Development of in-vivo pH Measurement Chip in Digestive System

用于医学诊断和治疗的“饮用”或“体内”生物芯片的开发备受关注。为了创造一种通过感知消化系统中目标的pH值来释放药物的药物传递系统（DDS），我们还计划开发一种“体内”pH值传感芯片。为了实现该芯片，必须开发天线、低压驱动泵、电容型电池及其三维集成。为了提高外部线圈向内部线圈传输数据的信噪比，研究了片剂结构和胶囊结构作为内部线圈。所研究的片剂结构尺寸为直径4.5mm，高度4mm。胶囊结构尺寸直径2.5mm，长度15mm。通过对两种结构的耦合系数的计算，发现片剂结构比胶囊结构更适合。由于传输距离比信号波长短，因此传输信号是由电通量和磁通量携带的。在渗透特性方面，我们采用了电磁耦合传输，而不是电磁波传输。脉冲间隔调制优于移幅键控、移频键控和移相键控。采用0.18mm Si CMOS（互补金属氧化物半导体）工艺，开发了一种有效面积为150 x 150 μm^2的小型通信芯片，允许kbps/Mbps。该通信芯片在108.48MHz时的功耗为0.6 mW。我们开发了能够控制药物释放时间的DDS。我们还研究了药物在胃中漂浮和停留的系统。采用等离子体干燥表面处理可以控制药物释放的时间滞后和速度。

Much attention is paid for the development of "drinking" or "in-vivo" biochips for medical diagnostics and treatments. To create a drug delivery system (DDS) releasing a medicine by sensing the pH of the target in the digestive system, we also plan to develop an "in-vivo" pH sensing chip. To realize the chip, an antenna, a low voltage driven pump, a capacitor type battery and their three-dimensional integration has to be developed. To improve the S/N ratio of transmitting the data from the external coil to the internal coil, a tablet structure and a capsule structure were investigated as the internal coil. The size of the investigated tablet structure is 4.5mm in diameter and 4 mm in height. The size of the capsule structure is 2.5mm in diameter and 15mm in length. From calculating the coupling factor in both structures, it is found that a tablet structure is suitable better than a capsule structure. The transmission signal is carried by electric and magnetic fluxes because the transmission distance is shorter than the signal wavelength. With regard to permeation characteristics, we adopted the electromagnetic coupling transmission rather than the electromagnetic wave transmission. The pulse interval modulation is superior to amplitude shift keying, frequency shift keying and phase shift keying. A small communication chip with an active area of 150 x 150 μm^2 allowing kbps/Mbps has been developed using 0.18mm Si CMOS(complementary metal-oxide semiconductor) process. The communication chip showed consumption power of 0.6 mW at 108.48MHz. We developed DDS enabling to control the time of releasing a medicine. And we also studied the system a medicine floats and remains in stomach. The time lag and the speed of releasing a medicine can be controlled employing surface treatment by plasma dry process.