenomenon is prevented because of "S top <<0".

Local heating system composed with micro heater and microfluidic channel is designed and fabricated. Micro heater made of platinum film is formed on a slide glass by radio-frequency magnetron sputtering and lift-off processes. Microfluidic channel is designed to surround the micro heater. A SU-8 epoxy-based negative photoresist is employed as micro channel material and patterned by lithography process. The micro heater has ability to heat over 350 o C at an electric power of 3.12W. Local heating property is evaluated by applying DC electric power. Heating area decreases 61.5% for micro channel filled with water by comparison with empty channel. Temperature of water in the micro channel is rise up 3.5 o C and heat absorption, which is estimated about 275.3µJ. The microfluidic channel with water is an effective method for local hearing. The local heating system with integration of micro heater and channel is one candidate which can apply to various fields such as biological and biomedical tools.

Biopotential is important and sensitive information in order to monitor and control growth condition for living cells. For detecting biopotential change accurately, a stable biocompatible polymer film is required. In this study, a stable surface of a SU-8 film is characterized, and it is possible for applying to a cover material of electrode surface or an element of a biological implanted device. Surface potential V SU-8 of a SU-8 film is measured by making a metallic electrode contact. As a standard equilibrium, V SU-8 indicates exponential decreasing to reach at +21mV. Biopotential V bio of plant cells indicates large potential change for 10 to 42mV range. This potential change means an individualistic signal of living cells. By combination of a SU-8 film and living cells, it is capable of obtaining accurate and effective data.