Development of in-vivo pH Measurement Chip in Digestive System

用于医疗诊断和治疗的“饮品”或“体内”生物芯片的开发备受关注。为了创造一种药物释放系统(DDS)，通过感知消化系统中目标对象的PH值来释放药物，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、电容型电池以及它们的三维集成。为了提高从外线圈向内线圈传输数据的S/N比，研究了片状结构和胶囊结构作为内线圈。所研究的片剂结构的尺寸为直径4.5 mm，高度4 mm。胶囊结构尺寸为直径2.5 mm，长15 mm。通过对两种结构的耦合系数的计算，发现片状结构比胶囊结构更合适。由于传输距离小于信号波长，传输信号由电磁通量携带。对于渗透特性，我们采用了电磁耦合传输，而不是电磁波传输。脉冲间隔调制优于幅移键控、频移键控和相移键控。采用0.18 mm硅互补金属氧化物半导体工艺研制了一种工作面积为150x150μm^2的小型通信芯片，可实现kbps/Mbps的传输。该通信芯片在108.48 MHz下的功耗为0.6 mW。我们开发了DDS，能够控制药物的释放时间。我们还研究了药物漂浮并留在胃里的系统。采用等离子体干燥工艺对药物进行表面处理，可以控制药物释放的时滞和速度。

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.