Accordingly to the SammyJS docs your route have to be defined as follow :
this.get('#/search/:searchRes', function() {
var searchRes= this.params['searchRes'];
});
As you can fetch the search criteria from the param property I suggest to use this sample :
var searchRes = this.params['searchRes'];
The SammyJS object provides an redirect method.
self.search = function() {
searchRes = $('#search_field').val();
app.redirect("#/search" + "/" + searchRes;);
};
I hope it helps.