This research study designed to look at how well adolescents' and young adults' blood sugars can be controlled with a "closed loop artificial pancreas" using a continuous glucose sensor, an insulin pump, and a computer program that automatically determines how much insulin to give based on the glucose level. The investigators will also study the effect of wearing a small heating patch, the InsuPatch, at the site of insulin infusion, on the ability of the closed loop system to control the blood sugar levels and to reduce the rise in glucose levels after meals.

This is an open-label, single-center, randomized crossover study evaluating the performance of a closed-loop (CL) insulin delivery system using a subcutaneous glucose sensor and an external insulin pump comparing the peak post-prandial glucose levels and the post-prandial glucose AUC during either CL control alone or CL control with the InsuPatch in an inpatient hospital research unit (HRU) setting. The closed loop visit consists of approximately 67 hours over 4 days and 3 nights.

Inclusion Criteria:

1. age 12-40 years
2. clinical diagnosis of type 1 diabetes
3. duration of type 1 diabetes ≥ 1 year
4. HbA1c ≤ 9 %
5. Treated with pump therapy for at least 3 months
6. Body weight > 40 kg

Exclusion Criteria:

1. Insulin resistant (defined as requiring > 1.5 units/kg/day at time of study enrollment
2. Presence of any medical or psychiatric disorder that may interfere with subject safety or study conduct
3. Use of any medications (besides insulin) known to blood glucose levels, including oral or other systemic glucocorticoid therapy. Inhaled, intranasal, or rectal corticosteroid use is allowed along as not given within 4 weeks of admission. Use of topical glucocorticoids is allowable as long as affected skin area does not overlap with study device sites. Subjects using herbal supplements will be excluded, due to the unknown effects of these supplements on glucose control
4. History of poor wound healing, heat sensitivity, or diminished skin integrity.
5. History of hypoglycemic seizure within last 3 months
6. Anemic (low hematocrit), or evidence of renal insufficiency (elevated serum creatinine)
7. Female subjects who are pregnant, lactating, or unwilling to be tested for pregnancy
8. Subjects unable to give consent / permission / assent