An Exploratory Trial Investigating the Safety and Efficacy of Fast-acting Insulin Aspart in a Closed-loop Insulin Delivery System (Bionic Pancreas) in Adults With Type 1 Diabetes

The iLet™ is a new insulin pump that is programmed to work with a Continuous Glucose Monitoring (CGM) device. This is to give participants insulin automatically. The CGM device is already available for sale. The iLet™ is not yet approved for use. Fast-acting insulin aspart is a type of insulin that doctors can already prescribe for use with insulin pens, but not for use in an insulin pump. This study is to test how safe fast acting insulin aspart is when used with different insulin delivery settings in the iLet™ in people with type 1 diabetes. Participants will get fast-acting insulin aspart as participants' insulin and use the iLet™ as participants' insulin pump with a CGM device. Participants' iLet™ will be set to 2 different insulin delivery settings for 7 days on each setting. The setting participants get first is decided by chance. The study will last for about 5 to 9 weeks. Participants will have 4 visits and 1 phone contact with the study or staff.