Cwj mem uas siv lub npas los yob tawm qhov nruab nrab sau ntawv (tus cwj mem lossis tus cwj mem) yog sau ua ke hu ua ballpoint cwjmem. Lub gel cwj mem yog ib qho cuab yeej sau ntawv tshiab uas nrov hauv ntiaj teb tam sim no, thiab tus cwj mem gel yog ib qho cuab yeej sau ntawv uas yog tus cwj mem ballpoint. Lub viscosity ntawm nws qhov nruab nrab sau ntawv yog nyob nruab nrab ntawm dej-raws li (viscosity tsawg dua 10mPa.s) thiab oily (viscosity ntawm 10000-20000mPa.s), thiab lub npe hu ua "neutral" kuj muaj npe tom qab nws.
Gel cwj mem originated nyob rau hauv Nyiv. Nyiv lub SAKURA Co., Ltd. ntse tsim ib yam khoom hu ua "Ballsign" nyob rau hauv 1984 thiab muab tso rau hauv lub lag luam. Xyoo 1988, lwm lub tuam txhab Nyij Pooj, Pentel Co., Ltd. tau tsim cov khoom hu ua "Hybrid" ntawm kev ua lag luam. , tus cwj mem gel yug.
Qhov sib txawv loj tshaj plaws ntawm tus cwj mem gel thiab cov cwj mem ib txwm siv yog tias cov cwj mem ballpoint tau ntim nrog cov roj raws li tus cwj mem, thaum lub gel cwj mem tau ntim nrog dej-raws li gel number case. Raws li cov ntsiab lus tseem ceeb nyob rau hauv Japanese Industrial Standard JIS S 6061: 2005 "Gel Ink Ballpoint Pens thiab Refills", gel number case (neutral ink) yog cov viscosity ntawm tus number case uas txo los ntawm kev txav ntawm lub pob thaum sau ntawv, thiab yog tsis zoo li qub thaum sau ntawv. Tus cwj mem uas nws tus number case viscosity nce siab dua hauv lub xeev yog cov yam ntxwv rheological ntawm tus cwj pwm nruab nrab, uas yog, kev hloov ntawm lub xeev tus cwj mem ua ntej, thaum thiab tom qab sau ntawv yog gel → sol → gel. Neutral ink siv cov xim ua cov xim tseem ceeb. Piv nrog cov tshuaj pleev ib ce, nws muaj lub teeb pom kev zoo, dej tsis kam, kub tsis kam thiab tshuaj lom neeg tsis kam (acid, alkali, muaj zog oxidant, tshuaj dawb, thiab lwm yam), thiab kuj muaj tus cwj mem tsis kam. Nws muaj cov yam ntxwv ntawm cov dej ntws tsis sib xws thiab lub sijhawm ntev kom tshem tawm lub hau, uas tuaj yeem khaws cia mus tas li. Yog li ntawd, gel cwjmem yog cov khoom siv hauv chaw ua haujlwm zoo tshaj plaws, tsis yog rau kev sau ntawv nkaus xwb, tab sis kuj tseem khaws cia ntev ntev ntawm cov ntaub ntawv tseem ceeb.
