Description

The information and models provided in this upload are the result of a nine-month Mechanical Engineering capstone at the University of Washington. The goal of this project was to create a quantitative, accurate means of measuring capillary refill time (https://www.nlm.nih.gov/medlineplus/ency/article/003394.htm) (CRT) in children. The provided solution uses a clothespin-like apparatus and a smartphone camera to apply blanching pressure to a subject's fingertip and detect changes in skin color.The procedure closely follows that of the nail blanch (https://www.nlm.nih.gov/medlineplus/ency/imagepages/9154.htm) test, substituting the hand and eye of an clinician with a mechanical presser and an onboard video-processing algorithm. The device consists of three seperate 3D-printable entities and a companion Android application. Some additional components are required to complete the final device: the smartphone itself (an HTC Desire 620G Dual Sim), a small 12 in-lb torsion spring, and a 21.4 mm x 21.4 mm x 11.75 mm block of clear plastic. The printable components are as follows: Pressure applicator. Clothespin-like in form and function. Uses a torsion spring to provide a known, repeatable amount of force. Phone case. Tailored for a loose press fit onto HTC Desire. Mounting points (paired journal bearings) for presser located on back of case. Empty windowframe underneath rear camera for clear plastic window to drop into. Pin. Joins applicator to phone case and allows for rotation. An early version of the Android app used to interface with the device is available. The app prompts the user to apply and release pressure, takes a video of the finger during and after the process, and performs colorimetric analysis on the video data to determine CRT. Please contact creator personally for further information.